Dissertations / Theses: 'Code de Gold'

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Saito, Masato, Takaya Yamazato, Hiraku Okada, Masaaki Katayama, and Akira Ogawa. "Generation of Sets of Sequences Suitable for Multicode Transmission in Quasi-Synchronous CDMA Systems." IEICE, 2001. http://hdl.handle.net/2237/7223.

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Lynch, Peter James. "Computer simulation of Gold code phase modulation in ocean acoustic tomography." Thesis, Monterey, California. Naval Postgraduate School, 1989. http://hdl.handle.net/10945/25772.

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陳翠玲 and Chui-ling Chan. "Synthesis and luminescence studies of homo- and heteronuclear complexes of gold and copper." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31238178.

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Zhengxuan, Zhang, Kou Yanhong, and Zhang Qishan. "DESIGN OF A SOFTWARE RADIO GPS RECEIVER." International Foundation for Telemetering, 2005. http://hdl.handle.net/10150/605032.

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ITC/USA 2005 Conference Proceedings / The Forty-First Annual International Telemetering Conference and Technical Exhibition / October 24-27, 2005 / Riviera Hotel & Convention Center, Las Vegas, Nevada
The GPS receiver based on software radio technology is a kind of general purpose GPS signal processing platform which makes use of advanced design ideas and advanced design tools nowadays. We used FPGA device and lots of necessary peripherals such as DSP and PCI controller in our design to promote flexibility and practicability effectively. Various fast acquisition means and accurate tracking algorithms could be realized, improved and validated on this platform, besides basic GPS receiver function.

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Bouvier, des Noes Mathieu. "Détection itérative des séquences pseudo-aléatoires." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAT068/document.

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Les séquences binaires pseudo-aléatoires sont couramment employées par les systèmes de transmissions numériques ou des mécanismes de chiffrement. On les retrouve en particulier dans les transmissions par étalement de spectre par séquence direct (e.g. 3G ou GPS)) ou pour construire des séquences d'apprentissage pour faciliter la synchronisation ou l'estimation du canal (e.g. LTE). Un point commun à toutes ces applications est la nécessité de se synchroniser avec la séquence émise. La méthode conventionnelle consiste à générer la même séquence au niveau du récepteur et la corréler avec le signal reçu. Si le résultat dépasse un seuil pré-défini, la synchronisation est déclarée acquise. On parle alors de détection par corrélation.Cette thèse aborde une autre voie : la détection des séquences binaires pseudo-aléatoire par des techniques de décodage canal. Ceci permet par exemple de détecter des séquences longues (e.g. de période 242), contrairement aux techniques par corrélation qui sont trop complexes à implémenter. Cela nécessite néanmoins que le récepteur connaisse au préalable le polynôme générateur de la séquence.Nous avons montré que le décodage d'une séquence pseudo-aléatoire est une problématique du type 'détecte et décode'. Le récepteur détecte la présence de la séquence et simultanément estime son état initial. Ceci correspond dans la théorie classique de la détection à un détecteur de type GLRT qui ne connaît pas la séquence émise, mais qui connaît sa méthode de construction. L'algorithme implémente alors un GLRT qui utilise un décodeur pour estimer la séquence reçue. Ce dernier est implémenté avec un algorithme de décodage par passage de messages qui utilise une matrice de parité particulière. Elle est construite avec des équations de parités différentes, chacune ayant un poids de Hamming valant t.Il correspond au nombre de variables participants à l'équation.Les équations de parité sont un constituant indispensable du décodeur. Nous avons donné leur nombre pour les m-séquences et les séquences de Gold. Pour le cas particulier des séquences de Gold, nous avons calculé le nombre d'équations de parité de poids t=5 lorsque le degré du polynôme générateur r est impair. Ce calcul est important car il n'y a pas d'équations de parité de poids t < 5 lorsque r est impair. Le nombre d'équations de parité est aussi utilisé pour estimer le degré minimal des équations d'un poids t donné. Nous avons montré que le modèle de prédiction estime correctement la valeur moyenne du degré minimal de l'ensemble des séquences de Gold. Nous avons néanmoins mis en évidence une grande variabilité du degré minimal des séquences autour de cette valeur moyenne.Nous avons ensuite identifié les ensembles absorbants complets de plus petite taille lorsque le décodeur emploie plusieurs polynômes de parité. Ces ensembles bloquent la convergence du décodeur lorsque celui-ci est alimenté avec du bruit. Ceci évite les fausses alarmes lors du processus de détection. Nous avons montré que des cycles 'transverses' détruisent ces ensembles absorbants, ce qui génère des fausses alarmes. Nous en avons déduit un algorithme qui minimise le nombre de cycles transverses de longueur 6 et 8, ce qui minimise la probabilité de fausse alarme lorsque le poids des équations de parité vaut t=3. Notre algorithme permet de sélectionner les équations de parité qui minimisent la probabilité de fausse alarme et ainsi réduire notablement le temps d'acquisition d'une séquence de Gold.Nous avons enfin proposé deux algorithmes de détection du code d'embrouillage pour les systèmes WCDMA et CDMA2000. Ils exploitent les propriétés des m-séquences constituant les séquences de Gold, ainsi que les mécanismes de décodage par passage de messages. Ces algorithmes montrent les vulnérabilités des transmissions par étalement de spectre
Pseudo-random binary sequences are very common in wireless transmission systems and ciphering mechanisms. More specifically, they are used in direct sequence spread spectrum transmission systems like UMTS or GPS, or to construct preamble sequences for synchronization and channel estimation purpose like in LTE. It is always required to synchronize the receiver with the transmitted sequence. The usual way consists in correlating the received signal with a replica of the sequence. If the correlation exceeds a predefined threshold, the synchronization is declared valid.This thesis addresses a different approach: the binary sequence is detected with a forward error correction decoding algorithm. This allows for instance to detect very long sequences.In this thesis, we show that decoding a pseudo-random sequence is a problematic of the kind ‘detect and decode'. The decoder detects the presence of the transmitted sequence and simultaneously estimates its initial state. In conventional detection theory, this corresponds to a GLRT detector that uses a decoder to estimate the unknown parameter which is the transmitted sequence. For pseudo-random sequences, the decoder implements an iterative message-passing algorithm. It uses a parity check matrix to define the decoding graph on which the algorithm applies. Each parity check equation has a weight t, corresponding to the number of variables in the equation.Parity check equations are thus an essential component of the decoder. The decoding procedure is known to be sensitive to the weight t of the parity check equations. For m-sequences, the number of parity check equations is already known. It is given by the number of codewords of weight t of the corresponding Hamming dual code. For Gold sequences, the number of parity check equations of weight t = 3 and 4 has already been evaluated by Kasami. In this thesis we provide an analytical expression for the number of parity check equations of weight t = 5 when the degree of the generator polynomial r is odd. Knowing this number is important because there is no parity check equation of weight t < 5 when r is odd. This enumeration is also used to provide an estimation of the least degree of parity check equations of weight t.We have then addressed the problem of selecting the parity check equations used by the decoder. We observed the probability of false alarm is very sensitive to this selection. It is explained by the presence or absence of absorbing sets which block the convergence of the decoder when it is fed only with noise. These sets are known to be responsible for error floor of LDPC codes. We give a method to identify these sets according to the parity check equations used by the decoder. The probability of false alarm can increase dramatically if these absorbing sets are destroyed. Then we propose an algorithm for selecting these parity check equations. It relies on the minimization of the number of cycles of length 6 and 8. Simulation show that the algorithm allows to improve significantly the probability of false alarm and the average acquisition time.Eventually, we propose 2 algorithms for the detection of the scrambling codes used in the uplink of UMTS-FDD and CDMA2000 systems. They highlights a new vulnerability of DSSS transmission systems. It is now conceivable to detect these transmission if the sequence's generator is known

