Dissertations / Theses on the topic 'Reactif grignard'

Une methode generale de synthese stereospecifique de motifs dieniques 1,5- et 1,6- a ete developpee: la reaction de reactifs de grignard actives par des complexes de nickel adequats sur le dihydrofurane et le dihydropyrane, dont la configuration de la double liaison est preetablie. Elle a permis l'acces rapide et stereoselectif (z=99%) a des alcools homo- et bis-homoallyliques z. A partir du dihydrofurane et en repetant la reaction, on peut obtenir des dienes 1,5 et 1,6- a partir du dihydropyrane. Ces resultats ont ete appliques a la preparation a grande echelle de pheromones d'insectes: l'acetate de (6z,11z)-hexadeca-6,11-dien-1-yle, pheromone d'eudia pavonia, et le (5z,9z)-heptacosa-5,9-diene, pheromone de drosophila melanogaster synthetisee pour la premiere fois pour identification. Une nouvelle synthese efficace et peu couteuse du gossyplure, pheromone du ver rose du cotonnier, melange 1:1 d'acetates de (7z,iie)- et de (7z,11z)-hexadeca-7,11-dien-1-yle a ete proposee. Elle a ete realisee a partir d'un melange 1:1 de (3z)- et (3e)-bromo-3-enes obtenu par isomerisation photochimique (decouverte fortuitement) de l'isomere z. Enfin, une autre potentialite de la reaction etudiee a ete mise en valeur. Elle consiste a privilegier la reaction de beta-elimination d'hydrogene sur des reactifs de grignard appropries (bromure d'isopropylmagnesium). A l'aide d'un complexe de nickel monodente, cette reaction effectuee sur des 6-alkyl-3,4-dihydro-2h-pyranes aboutit a des alcools 5-alkyl-bis-homoallyliques (e=95%)

The development of chiral organometallics for asymmetric synthesis is a topic of significant research in the recent past. The most studied in this class are the chiral organolithium reagents with many reported examples. The primary focus of our research is the development of C_α-chiral Grignard reagents, where the metal bearing α-carbon is the sole source of chirality. Examples of such Grignard reagents are rare owing to the problems associated with their synthesis, and their low configurational stability. We have studied these problems in three different modules of this project. Reactions of 1-magnesio-2,2-diphenyl-cyclopropylcarbonitrile with carbon electrophiles are first attempted in order to expand the utility of this configurationally stable C_α-chiral Grignard reagent in asymmetric synthesis. This reagent has been shown to be non-reactive towards carbon electrophiles at low temperatures. Consequently, we attempt to enhance the reactivity of this compound through two different approaches, Lewis-base activation and the "ate-complex" generation. The Magnesium/Halogen (Mg/X) exchange reactions have been shown to be extremely useful in the synthesis of complex Aryl, alkenyl (sp²) and alkynyl (sp) Grignard reagents. Examples of Mg/X exchange reactions of Alkyl (sp³) halides are, however, rare. Even more rare are such examples with secondary and tertiary alkyl halides, justifying the relative paucity of chiral Grignard reagents. In this module of our project, we study the Mg/X exchange reactions on secondary alkyl halides possessing a γ-hydroxyl group, as an internal activator for such Mg/X exchange reactions. Enantiomerization pathways of chiral organolithium compounds have been widely studied. However, few such studies have been performed on chiral Grignard reagents. In this module of the project, we studied the solvent assisted enantiomerization mechanism of the C_α-chiral 1-magnesio-2,2-diphenyl-cyclopropylcarbonitrile. Rate constant for the enantiomerization of this compound was measured in three different ethereal solvents to study the effect of solvent on the configurational stability. Finally, the order of the enantiomerization process with respect to [Et₂O] was studied in order to predict the mechanism of this process in Et₂O solvent. Our kinetic studies on the enantiomerization process provided us with a definitive picture for the enantiomerization of the C_α-chiral 1-magnesio-2,2-diphenyl-cyclopropylcarbonitrile, where solvation of the Grignard reagent preceded an ion-pair separation step which eventually lead to enantiomerization of the Grignard species. However, the precise structure of all the involved solvated intermediates could not be determined as kinetics was not able to distinguish between these intermediates. We next performed computational calculations to study the effect of solvation on the analogous 1-magnesio-cyclopropylcarbonitrile in order to address the unanswered questions from our kinetic studies.
Ph. D.