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Tyrrell, Christina Holly. "A Lateral Flow Smart Phone Image Analysis Diagnostic." DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/1083.

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A low cost compact diagnostic has many implications in today’s society. Smart phone technology has exponentially grown and with it the imaging capabilities associated with smart phones. The goals of this research are i) to determine the feasibility of combining in the field smart phone images with color dependent assay results, ii) to develop a MatLab® image analysis code to analyze these results, and iii) compare limits of detection between the un-aided eye and MatLab® image analysis software. Orange G dye is used to create a stock solution and subsequent titers for analysis. Autocad is used to design an assay platform of 10x10 wells that are printed via a Xerox® Phaser printer with wax ink onto nitrocellulose paper. Dilutions are performed and pipetted into the wells. The image analysis code is used to determine hue, saturation, and value (HSV) values of wells. A limit of detection study using the dye is performed. HSV values are used to form calibration curves. The resulting curve fit equations are then integrated into the image analysis code to determine dye concentration. Finally, the complete capability is demonstrated by using an analogous 10x10 well experimental nitrocellulose sheet, which included a follow-up experiment via a spot check analysis. This study illustrates the feasibility of a low cost image analysis as a tool for lateral flow assay diagnostic versus the unaided eye. Future work includes using this protocol in conjunction with a lateral flow immunoassay and developing an application for the analysis.

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Rydlo, Štěpán. "Detekce dronu v prostoru." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2019. http://www.nusl.cz/ntk/nusl-403154.

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This master thesis purposes is create localization system using software defined radio. The purpose of this thesis is to create new localization system, which will be independent of existing systems. To create a localization system, we will use ADALM-PLUTO device to send and receive radio signals. This work contains a decription of serval possibilities how to create the localization system and description of their comunication.

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Shah, Julin Mukeshkumar. "Compressive Sensing Analog Front End Design in 180 nm CMOS Technology." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1440381988.

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Dubreuil, Laurent. "Amélioration de l'étalement de spectre par l'utilisation de codes correcteurs d'erreurs." Limoges, 2005. https://aurore.unilim.fr/theses/nxfile/default/3964483f-5b1f-41dd-b862-6c3d029c0d41/blobholder:0/2005LIMO0041.pdf.

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Dans cette thèse, nous étudions un système de communication nommé étalement de spectre. Le principe de ce système consiste à répartir l'énergie du signal à émettre sur une bande de fréquence plus large que celle réellement nécessaire à la transmission du signal utile. Le fonctionnement de l'étalement de spectre est basé sur l'utilisation de "séquences d'étalement" ayant de bonnes propriétés de corrélation. Dans cette thèse, nous introduisons des codes correcteurs d'erreurs pour améliorer l'efficacité de l'étalement du signal. L'objectif de cette thèse est de déterminer l'efficacité de cette méthode et les critères de choix des codes correcteurs d'erreurs. Le nombre maximum d'utilisateurs dépend du choix du code correcteur d'erreur utilisé mais aussi de la séquence d'étalement utilisée. Une synthèse de l'étalement de spectre et du CDMA (Code Division Multiple Access) est présentée dans une première partie. Des limites théoriques sont données et des limites physiques sont posées. Puis deux systèmes à étalement de spectre utilisant des séquences d'étalement différentes sont présentés et comparés. Le système le plus performant, aussi bien théorique que pratique, est l'étalement de spectre "à déphasage multiple". La dernière partie présente divers codes correcteurs d'erreur et détermine celui qui maximise le nombre d'utilisateurs. Toutefois, pour un taux d'erreur binaire résiduel inférieur à 10-3 et un facteur d'étalement de 31, le nombre maximum d'utilisateurs obtenu en pratique est de 23 avec l'utilisation de code correcteurs d'erreur et de 7 sans, tandis que du point de vue théorique on en espère 45
In this thesis we study a communication system named spread spectrum. The principle of this system consists in distributing the energy of the signal to transmit on a frequency band broader than what is really necessary to the transmission of the useful signal. Spread spectrum is based on using "spreading sequences" having good properties of correlation. In this thesis we introduce error correcting codes to improve the efficiency of the spreading signal. The aim of this thesis is to determine the efficiency of this method and the selection criteria of the error-correcting codes to use. The maximum number of users depends on the choice of the error-correcting code used but also on the spreading sequence used. A synthesis of the spread spectrum and CDMA (Code Division Multiple Access) are presented in a first part. Theoretical limits are given and physical limits are posed. Next two systems of spread spectrum using different spreading sequence are presented and compared. The most powerful system, theoretically as well as practically, is the spread spectrum "with multiple dephasing". The last part presents various error-correcting codes and determines which one maximizes the number of users. However, for a binary error rate residual lower than 10-3 and a spreading factor of 31 the maximum number of users obtained in practice is 23 with using error-correcting code and 7 without it, while from the theoretical point of view the expected number is 45

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Selmi, Ikhlas. "Optimisation de l'infrastructure d'un système de positionnement indoor à base de transmetteurs GNSS." Phd thesis, Institut National des Télécommunications, 2013. http://tel.archives-ouvertes.fr/tel-00919772.