U disertaciji je ostvarena sineza amida i oksazolina žučnih kiselina, kao i njihovih alkil i alkilidenskih derivata polazeći od holne kiseline. Ipitano je ponašanje različitih okso derivata žučnih kiselina u uslovima Grignard-ove i Wittig-ove reakcije. Ispitana je biološka aktivnost odabranih sintetizovanih jedinjenja
Synhesis of bile acid amide and oxazoline derivatives, and their alkyl and alkylidene derivatives was accomplished starting from cholic acid. Also, chemical behavior of different bile acid oxo derivatives in Grignard and Wittig reaction was investigated. Biological activity  of selected synthesized compounds was evaluated.

Despite the unfavorable pharmacokinetic properties associated with peptides, they are still of great interest in drug development due to a multitude of interesting biological functions. The development of peptidomimetics strives to maintain or improve the biological activity of a peptide concurrently with removing the unwanted properties. This thesis describes two synthetic approaches to peptidomimetics with particular emphasis on secondary structure mimetics. First the design, synthesis and evaluation of two beta-turn mimetics incorporated in the endorphin Leu-enkephalin is presented. The beta-turn mimetics were stabilized by replacement of the intramolecular hydrogen bond with an ethylene bridge, and the amide bond between Tyr and Gly was replaced with an ether linkage. Linear analogues of the two mimetics were also synthesized. The peptidomimetics and their linear analogues were evaluated in a competitive binding assay at two opiate receptors, my and delta. One of the cyclized beta-turn mimetics was found to be a delta receptor antagonist with an IC50 value of 160 nM. Second a synthetic strategy to a beta-strand mimetic using 2-fluoro-4-iodopyridine as scaffold is described. The synthesis involved a Grignard exchange reaction on the pyridine scaffold using an amino acid derivative as electrophile followed by an SNAr reaction using an amine as nucleophile. The synthesis of a tripeptidomimetic of Leu-Gly-Gly and attempts to introduce chiral building blocks at the C-terminal, as well as studies towards elongated mimetics are presented. Two additional studies deal with the synthesis of two classes of potential thrombin inhibitors based on the pyridine scaffold. The first class contain pyridine as central fragment (P2 residue) substituted with a para-amidinobenzylamine group as P1 residue and various benzoyl groups as P3 residues. Three potential thrombin inhibitors were synthesized and found to be microM inhibitors in an enzymatic assay. In the second class, the pyridine ring serves as P3 residue. This class also lacks a strongly basic group in the P1 position. A small library of eight compounds were synthesized and evaluated in the enzymatic assay. Unfortunately, these compounds lacked inhibitory activity.

En chimie organique, le développement de méthodes de synthèse robustes et respectueuses de l’environnement a toujours été un défi. De plus, en chimie médicinale, la mise au point de méthodes de synthèse de synthons fluorés de haute valeur ajoutée sont importantes pour avoir accès à des composés bioactifs. Dans ce manuscrit, nous présentons des méthodes efficaces et faciles à mettre en œuvre pour la formation de liaisons carbone-carbone catalysée par le nickel et la formation de liaisons carbone hétéroatome par un réarrangement de β aminoalcools α-trifluorométhylés.Nous avons montré que le couplage croisé entre un éther d’énol méthylique et un réactif de Grignard pouvait être catalysé par un système simple à base de Ni(OAc)2/(O)PPh3 dans des conditions douces (40°C) via l’insertion du nickel dans la liaison C-OMe. Cette méthode a été appliquée à la synthèse d’un composé antitumoral, le DMU-212.La synthèse d’amines α-trifluorométhylées linéaires énantioenrichies a été réalisée selon une réaction de réarrangement régiosélectif de β-aminoalcools α-trifluorométhylés en se basant sur une stratégie établie dans le laboratoire via un intermédiaire aziridinium. Nous avons montré que les produits obtenus pouvaient être engagés dans des réactions de post-fonctionnalisation
In organic chemistry, the development of robust and sustainable synthetic methods has always been a challenge. Moreover, in medicinal chemistry, the development of fluorinated building blocks synthetic methods with high value is important to access bioactive compounds. In this manuscript, we report efficient and easy to carry methods for the formation of carbon-carbon bonds catalyzed by nickel and the formation of carbon-heteroatom bonds by a rearrangement of α-trifluoromethyl-β aminoalcools.We demonstrated that it is possible to perform a cross-coupling reaction of an alkenyl methy ether with a Grignard reagent using a simple catalytic system based on Ni(OAc)2/(O)PPh3 under mild conditions (40°C) via the insertion of nickel into C-OMe bond. This method has been applied to the synthesis of an antitumoral agent, DMU-212.The synthesis of enantioenriched linear α-trifluoromethylamine derivatives is reported consisting in a rearrangement of α-trifluoromethyl-β aminoalcool based on an established strategy in our group via an aziridinium intermediate. We have shown that the synthesized compounds can be involved in post-functionalization reactions

En esta memoria se describe la síntesis de N-(terc-butilsulfinil)iminas promovida por microondas, así como su aplicación a la preparación de diferentes heterociclos nitrogenados ópticamente enriquecidos por adición diastereoselectiva de reactivos organozíncicos. Esta memoria ha sido dividida en los siguientes capítulos: Capítulo I: Síntesis de N-(terc-Butilsulfinil)iminas promovida por microondas. En este capítulo se describe la síntesis de diferentes aldiminas y cetiminas por condensación del correspondiente aldehído o cetona con 2-metilpropano-2-sulfinamida en ausencia de disolvente y promovida por microondas. Capítulo II: Síntesis de N-heterociclos. En este capítulo se ha llevado a cabo la preparación de heterociclos nitrogenados de diferentes tamaños a partir de los productos generados por adición diastereoselectiva de triorganozincatos con sustituyentes insaturados a las iminas obtenidas en el capítulo I.

U radu je ostvarena enantiodivergentna totalna sinteza oba enantiomera goniofufurona, 7-epi-goniofufurona i krasalaktona C polazeći iz D-glukoze. Ključne faze u sintezi 7-epi-(+)-goniofufurona bile su stereoselektivna adicija fenilmagnezijum bromida na aldehidnu grupu pogodno zaštićene dialdoze, i stereospecifično formiranje furano-laktonskog prstena ciklokondenzacijom odabranog hemiacetalnog derivata sa Meldrum-ovom kiselinom. Sinteza (+)-goniofufurona i (+)-krasalaktona C zahtevala je inverziju konfiguracije na C-5u zajedničkom intermedijeru, koja je efikasno ostvarena u uslovima Mitsunobu-ove reakcije, ili alternativno oksidacijom benzilne hidroksilne grupe u prohiralni keton, uz naknadnu stereoselektivnu redukcijom sa borohidridom. Sličan pristup je zatim primenjen za sintezu neprirodnih (−)-enantiomera goniofufurona, 7-epi-goniofufurona i krasalaktona C, dva nova konformaciono ograničena analoga (+)- i (−)-goniofufurona (oksetani 36 i ent-36), kao i odgovarajućih 7-deoksigenovanih derivata (31 i ent-31). Takodje je razvijena i prva totalna sinteza prirodnog (+)-krasalaktona B (3) i alternativna sinteza (+)-krasalaktona C (4) polazeći iz D-glukoze. Selektivni pristup molekulima 3, odnosno 4 omogućen je promenom uslova za TBDPS deprotekciju u finalnom intermedijeru 53. Osnovna karakteristika pomenutih pristupa je njihova generalnost i fleksibilnost. Na taj način je omogućena sinteza serije analoga i derivata (+)-goniofufurona, ili 7-epi-goniofufurona, uključujući i do sada nepoznate 7-epi-(+)-krasalaktone B (6) i C (7), 5,7-di-O-cinamoil derivate 8 i 9, 5,7-di-O-izopropilidenske derivate 5 i 10, kao i više lipofilnih derivata (jedinjenja 26, 30, 33, 65, ent-30 i ent-33). Konačno, u drugom delu rada, ispitan je uticaj sintetizovanih stiril-laktona na rast odabranih tumorskih ćelijskih linija in vitro.
Enantiodivergent total syntheses of both (+)- and (−)-enantiomers of goniofufurone, 7-epi-goniofufurone and crassalactone C have been accomplished starting from D-glucose. The key steps of the synthe-sis of 7-epi-(+)-goniofufurone were a stereo-selective addition of  phenyl magnesium bromide to a protected dialdose, followed by a stereospecific furano-lactone ring formation by condensation of a partially protected lactole with Meldrum’s acid. The synthesis of (+)-goniofufurone and (+)-crassalactone C required a configurational inversion at C-5 in the common intermediate that was efficiently achieved under the standard Mitsunobu conditions, or alternatively through a sequential oxidation of the benzylic hydroxyl group followed by a stereo-selective reduction with borohydride. A similar approach was applied to the synthesis of the unnatural enantiomers of goniofufurone, 7-epi-goniofufurone and crassalactone C, two novel, conformationally constrained analogues of both (+)- and (−)-goniofufurone (oxetanes 34 and ent-34). as well as the corresponding 7-deoxygenated derivatives (31 and ent-31). We have also developed the first total synthesis of (+)-crassalactone B (2) and an alternative synthesis of (+)-crassalactone C (3) starting from D-glucose. Finally, the synthesized styryl-lactones were evaluated for their antiproliferative activity against a panel of human tumor cell lines.