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Dans le but de fournir un service GNSS (Global Navigation Satellite System) de localisation continu et disponible partout, les systèmes utilisant des pseudolites et des répéteurs semblent être des solutions pertinentes pour la localisation en indoor. Le système à répélites, inspiré de ces deux méthodes (répéteurs et pseudolites), est aussi proposé pour résoudre cette problématique. Les répélites sont des transmetteurs locaux qui, installés en intérieur, formeront une constellation locale. Ils émettent tous un signal GNSS unique mais déphasé par un délai spécifique à chacun d'eux. Ces délais sont nécessaires pour distinguer les différents signaux reçus au niveau du récepteur. Les travaux de cette thèses sont réalisés dans le cadre du système à répélites et dans l'objectif d'améliorer son architecture et de réduire ses interférences inter-système. En effet, l'architecture du système (un peu encombrante) et les interférences éventuelles avec les signaux satellitaires reçus par un récepteur placé à l'extérieur font partie des inconvénients de ce système. On cherche donc à traiter ces deux difficultés de façon à minimiser leurs effets. Dans une première partie, on étudie les différents codes GNSS existants dans la littérature ainsi que les techniques de modulation employées. Ceci nous mène à proposer des codes ayant un niveau d'interférence équivalent à la référence GPS (obtenue entre deux codes GPS) pour les bandes L1 de GPS et G1 de Glonass. Dans une seconde étape, on développe la modulation IMBOC (Indoor Modified Binary Offset Carrier) pour générer de nouveaux codes caractérisés par des niveaux d'interférence réduits (comparés à la référence GPS). Parmi ces codes il y a deux catégories : ceux qui sont adaptés aux systèmes à répélites (émettant un code unique) et ceux qui sont adaptés aux systèmes pseudolites. Une étude théorique et des simulations des niveaux d'interférences pour les codes émis dans la bande GPS et Glonass sont réalisées pour déterminer les gains en termes de niveaux de bruit. Ce gain (par rapport à la référence GPS) en puissance d'interférence s'élève à 16 dB pour Glonass et 20 dB pour GPS. Pour valider les performances de ces codes, on génère les signaux IMBOC et on observe les interférences réelles qu'ils induisent sur un récepteur GPS recevant un signal satellitaire. Dans la deuxième partie, on utilise la fibre optique pour transmettre le signal du générateur jusqu'aux répélites et pour créer les délais initiaux par propagation du signal dans des bobines de fibre. Ainsi on remplace les câbles coaxiaux et les montages électroniques (de déphasage) par des bobines de fibres plus légères, facile à installer et à faible perte de puissance. Il reste cependant à évaluer avec une précision centimétrique les délais réels induits sur chaque signal dans le but de garantir une précision de localisation inférieure au mètre. Cette précision semble en effet représenter un bon compromis entre complexité globale du système de localisation et réponse à un ensemble suffisant de besoins des utilisateurs potentiels. On développe alors une technique d'estimation des délais basée sur la mesure de déphasage (entre deux signaux sinusoïdaux) et une analyse statistique des séries de mesures. Pour finir, on présente quelques résultats de localisation obtenus avec notre système à répélites déployé dans un environnement indoor typique

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Crowfoot, Jeremy M. "Highly substituted benzenes, handshakes, and gold core nanoparticles." abstract, 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3326619.

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Brynolf, Max, and Rohini Sengupta. "Magneto-Plasmonic Gold & Nickel Core-Shell Structures." Thesis, Uppsala universitet, Materialfysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-387353.

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The presented project explores the optical properties of magnetoplasmonic Au/Ni core-shell structures. The work aims at controlling dimensions and parameters in order to influence and analyze the optical properties of the nanostructures. The softwares utilized for the simulations were COMSOL Multiphysics 5.1 and MATLAB. Experimental results were acquired from labs done at Ångströms laboratory. From the research based study where the gold to nickel ratio was influenced, it was observed that the transmissions for the nanostructures at the differing wavelengths produced transmissions of similar bearings. Modes for certain wavelengths were found in correspondence with the transmissions and could potentially render explanations for influence on the optical properties of the nanostructures. Conclusively, it can be stated that the optical properties of the nanostructures could be influenced and controlled by varying the dimensions and properties of the said structure. Differing dimensions corresponded to noteworthy changes in the cross sections, the transmissions as well as the mode formations.

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Garlyyev, Batyr. "Synthesis and catalytic study of shell-shell, core-shell hollow gold nanocatalysts." Diss., Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/54996.

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Metal nanoparticles have a large surface area to volume ratio compared to their bulk counterparts, which makes them attractive to use as catalysts. Atoms on the surface of metal nanoparticles are very active due to their high surface energy resulting from their unsatisfied valency. First synthesis of gold nanoparticles with different shapes and bimetallic structure are explored in detail. Then an experimental method which could distinguish between the two mechanisms (homogeneous or heterogeneous) by using hollow plasmonic gold nanocatalyst is developed. Furthermore the catalytic activity of gold nanocages was changed by adding an inner platinum or palladium nanoshell. Results suggested that adding palladium inner shell increased the activity of gold nanocages towards the reduction nitro groups to amino groups. Controlling the selectivity of the catalyst is an important goal of catalysis research. Lastly selectivity of the plasmonic nanocatalyst (Gold sphere-Gold shell Nanorattles) with multiple plasmon modes was studied for photo-dimerization of nitro groups into azo dimers were studied on gold nanocatalyst surface. Results showed that selectivity can be controlled by changing the wavelength of the light exciting surface plasmon.

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Selmi, Ikhlas. "Optimisation de l'infrastructure d'un système de positionnement indoor à base de transmetteurs GNSS." Electronic Thesis or Diss., Evry, Institut national des télécommunications, 2013. http://www.theses.fr/2013TELE0024.

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Dans le but de fournir un service GNSS (Global Navigation Satellite System) de localisation continu et disponible partout, les systèmes utilisant des pseudolites et des répéteurs semblent être des solutions pertinentes pour la localisation en indoor. Le système à répélites, inspiré de ces deux méthodes (répéteurs et pseudolites), est aussi proposé pour résoudre cette problématique. Les répélites sont des transmetteurs locaux qui, installés en intérieur, formeront une constellation locale. Ils émettent tous un signal GNSS unique mais déphasé par un délai spécifique à chacun d’eux. Ces délais sont nécessaires pour distinguer les différents signaux reçus au niveau du récepteur. Les travaux de cette thèses sont réalisés dans le cadre du système à répélites et dans l’objectif d’améliorer son architecture et de réduire ses interférences inter-système. En effet, l’architecture du système (un peu encombrante) et les interférences éventuelles avec les signaux satellitaires reçus par un récepteur placé à l’extérieur font partie des inconvénients de ce système. On cherche donc à traiter ces deux difficultés de façon à minimiser leurs effets. Dans une première partie, on étudie les différents codes GNSS existants dans la littérature ainsi que les techniques de modulation employées. Ceci nous mène à proposer des codes ayant un niveau d’interférence équivalent à la référence GPS (obtenue entre deux codes GPS) pour les bandes L1 de GPS et G1 de Glonass. Dans une seconde étape, on développe la modulation IMBOC (Indoor Modified Binary Offset Carrier) pour générer de nouveaux codes caractérisés par des niveaux d’interférence réduits (comparés à la référence GPS). Parmi ces codes il y a deux catégories : ceux qui sont adaptés aux systèmes à répélites (émettant un code unique) et ceux qui sont adaptés aux systèmes pseudolites. Une étude théorique et des simulations des niveaux d’interférences pour les codes émis dans la bande GPS et Glonass sont réalisées pour déterminer les gains en termes de niveaux de bruit. Ce gain (par rapport à la référence GPS) en puissance d’interférence s’élève à 16 dB pour Glonass et 20 dB pour GPS. Pour valider les performances de ces codes, on génère les signaux IMBOC et on observe les interférences réelles qu’ils induisent sur un récepteur GPS recevant un signal satellitaire. Dans la deuxième partie, on utilise la fibre optique pour transmettre le signal du générateur jusqu’aux répélites et pour créer les délais initiaux par propagation du signal dans des bobines de fibre. Ainsi on remplace les câbles coaxiaux et les montages électroniques (de déphasage) par des bobines de fibres plus légères, facile à installer et à faible perte de puissance. Il reste cependant à évaluer avec une précision centimétrique les délais réels induits sur chaque signal dans le but de garantir une précision de localisation inférieure au mètre. Cette précision semble en effet représenter un bon compromis entre complexité globale du système de localisation et réponse à un ensemble suffisant de besoins des utilisateurs potentiels. On développe alors une technique d’estimation des délais basée sur la mesure de déphasage (entre deux signaux sinusoïdaux) et une analyse statistique des séries de mesures. Pour finir, on présente quelques résultats de localisation obtenus avec notre système à répélites déployé dans un environnement indoor typique
In order to make the GNSS positioning service continuous and available when going from an outdoor to an indoor environment, pseudolite and repeater based systems have been developed. A new system called repealite is a combination of both pseudolites and repeaters. It is based on transmitting a single signal through a set of transmitters (thus creating the local constellation). In order to avoid interference between the repealite signals and to distinguish between them at the receiver’s end, each signal is shifted with a specific delay. The research carried out in this PhD aims at optimizing two aspects of the repealite based system. Firstly, we need to mitigate the effect of the interference caused on the satellite signals received outdoors. So we decided to design new codes characterized by low interference levels with outdoor signals. Secondly, we worked on the infrastructure part in order to simplify it and to make it easier to install: this is mainly achieved through the use of optical fibers. In the first part, we study the codes and the modulation techniques currently used in the GNSS systems. Then, we propose a few codes having an interference level equivalent to that of the GPS (obtained when computing two GPS codes). These new codes are compatible with the GPS L1 or the Glonass G1 bands. In a second step, we focus on the modulation techniques and create the so-called IMBOC (Indoor Modified Binary Offset Carrier) that aims at minimizing the interference levels with outdoor signals. With this modulation, we propose new IMBOC codes capable of much lower interference levels than the GPS reference. In order to evaluate the performance of the proposed codes, we carried out a theoretical study, simulations and experimental tests. The interference gain reached about 20 dB on the GPS band and 16 dB on the Glonass one. The proposed codes are divided into two categories: those reserved to the repealite system (using a single code) and families of codes suited to pseudolite–based systems. Finally, we generated the IMBOC signals modulated by the new codes and tested the real interference induced on an outdoor receiver tracking the satellite signals. In the second part, we use optical fibers in order to replace the coaxial cables used to transmit signals from the GNSS-like signal generator to the repealites. In addition, the initial delay needed for each repealite is added by propagating the signals through rolls of fibers. Indeed, optical fiber offers advantages such as lightness, flexibility and low power loss that make it suitable to simplify the infrastructure of the system. In order to evaluate the real delays of these various fibers, we develop an estimating method based on phase shift measurements (between two sinusoidal signals) and statistical analysis of the series of measurements. This method should have uncertainties lower than one centimeter in order to insure a sub-meter precision (in absolute positioning with the repealite positioning system). In order to validate this method, we compare it to a GNSS based calibration approach. Finally, we carry out a few positioning tests with the repealite positioning system deployed in a typical indoor environment. These tests deal with absolute and relative positioning and give an idea about the system’s performance

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Bush, Melanie E. L. "Breaking the code of good intentions : everyday forms of whiteness." Ann Arbor, Mich. : ProQuest Information and Learning, 2005. http://gateway.proquest.com/openurl?res_dat=xri:ssbe&url_ver=Z39.88-2004&rft_dat=xri:ssbe:ft:keyresource:Sweet_Diss_05.

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Sholanbayeva, Zhanar. "Synthesis, Functionalization And Characterization Of Gold Nanoparticles." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12615069/index.pdf.

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Metallic nanoparticles (NPs) with various elemental composition, size, shape and physical or chemical properties has become active field of research. Among all the metal NPs noble metal ones are receiving much attention due to their special optical properties which make them useful for different applications. Noble metal NPs have bright colors resulting from strong surface plasmon resonance absorption usually in the visible region. The colors are size and shape dependent and provide the tuning of optical properties. The optical properties of NPs are also strongly depending on the nature of the NPs surface which plays a crucial role on chemical sensing. Therefore, surface modification of NPs has become increasingly important. In this study, gold NPs were prepared in aqueous phase by seed-mediated growth method. To enhance the optical properties, surface functionalization was performed by coating NPs with silver. The coating process was achieved by chemical reduction of silver ions on NPs surface. Thickness of silver layer on the NPs were attempted to be controlled by the amount of silver salt added into NPs solution. Coating process of different types of gold NPs (rod, octahedral, star) was done by the same procedure. Moreover, this attempt yielded control over silver layer thickness on sphere, rod and octahedral shaped gold NPs, but not on branched NPs. The structure, composition and spectroscopic properties of Au-Ag core shell NPs were characterized by UV-Vis spectroscopy, Field Emission Transmission Electron Microscope (FE-TEM) and Energy-dispersive X-ray (EDX) studies, Scanning Electron Microscope (SEM), and X-Ray Photoelectron Spectroscopy (XPS). The analysis showed that all NPs studied were successfully coated with silver and promising for further explorations in sensing and imaging applications.

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Ban, Zhihui. "The Synthesis of Core-Shell Iron@Gold Nanoparticles and Their Characterization." ScholarWorks@UNO, 2004. http://scholarworks.uno.edu/td/83.