La recherche d'une méthode de synthèse de phénylséléno phosphate d'alkyle (RO)::(2)P(O)CH::(2)SePh a permis de trouver un nouveau réactif de Grignard (ETO)::(2)P(O)CH::(2)MGCL. Les propriétés de ce nouveau réactif ont été étudiées et comparées à celles des autres organométalliques correspondants connus lithiens et cuivreux. Ce réactif de Grignard conduit à une synthèse originale de sélénophosphonates. Utilisation des phosphates d'alkyle comme agents d'alkylation pour la synthèse de dithioesters. Des énephosphoramides fonctionnels ont été obtenus pour la première fois et la réactivité carbonique de l'un d'entre eux a été étudiée

The research described in this thesis originated from an idea to develop new body protection for the sport of fencing. The ultimate goal is to develop body armour which would be flexible, wearable, washable, light and breathable, offer protection from injuries and cover the entire body of a sportsman. A new material which exhibits shear thickening behaviour has been specially developed for this purpose in the process of this investigation. The material was designed and synthesised as a soft polymeric system which is flexible, chemically stable and able to increase the value of its modulus of elasticity upon impact at a high strain rate, while remaining in its soft gel-like elastomeric state when low strain rate deformation is applied. The polymeric system that has been developed is based on interpenetrating polymeric networks (IPN) of immiscible polyurethane/urea-ester/ether and poly(boron)n(dimethylsiloxane)m (where on average m ≈ 16 n). In addition, as the polydimethylsilane (PDMS) based polymeric system strongly tends to phase separation, the siloxane polymeric network was chemically cross-linked to the polyurethane polymeric network through polyurethane chemical cross-link-bridges. In order to introduce polyurethane cross-links to a siloxane-based polymeric network, some of the attached methyl groups in the PDMS polymeric backbone were substituted by ε-pentanol groups. The resulting polymeric system combines properties of an alternating copolymer with IPN. The actual substitution of the methyl groups of PDMS into alternating ε-pentanol groups was performed by Grignard reaction of trifunctional chlorosilane monomers, magnesium and 1,5-dibromopentane. Chemical analytical techniques like FT-IR, 13C NMR and 1H NMR spectroscopy were used to reveal the chemical structure of the synthesised polymeric network. The mechanical and dynamical properties of the obtained polymeric system were analysed by dynamic mechanical analysis (DMA). This part of the investigation indicated that the novel polymeric system exhibited shear thickening behaviour, but only at a narrow diapason of deformations (i.e., deformations between 2 to 3 % of the length of the sample). At this limited diapason of deformation an effective increase of the modulus of elasticity from 6 MPa (at lower frequencies, i.e., up to ≤6 Hz of the applied oscillating stress) to 65 MPa (at frequencies between 12.5 to 25 Hz) was obtained. However, no increase in the modulus of elasticity was recorded at deformations below 1.5 % or above 3.5 % of length of the sample at the same frequencies (0 to 25Hz) of the applied oscillating stress.

碩士
國立臺灣師範大學
化學系
84
Reactions of β-nitrostyrene and Grignard Reagents gave 1,4-adducts(nitronates) at -20 ℃.Futher manipulation of the nitronate were demostrated as follows:(1) treatment of the nitronates with 0 ℃ 5% HCl(aq) generated nitroalkanes. (2) tretment of the nitronates with 0 ℃ 85% H2SO4(aq)generated caboxylic acids. (3) tretment of the nitronates with 0℃ conc. HX(aq) generated hydroximoyl halides. Hydroximoyl halides could convert to nitrile oxide in the presence of base such as triethyl amine, followed by 1,3-dipolar cycloaddition with alkenes or alkynes to give 2-isoxazolines or isoxazoles.

碩士
國立臺灣師範大學
化學系
84
1,1-二苯基-2-硝基乙烯及其衍生物與格里納試劑反應,經稀酸水溶液水 解後得到屬於1,4-加成的產物o 例如一級的硝基烷類及 oxime 化合物;但 如果將反應所形成的intermediate-nitronate 加入強酸中,則進行 Nef 或 Meyer reaction, 預期為羰基或酸化合物,但在反應的過程中,卻意外 的捕抓住鹵素離子,而形成中間產物 hydroximoylhalides. hydroximoyl halides 可和鹼作用脫去 HX 而生成 nitrile oxides. nitrileoxides 和烯或炔進行 1,3-dipolar cycloaddition 的反應,得到具有專一性或高 選擇性的 2-isoxazoline 或 isoxazole.由於立體障礙因素,使得 1,1,2-三苯基-2-硝基乙烯與三級丁基或二及異丙基等之立障較大之格里 納試劑反應時,改以自由基的方式進行反應,整個反應過程可知,苯基及烷 基扮演著相當重要的角色o 1,1-Diphenyl-2-nitroethylene and their derivatives can react with Grignandreagents to form 1,4-addition products such as primary nitroalkanes and oximes after workup with dilute aqueous acid solution. On the other hand,if the intermediate-nitronates are added to ice cold 85% H2SO4 or concentratedHX(aq) solution will undergo Nef or Meyer reaction and the expected producted are carbonyl compounds or carpoxylic acids. Surprisingly, the hydroximoyl Halides are formed if the reactive intermediate trap the halogen ions. Hydroximoyl halides will convert into nitrile oxides in the presence of base.It is known that nitrile oxides under 1,3-dipolar cycloaddition with alkenes oralkynes to generate stereospecific or steroselective of 2-isoxalolines orisoxazoles.1,1,2-Triphenyl-2-nitroethylene react with Grignard reagents to give free radical or SET products if the organomagensium halides belong to teritary orsecondary reagents. the different results can be ascribed to the steric effectof the phenyl and bulky alkyl groups.

博士
國立臺灣大學
化學學系
82
The nickel-catalyzed reactions of allylic dithioketals with excess MeMgI give the geminal dimethylation products in good yields. t-Butylstyrenes and related compounds are synthesized stereoselectively. The formation of a chelation complex results in the enhancement of the reactivity of the nickel-catalyzed cross coupling reaction of aliphatic dithioacetals with Grignard reagents. Various neighboring heteroatom substituents can facilitate the olefination of a dithioacetal group giving the corresponding olefins regioselectively. (2S,3S)-1,4-di-tert- alkoxy-2,3-butanediols are obtained from the reactions of (2S,3 S)-threitol bisketals with Grignard reagents. The size of the alkoxy substituents can be easily tuned. The reactions of benzylic acetals, prepared from (2S,3S)-1,4-di-tert-alkoxy-2,3- butanediols and aromatic aldehyde, with aryl or secondary or sterically hindered Grignard reagents give the corresponding alkylative ring- opening products in high diastereoselectivity (%de=92-99%).