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Au-coated magnetic Fe nanoparticles have been successfully synthesized by partial replacement reaction in a polar aprotic solvent with about 11 nm core of Fe and about 2.5 nm shell of Au. In this work, a combination of TEM (transmission electron microscopy), XRD (X-ray Powder Diffractometry), EDS (Energy disperse X-ray spectroscopy), SQUID (Superconducting Quantum Interference Device), TGA (Thermograviometric analysis), UV-visible absorption spectroscopy and Faraday rotation were employed to characterize the morphology, structure, composition and magnetic properties of the products. HRTEM images show clear core-shell structure with different crystal lattices from Fe and Au. SQUID magnetometry reveals that particle magnetic properties are not significantly affected by the overlayer of a moderately thick Au shell. The Au-coated particles exhibit a surface plasmon resonance peak that red-shifts from 520 to 680 nm. And all the above characterizations show that in this sample, there are no Fe oxides inside the particle.

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Martini, Matteo. "Synthesis and optical properties of fluorescein encapsulated in gold (core) / silica (shell) architectures : how gold renders particles brighter." Lyon, INSA, 2008. http://theses.insa-lyon.fr/publication/2009ISAL0035/these.pdf.

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The thesis concerns the development and the characterization of silica nanostructures containing at the same time organic fluorophores and gold clusters. Precisely, we prepared core-shell architectures (core=gold, shell=silica) by using the sol-gel method. In the first part of work which describes the particle synthesis, we showed that the technique of microemulsion allowed the simultaneous encapsulation of organic molecules and metal nano-objects in silica beads. In particular, we showed by transmission electron microscopy that the preliminary formation of gold core inside micelles had a structuring effect on the silica shells, conferring to the final structure a strict control of the size, homogeneity and morphology. In the second part of this work, we confirmed that such kind of nano-objects presented new unusual optical properties. Indeed, whenever we can increase the luminescence of an object by the simple incorporation of larger quantities of organic fluorophores we income into the limitation generated by the “self-quenching”. In order to elucidate this phenomenon, we systematically studied the optical properties of these architectures by fluorescence measurements (to determine the quantum yield of entrapped fluorescein molecules) and the time resolved measurements (to determine the lifetime constant of dyes). We concluded that, contrarily to the literature predictions, the presence of gold particles (i) modified not much the radiative rate of the fluorophores but, on the other hand, (ii) dramatically decreased their non-radiative rates. To explain better this last phenomenon, we measured the energy transfer rates by steady-state and time-resolved anisotropy measurements. The results show that, if the presence of gold accelerates significantly the transfer rate, those are also done in a more selective way. The transfers of excitation towards organic dimers (that act as fluorescence traps) decrease dramatically and subsequently the samples containing gold nanoparticles display the quasi-suppression of the “self-quenching”. The results obtained in this thesis open the way towards the development of more powerful probes in the fields of the bio-detection and the fluorescence imaging
Le sujet de la thèse concerne l'élaboration et la caractérisation de nanostructures de silice contenant à la fois des fluorophores organiques et des nanoparticules d'or. Précisément, il s’agit d’architectures de type cœur – coquille (cœur=or, coquille=silice) préparées en utilisant les méthodes de la chimie sol-gel. Dans la première partie du travail consacrée à l’élaboration, nous avons démontré que la technique de microémulsion permettait l’encapsulation simultanée de molécules organiques et de nano-objets métalliques dans des billes de silice. En particulier, nous avons montré par microscopie électronique à transmission que la formation préliminaire d’un cœur d’or à l’intérieur des micelles avait un effet structurant sur les coquilles de silice, conférant aux architectures finales un strict contrôle de la taille, de l’homogénéité et de la morphologie. Dans la seconde partie de ce travail, nous avons apporté la preuve que les objets ainsi réalisés présentaient des propriétés optiques inédites. En effet, on peut en augmenter la luminescence par simple incorporation de quantités grandissantes de fluorophores organiques sans se heurter à la limitation habituelle générée par le « quenching de concentration ». Dans le but d’élucider ce phénomène, nous avons étudié systématiquement les propriétés optiques de ces architectures par des mesures de fluorescence (pour en déterminer le rendement quantique) et en temps résolu (pour en déterminer la durée de vie). Nous avons conclu que, contrairement aux prédictions de la littérature, la présence de particules d’or ne modifiait que très peu la vitesse de désexcitation radiative des fluorophores mais, en revanche, en diminuait de manière nette celle de désexcitation non radiative. Pour parfaire la compréhension de ce dernier phénomène, nous avons mesuré les vitesses de transfert d'énergie entre fluorophores par des mesures d'anisotropie stationnaire et dépendante du temps. Ces mesures montrent que, si la présence d’or accélère d’un facteur significatif la vitesse de transfert, ceux-ci se font aussi de manière plus sélective. Les transferts d’excitation vers les dimères organiques (se comportant comme des puits de fluorescence) deviennent alors très peu probables, ce qui permet d’expliquer finalement la quasi-suppression du « quenching de concentration ». Les résultats obtenus dans cette thèse ouvrent la voie au développement de sondes plus performantes dans les domaines de la bio-détection et de l’imagerie de fluorescence

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19

Sallaway, Peter J. (Peter James). "Asymptotically good convolutional codes with feedback encoders." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42787.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.
Includes bibliographical references (leaves 47-49).
by Peter J. Sallaway.
M.Eng.

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20

Roemer, Ryan Glenn. "Finding the bad in good code automated return-oriented programming exploit discovery /." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p1464668.

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21

El, Khoury Jouliana M. "Development of Nanostructured Core-Shell Materials for Sensing of Sugars in Vivo." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1123637252.

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22

Wu, Ya-Na. "The assessment of iron core-gold shell nanoparticles in oral and colorectal cancer." Thesis, The University of Sydney, 2011. https://hdl.handle.net/2123/29284.