碩士
國立中興大學
化學系所
100
Transtion-metal-Catalyzed Cross-Coupling reaction is a powerful strategy for Constracting Carbon-Carbon and Carbon-heteroatom bonds. In the first part of this thesis, the direct meta C-H functionalization of C-H bond of aromatic ring is introduced. The combination of iridium-Catalyzed C-H activation and sequential functionalization of the resulting aryl boronic ester is an excellent approach for regioselection meta C-H functionalization of aromatic C-H bond. The second part of this thesis, although the Grignard reagents have been used as nucleophiles to react with aryl disulfides, leading the corresponding aryl thioethers, these are some drawbacks in these systems. Fisrt, aryl disulfides and thiosulfonates must be prepared in advance. Second, from the atom economic point of view, an equivalent of sulfur moiety will be generated as the byproducts. Thus, it is desirable to develop a convenient method for the synthesis of aryl thioethers through the reaction of Grignard reagents with thiols without the preparation of aryl disulfides. The second of this thesis, the NCS-promoted coupling reaction of Grignard reagents with thiols is reported.

博士
國立臺灣師範大學
化學系
104
Abstract This thesis consists of two independent parts. Independently, each part has its own preface, motivation, discussion, experimental results, and conclusions. Research and discussion for the mechanism of the reaction between the Grignard reagent and β-nitrostyrene derivatives are discussed in the first section. Polar addition or single electron transfer has been a controversial issue in the Grignard reaction pathway. The previous studies showed the Grignard reagent with greater steric-hindered functionality, such as t-BuMgCl in polar solvent including THF, favors the SET reaction route; while the Grignard reactions with less steric crowding in non-polar solvents, such as ether were found to be via the polar addition route. The results of reactions of 1,1,2-triphenyl-2-nitroethane or β-nitrostyrene derivatives with several different kinds of Grignard reagents were discussed in this research work. Under -25℃inTHF, two different products were found to be 1,4-addition product via polar addition route and 1,8-addition product via single transfer electron route. 1,8-Addition product resulting from the Grignard reaction is novel since hitherto was not described. One-pot preparation of Chroman is the subject of the second part of this thesis. This one-pot synthesis was carried out under the following reaction condition to produce 3-nitro-chroman as an exclusive product with excellent yield. As such, salicylicaldehyde and cyclohexylamine along with nitromethane in (4:5:1) mixed in glacial acetic acid (2.0 ml) at 80-90℃for 24 hours. Therefore, a novel method for the preparation of Chroman was invented. Key word: polar addition、Single Electron Transfer、1,1,2-Triphenyl-2-nitroethene、Chroman

Cette thèse se compose en deux parties: Première Partie: La conception et la synthèse d’analogues pyrrolidiniques, utilisés comme agents anticancéreux, dérivés du FTY720. FTY720 est actuellement commercialisé comme médicament (GilenyaTM) pour le traitement de la sclérose en plaques rémittente-récurrente. Il agit comme immunosuppresseur en raison de son effet sur les récepteurs de la sphingosine-1-phosphate. A fortes doses, FTY720 présente un effet antinéoplasique. Cependant, à de telles doses, un des effets secondaires observé est la bradycardie dû à l’activation des récepteurs S1P1 et S1P3. Ceci limite son potentiel d’utilisation lors de chimiothérapie. Nos précédentes études ont montré que des analogues pyrrolidiniques dérivés du FTY720 présentaient une activité anticancéreuse mais aucune sur les récepteurs S1P1 et S1P3. Nous avons soumis l’idée qu’une étude relation structure-activité (SARs) pourrait nous conduire à la découverte de nouveaux agents anti tumoraux. Ainsi, deux séries de composés pyrrolidiniques (O-arylmethyl substitué et C-arylmethyl substitué) ont pu être envisagés et synthétisés (Chapitre 1). Ces analogues ont montré d’excellentes activités cytotoxiques contre diverses cellules cancéreuses humaines (prostate, colon, sein, pancréas et leucémie), plus particulièrement les analogues actifs qui ne peuvent pas être phosphorylés par SphK, présentent un plus grand potentiel pour le traitement du cancer sans effet secondaire comme la bradycardie. Les études mécanistiques suggèrent que ces analogues de déclencheurs de régulation négative sur les transporteurs de nutriments induisent une crise bioénergétique en affamant les cellules cancéreuses. Afin d’approfondir nos connaissances sur les récepteurs cibles, nous avons conçu et synthétisé des sondes diazirine basées sur le marquage d’affinité aux photons (méthode PAL: Photo-Affinity Labeling) (Chapitre 2). En s’appuyant sur la méthode PAL, il est possible de récolter des informations sur les récepteurs cibles à travers l’analyse LC/MS/MS de la protéine. Ces tests sont en cours et les résultats sont prometteurs. Deuxième partie: Coordination métallique et catalyse di fonctionnelle de dérivés β-hydroxy cétones tertiaires. Les réactions de Barbier et de Grignard sont des méthodes classiques pour former des liaisons carbone-carbone, et généralement utilisées pour la préparation d’alcools secondaires et tertiaires. En vue d’améliorer la réaction de Grignard avec le 1-iodobutane dans les conditions « one-pot » de Barbier, nous avons obtenu comme produit majoritaire la β-hydroxy cétone provenant de l’auto aldolisation de la 5-hexen-2-one, plutôt que le produit attendu d’addition de l’alcool (Chapitre 3). La formation inattendue de la β-hydroxy cétone a également été observée en utilisant d’autres dérivés méthyl cétone. Étonnement dans la réaction intramoléculaire d’une tricétone, connue pour former la cétone Hajos-Parrish, le produit majoritaire est rarement la β-hydroxy cétone présentant la fonction alcool en position axiale. Intrigué par ces résultats et après l’étude systématique des conditions de réaction, nous avons développé deux nouvelles méthodes à travers la synthèse sélective et catalytique de β-hydroxy cétones spécifiques par cyclisation intramoléculaire avec des rendements élevés (Chapitre 4). La réaction peut être catalysée soit par une base adaptée et du bromure de lithium comme additif en passant par un état de transition coordonné au lithium, ou bien soit à l’aide d’un catalyseur TBD di fonctionnel, via un état de transition médiée par une coordination bidenté au TBD. Les mécanismes proposés ont été corroborés par calcul DFT. Ces réactions catalytiques ont également été appliquées à d’autres substrats comme les tricétones et les dicétones. Bien que les efforts préliminaires afin d’obtenir une enantioselectivité se sont révélés sans succès, la synthèse et la recherche de nouveaux catalyseurs chiraux sont en cours.
This thesis consists of two parts: Part 1: Design and synthesis of constrained azacyclic pyrrolidine analogues of FTY720 as anticancer agents FTY720 is presently marketed as a drug (GilenyaTM) for the treatment of relapsing-remitting multiple sclerosis. It functions as an immunosuppressant due to its effect on sphingosine-1-phosphate (S1P) receptors. At higher doses, FTY720 also has antineoplastic actions. However, at such doses it induces bradycardia due to the activation of the S1P1 and S1P3 receptors. This limits its potentical to be used as a cancer therapy in humans. Our previous studies have shown that some constrained pyrrolidine analogues of FTY720 have anticancer activity but no activity toward S1P1 and S1P3 receptors. We reasoned that a study of the structure-activity relationships (SARs) could lead to the discovery of new effective antitumor agents. Thus, two series of constrained analogues (O-arylmethyl-substituted pyrrolidines and C-aryl-substituted pyrrolidines) were designed and synthesized (Chapter 1). These analogues showed excellent cytotoxic activity against various human cancer cells (prostate, colon, breast, pancreas and leukemia). Especially, several active analogues, which cannot be phosphorylated by SphK, have the potency to be further studied in the treatment of cancer without inducing bradycardia. Mechanistic studies suggest that these constrained analogues trigger down-regulation of nutrient transporters, which induce a bioenergetic crisis and the cancer cells starve to death. To further investigate their target receptors, we have designed and synthesized diazirine based photo-affinity labeling (PAL) probes (Chapter 2). Aided by the PAL technique, information regarding the target receptor could be obtained through LC/MS/MS protein analysis. These tests are in progress and the preliminary results appear promising. Part 2: Metal coordination-controlled and bifunctional catalysis toward tertiary β-ketols The Barbier and Grignard reactions are classical methods to form carbon-carbon bonds, and generally used to prepare secondary or tertiary alcohols. In an attempt to perform a Grignard reaction with n-butyl iodide under Barbier one-pot conditions, we obtained major product β-hydroxyl ketol from the self-aldol reaction of 5-hexen-2-one, rather than the expected addition alcohol product (Chapter 3). The unusual β-ketol formation was also observed using other methyl ketone substrates. Interestingly, in an intramolecular reaction of a triketone substrate, which is well known to give the Hajos-Parrish ketone, the favored product was a rarely studied β-ketol with the hydroxyl group at axial position. Intrigued by these results, after systematic reaction condition studies, we developed two new methods toward the catalytic synthesis of specific β-ketols by intramolecular cylcization in high yield and selectivity (Chapter 4). The reaction can be catalyzed either by a suitable base and lithium bromide as the additive, through a lithium pre-organized transition state or by a bifunctional catalyst TBD (triazabicyclodecene), through a TBD mediated bidentate transition state. The proposed mechanisms were corroborated by DFT computation. These catalytic reactions were also extended to other triketone and diketone substrates. Although the initial efforts to achieve enantioselectivity were not successful, they merit further study of the synthesis and investigation of new chiral catalysts.