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Cancer metastasis is the major course of clinical failure. Molecular and cellular mechanisms underlying the pathological process, however, are still not fully elucidated. Nanoparticles based cancer therapy has in recent years attracted significant interest as a potential novel therapeutic means. Especially, metal based nanoparticles-such as, iron or zinc-based particles-have been postulated to possess effective anti-cancer properties. However, detailed information regarding their biodistribution, biocompability, metabolic conversion, subcellular cytotoxic targets, and clearance within normal healthy and cancer cells is lacking and need further investigation (Chapter 1 ). This thesis endeavours therefore to address these issues through the use of advanced molecular cell biology techniques and high-resolution cellular imaging tools. More specifically, in this work, the effectiveness of iron core-gold shell (Fe@Au) nanoparticles was assessed on their ability to kill oral and colorectal cancer cells. Firstly, we were able to demonstrate that Fe@Au nanoparticles selectively and significantly inhibit proliferation of oral- and colorectal-cancer cells while having little adverse effect on normal healthy control cells (Chapter 2). Next, we determined that Fe@Au nanoparticles cause an irreversible membrane potential loss in the mitochondria of cancer cells, but only a transitory decrease in membrane potential in healthy control cells. We also found that the strong cytotoxic effect of Fe@Au nanoparticles in oral cancer cells was a result of mitochondria-mediated autophagy. In this part of the study, we could also demonstrate that some CRC cell lines were found to be less sensitive to the nanoparticle treatment (Chapter 3). In a third major part of our experimental studies we demonstrated that the moderate cytotoxic effect of Fe@Au nanoparticles in CRC was due by the insensitivity to Fe only treatment (Chapter 4). Finally, during the course of experimentation we observed some variability in cytotoxic response among different batches of synthesised Fe@Au nanoparticles. This sparked our interest to optimise the conditions of synthesis, composition and storage of these particles to warrant maximal efficacy for future clinical applications (Chapter 5).

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Doohan, Kim Elizabeth. ""Making things come good" Aborigines and miners at Argyle /." Doctoral thesis, Australia : Macquarie University, 2007. http://hdl.handle.net/1959.14/145.

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Thesis (PhD) -- Macquarie University, Division of Environmental and Life Sciences, Department of Human Geography, 2007.
"November 2006".
Bibliography: p. 352-398.
Mode of access: World Wide Web.
xvi, 399 p. ill., maps

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24

Agoston, Roland M. "Magnetic core/gold shell nanoparticle immunoassay for rapid detection of biomolecules using Raman spectroscopy." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/97978/4/Roland_Agoston_Thesis.pdf.

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Nanomaterials were adorned with recognition molecules and combined with surface-enhanced Raman scattering to selectively separate, identify, and quantify trace amounts of bioactive molecules from within a complex mixture. This work is presented as a rapid, portable, and cost-effective method that complements existing biomolecule analysis techniques, with potential in-field applications in clinical diagnostics, environmental monitoring, and forensic science.

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25

Higgs, Matthew. "The construction of variable length codes with good synchronisation properties." Thesis, University of South Wales, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441217.

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26

Keser, Sezen Lutfiye. "Preparation Of Gold Decorated Cobalt-silica Core-shell Nanoparticles For Surface Enhanced Raman Scattering Applications." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612383/index.pdf.

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Bringing together several materials into a single nanoparticle is an attractive way to design systems that exhibit diverse physical and chemical properties. Cobalt nanoparticles are extensively used in magnetic separation, ferrofluids, and magnetic storage media. The deposition of gold nanoparticles onto cobalt core significantly affects their optical properties due to the introduction of surface Plasmon. Here the synthesis of gold nanoparticles decorated cobalt-silica nanoparticles are reported for the first time. Their optical and magnetic properties and capacity as a surface enhanced Raman scattering (SERS) substrate were investigated. This nano-material is of particular interest as a dual agent allowing both magnetic separation and SERS detection. The synthesis involves three steps: i) synthesis of Co nanoparticles
ii) deposition of a silica shell around the Co core and introduction of amine functional groups on the surface
iii) decoration of the surface with gold nanoparticles. Co nanoparticles were prepared in an inert atmosphere in the presence of capping and reducing agents. Size of the cobalt nanoparticles was varied by changing the concentration of the capping agent. Since cobalt particles are easily oxidized, they were coated with silica shell both to prevent oxidation and allow further functionalization. Silica coating of the particles were performed in water/ethanolic solution of tetraethyl orthosilicate (TEOS). Thickness of silica coating was controlled by varying the concentrations of TEOS. Besides, by adding 3-aminopropyl-triethoxysilane (APTS) to the reaction medium, primarily amine groups were introduced on the silica surface. For further modifications citrate stabilized gold nanoparticles were appended onto the surface of amine modified core-shell cobalt-silica nanoparticles. Gold decorated magnetic core-shell structures were used as SERS substrate with Raman dyes
brilliant cresyl blue (BCB) and rhodamine 6G (R6G). They were also utilized for preconcentration and SERS detection of 4-mercapto benzoic acid (4-MBA). Gold nanoparticles on the silica and thiol group on the 4-MBA were very selective to each other, thus, 4-MBA could be attached on to gold surface and it could be easily separated magnetically from the reaction medium and identified by Raman spectroscopy. Characterization of the cobalt, cobalt-silica and gold modified cobalt-silica nanoparticles was done by Field Emission Scanning Electron Microscopy (FE-SEM), Scanning-Transmission Electron Microscopy (S-TEM), Energy-Dispersive X-ray Spectroscopy (EDX), UV-Vis spectrometry, and Raman microscope system.

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27

Pacanovsky, Aaron James. "Petrology of Gold Ore-Bearing Carbonates of the Helen Zone, Cove Deposit, Lander County, Nevada." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1398682471.

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Scarsella, Thomas M. "An investigation of the potential mobility of gold ions in core/shell silver bromide emulsions /." Online version of thesis, 1991. http://hdl.handle.net/1850/11293.

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Garcia, Soto Mariano de Jesús. "Synthesis of Gold Nanostructures with Optical Properties within the Near-Infrared Window for Biomedical Applications." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/321533.