In Michael J. Krische research group we are developing new transition metal catalyzed Carbon-Carbon (C-C) forming reactions focusing on atom economy and byproduct free, environmental friendly approaches. We have developed a broad family of C-C bond forming hydrogenations with relative and absolute stereocontrol which provide an alternative to stoichiometric organometallic reagents in certain carbonyl and imine additions. Inspiring from the group work my goal was to develop new reactions, extend the scope of our group chemistry and their application towards synthesis of biologically active natural products. I have been part of enantioselective Rh catalyzed Aldol reaction of vinyl ketones to different aldehydes. Also, we have found that iridium catalyzed transfer hydrogenation of allylic acetates in the presence of aldehydes or alcohols results in highly enantioselective carbonyl allylation under the conditions of transfer hydrogenative. Based on this reactivity a concise enantio- and diastereoselective synthesis of 1,3-polyols was achieved via iterative chain elongation and bidirectional iterative asymmetric allylation was performed, which enables the rapid assembly of 1,3-polyol substructures with exceptional levels of stereocontrol. The utility of this approach stems from the ability to avoid the use of chirally modified allylmetal reagents, which require multistep preparation, and the ability to perform chain elongation directly from the alcohol oxidation level. This approach was utilized for the total synthesis of (+)-Roxaticin from 1,3-propanediol in 20 longest linear steps and a total number of 29 manipulations. Further, advancements were made in iridium catalyzed C-C bond formation under transfer hydrogenation. While methallyl acetate does not serve as an efficient allyl donor, the use of more reactive leaving group in methallyl chloride compensate for the shorter lifetime of the more highly substituted olefin π-complex. Based on this insight into the requirements of the catalytic process, highly enantioselective Grignard-Nozaki-Hiyama methallylation is achieved from the alcohol or aldehyde oxidation levels. Also, a catalytic method for enantioselective vinylogous Reformatsky- type aldol addition was developed in which asymmetric carbonyl addition occurs with equal facility from the alcohol or aldehyde oxidation level. Good to excellent levels of regioselectivity and uniformly high levels of enantioselectivity were observed across a range of alcohols and aldehydes.
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