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The work reported in this dissertation describes the design and synthesis of different gold nanoshells with strong absorption coefficients at the near-infrared region (NIR) of the spectrum, and includes preliminary studies of their use for the photo-induced heating of pancreatic cancer cells and ex vivo tissues. As the emphasis was on gold nanoshells with maximum extinctions located at 800 nm, the methods explored for their synthesis led us to the preparation of silica-core and hollow gold nanoshells of improved stability, with maximum extinctions at or beyond the targeted within the near-infrared window. The synthesis of silica-core gold nanoshells was investigated first given its relevance as one of the pioneering methods to produce gold nanostructures with strong absorption and scattering coefficients in the visible and the near-infrared regions of the spectrum. By using a classical method of synthesis, we explored the aging of the precursor materials and the effect of using higher concentrations than the customary for the reduction of gold during the shell growth. We found that the aging for one week of the as-prepared or purified precursors, namely, the gold cluster suspensions, and the seeded silica particles, along with higher concentrations of gold in the plating solution, produced fully coated nanoshells of 120 nm in size with smooth surfaces and maximum extinctions around 800 nm. Additional work carried out to reduce the time and steps in the synthesis of silica-core gold nanoshells, led us to improve the seeding step by increasing the ionic strength of the cluster suspension, and also to explore the growth of gold on tin-seeded silica nanoparticles. The synthesis of hollow gold nanoshells (HGS) of with maximum extinctions at the NIR via the galvanic replacement of silver nanoparticles for gold in solution was explored next. A first method explored led us to obtain HGS with maximum extinctions between 650 and 800 nm and sizes between 30 and 80 nm from silver nanoparticles, which were grown by the addition of silver nitrate and a mild reducer. We developed a second method that led us to obtain HGS with maximum extinctions between 750 and 950 nm by adjusting the pH of the precursor solution of the silver particles without much effort or additional steps. The last part of this work consisted in demonstrating the photo-induced heating of two biological systems containing HGS. Photothermal therapy studies of immobilized PANC1 pancreas cancer cells in well-plates were carried out with functionalized HGS. We found that cells exposed to HGS remained viable after incubation. Moreover, the cells incubated with HGS modified with mercaptoundecanoic acid and folic acid turned non-viable after being irradiated with a laser at 800 nm. The other study consisted in the laser-induced heating between 750 and 1000 nm of ex vivo tissues of chicken and pork with nanoshells injected. In comparison with non-injected tissues, it was found that the temperature at the irradiated areas with HGS increased more than 10 °C. Moreover, the extent of the heated area was broader when the laser was used at wavelengths beyond 900 nm, suggesting that the heating was due to the radiation absorbed and transformed into heat primarily by the HGS and at a lesser extent by the water in the tissue.

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Sow, Boubacar. "Development of the Domino Pericyclic Oxy-Cope/Ene /Claisen /Diels-Alder Reaction and the Synthesis of Complex Bicyclo[3.3.1]alkenones." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/30344.

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This thesis is a dissertation to support the development of new domino pericyclic oxy-Cope/ene/Claisen/Diels-Alder reaction, diversity oriented synthesis of PPAPs scaffold via sequential one pot cascade reaction and ethyl aluminum sesquichloride catalyzed highly hindered Diels-Alder reaction. The first part concentrates on the domino pericyclic oxy-Cope/ene/Claisen/Diels-Alder reaction. As a result of this study, we have developed a general methodology for rapidly constructing complex diterpenes and discovered a thermal oxy-Cope/ene/Claisen/Claisen rearrangement, applied to the synthesis of trans decalin benzofurans. The second part involved the development of an efficient synthetic approach towards bicyclo[3.3.1]nonenone core found in many natural products, via a sequential Diels-Alder/gold(I)-catalyzed 6-endo-dig cyclization and its application to the synthesis of a diversified library of PPAPs. Finally, we have developed an efficient synthetic methodology for the formation of cyclohexene rings bearing quaternary carbon centers via an ethyl aluminum sesquichloride mediated highly hindered Diels-Alder reaction. This method solved an important problem encountered in the synthesis of many natural products including PPAPs. This methodology opened new opportunities in the total synthesis of PPAPs.

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Hain, Jessica. "Funktionalisierte Polymerkomposite auf Basis von Poly(3,4-ethylendioxythiophen) und Gold." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1209477679749-98205.

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Poly(3,4-ethylenedioxythiophene), PEDOT, belongs to the group of conducting polymers and is characterized by its high stability, a moderate band gap and its optical transparency in the conductive state. A large disadvantage of conducting polymers, and also PEDOT, is their poor solubility. One way to achieve processible materials is the synthesis of colloidal particles. Thus, this work focuses on the development of conductive particles by preparing composite structures. Polymeric colloids like latex particles and microgels were used as templates for the oxidative polymerization of EDOT. Depending on template structure completely different composite morphologies with variable properties were obtained. It was found that modification with PEDOT did not only cause conductive particles for application as humidity sensor materials, but also candidates for further functionalization with gold nanoparticles (Au-NPs). Due to a multi-stage synthesis route it was possible to achieve polystyrene(core)-PEDOT(shell)-particles decored with Au-NPs. Microgels acting as “micro reactors” for the incorporation of PEDOT and Au-NPs were also used for preparing multifunctional composites for catalytic applications
Poly(3,4-ethylendioxythiophen), PEDOT, gehört zur Gruppe der leitfähigen Polymere und zeichnet sich durch seine hohe Stabilität, eine moderate Bandlücke und seine optische Transparenz im dotierten Zustand aus. Ein Nachteil leitfähiger Polymere, wie auch von PEDOT, ist deren schlechte Löslichkeit. Die Synthese kolloidaler Partikel bietet jedoch eine Möglichkeit dieses Problem zu umgehen. In diesem Zusammenhang richtete sich der Fokus dieser Arbeit auf die Darstellung leitfähiger Partikel in Form von Kompositstrukturen. Polymerkolloide, wie Latex- und Mikrogelpartikel, sind als Template eingesetzt worden, in deren Gegenwart PEDOT durch eine oxidative Polymerisation synthetisiert wurde. In Abhängigkeit von der Struktur des Templats sind unterschiedliche Kompositmorphologien mit steuerbaren Eigenschaften erhalten worden. Auf diese Weise wurden neben Materialien für die Feuchtigkeitssensorik leitfähige Kompositpartikel hergestellt, die zusätzlich mit Gold-Nanopartikeln (Au-NP) funktionalisiert werden konnten. Durch ein mehrstufiges Syntheseverfahren sind somit Polystyrol(Kern)-PEDOT(Schale)-Partikel mit Au-NP-funktionalisierter Oberfläche synthetisiert worden. Mikrogelpartikel, die als „Mikroreaktoren“ für die Inkorporation von PEDOT- und Au-NP dienten, wurden ebenfalls eingesetzt, um multifunktionale Komposite mit katalytischen Eigenschaften herzustellen

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Rondina, Mattia. "Studio di validità concorrente tra sistema indossabile basato su IMU e stereofotogrammetria usata come gold standard." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8641/.

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L’analisi della postura e del movimento umano costituiscono un settore biomedico in forte espansione e di grande interesse dal punto di vista clinico. La valutazione delle caratteristiche della postura e del movimento, nonché delle loro variazioni rispetto ad una situazione di normalità, possono essere di enorme utilità in campo clinico per la diagnosi di particolari patologie, così come per la pianificazione ed il controllo di specifici trattamenti riabilitativi. In particolare è utile una valutazione quantitativa della postura e del movimento che può essere effettuata solo utilizzando metodologie e tecnologie ‘ad hoc’. Negli ultimi anni la diffusione di sensori MEMS e lo sviluppo di algoritmi di sensor fusion hanno portato questi dispositivi ad entrare nel mondo della Motion Capture. Queste piattaforme multi-sensore, comunemente chiamate IMU (Inertial Measurement Unit), possono rappresentare l’elemento base di una rete sensoriale per il monitoraggio del movimento umano.

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Yontz, Nicholas Allen. "Determining the Correlation Between Core Performance and Golf Swing Kinematics and Kinetics." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1281540237.

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34

Benin, Bogdan Markovich. "Synthesis and Characterization of Novel Gold-Based Nanoparticulate Chemotherapeutic Agents." Kent State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=kent1461088605.

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35

Deol, Suprit S. "Stability, cytotoxicity, and cell permeability of dendron-conjugated gold nanoparticles with 3, 12, and 17 nm core." Thesis, California State University, Long Beach, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1590079.

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This thesis describes the synthesis of water-soluble dendron-conjugated gold nanoparticles (Den-AuNPs) with various average core sizes and the evaluation of stability, cytotoxicity, and cell permeability and uptake of these materials. The characterization of Den-AuNPs using various instruments including transmission electron microscopy (TEM), matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF-MS), 1H NMR, FT-IR, and UV-vis spectroscopy confirms the dendron conjugation to the glutathione-capped gold nanoparticles (AuNPs). The stability of AuNPs and Den-AuNPs in solutions of different pH and salt concentration was determined by monitoring changes in surface plasmon bands of gold using UV-vis spectroscopy. The Den-AuNPs were found to be more stable than the precursor AuNPs maintaining their solubility at the pHs higher than 4 and with the salt concentrations of up to 100 mM. The improved stability of Den-AuNPs suggests that the post-functionalization of thiol-capped gold nanoparticle surfaces with dondrons can further improve the physiological stability and biocompatibility of gold nanoparticle-based materials. Cytotoxicity studies with AuNPs and Den-AuNPs with and without flourophores were also performed by examining cell viability for 3T3 fibroblasts using a MTT cell proliferation assay. The conjugation of dendrons to the AuNPs with flourophores was able to decrease the cytotoxicity brought about by the flourophores. The successful uptake of Den-AuNPs in mouse fibroblast 3T3 cells shows the physiological viability of the hybrid materials.

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36

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1263899.

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Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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37

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1265279.

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Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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38

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1263921.

Full text

Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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39

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1251268.

Full text

Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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40

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1264041.

Full text

Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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41

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1263959.

Full text

Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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42

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1265359.

Full text

Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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43

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1266684.

Full text

Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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44

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1265259.

Full text

Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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45

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1251349.

Full text

Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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46

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1263981.

Full text

Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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47

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1264019.

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Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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48

NICOLINI, CORRADO. "Gold(I)-catalyzed intramolecular enantioselective hydroalkoxylation reaction for the total synthesis of metabolites containing the tetrahydrofuran core." Doctoral thesis, Università degli studi di Pavia, 2019. http://hdl.handle.net/11571/1251309.

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Abstract:

Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.
Several natural products and biologically active compounds present oxygenated five- membered rings as structural motif. In particular, substituted tetrahydrofurans are commonly occurring building blocks found both within terrestrial and marine metabolites. These substances exhibit a wide range of biological activities such as anti-microbial, anti- tumoral, anthelmintic, anti-malarial and anti-protozoal. As such, over the last decades, considerable efforts have been devoted towards the development of efficient and completely stereoselective strategies for the construction of substituted THF rings. Many efforts indeed in this thesis have been devoted to the development of a new synthetic methodology to access such building block, exploiting a versatile and efficient gold(I) catalysis. In particular, this thesis reports the first example of accelerative asymmetric gold(I) catalysis via chiral ligand metal cooperation. An asymmetrically positioned remote amide group in the 3’ position of the designed gold(I) chiral binaphtyl ligand enables a selective acceleration of the cyclization reaction of allenyl substrates into one prochiral allene face through general base catalysis, achieved by H-bonding with the incoming nucleophlic hydroxyl group. Owing to the accelerative nature of the catalysis, a high level of efficiency and selectivity can be accessed, which is proved thanks to exceptional ee values and extremely low catalyst loading, as low as 100 ppm. This type of catalytic scenario demonstrates to be of wide applicability. Firstly, attention has been drawn towards 4-allen-1-ols, which can undergo the gold(I) cyclization reaction smoothly in feasible conditions with almost quantitative yields and very high ee values, both with achiral and chiral substrates; in the latter case the reaction remains highly efficient and most importantly maintains excellent allene facial selectivities regardless of the substrate stereochemistry. Moreover, many functional groups are well tolerated. Secondly, the attention has been driven towards Medius, which undergoes cyclization reaction affording disubstituted THF systems in high yields and exceptionally high ee values exploiting the same type of approach above described. The employment of classical approaches such as Toste’s or Widenhoefer’s or Mikami’s does not afford high ee or dr values, despite excellent yields. On the other hand, moderate dr values are obtained as a consequence of poor control of the catalyst over the prochiral center present in the substrate, as can be expected. Nevertheless, extremely high ee values are ensured by the great allene facial selectivity attack by the nucleophile. Moreover, the absolute as well as the relative configurations of the stereogenic centers present in the product of the cyclization of Medius have been determined, proving that the cis product is preferred over the trans one. In the third place, a complete methodological work on the gold(I) cyclization reaction of Remotus has been also carried out. Even in this case, like in Medius’ one, quantitative yields and very high ee values can be obtained through Zhang’s catalyst. However, as expected, very poor dr values can be accessed as a consequence of the nature of the substrate. To sum up, this thesis proves that gold(I) catalysis, in particular in the case of gold(I) ligand accelerative catalysis, represents a powerful tool in organic synthesis to enantioselectively build variably substituted THF systems in almost quantitative yields, exceptionally high ee values, and good dr values, using an extremely low catalyst loading thanks to the efficiency of the catalysis.

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49

Rosenbaum, Deborah Ilse. "What's good for the gander is good for the goose helping cancer patients to cope by treating their spouses /." Diss., Online access via UMI:, 2006.

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Parrott, Deborah, and Reneé C. Lyons. "Uncommonly Good: Public Librarians and School Librarians Working Together For Common Core." Digital Commons @ East Tennessee State University, 2016. https://dc.etsu.edu/etsu-works/2373.

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What do public librarians and school librarians have in common? We all want to serve our patrons as well as contribute to literacy and higher reading rates within our communities. Since the adoption of Common Core Standards in many states, users have called on librarians for assistance with information, resources and knowledge relating to these standards. Public librarians and school librarians can effectively collaborate to help each other reach their goals of user satisfaction and increased reading. Join this session to discover the fundamentals of Common Core and how we can help.

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Dissertations / Theses on the topic 'Code de Gold'

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