Bibliografías temáticas / Chemoselectivity

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Literatura académica sobre el tema "Chemoselectivity"

Autor: Grafiati
Publicado: 4 de junio de 2021
Última modificación: 6 de febrero de 2022

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Artículos de revistas sobre el tema "Chemoselectivity"

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Wang, Juping, Kangcheng Zheng, Ting Li y Xiaojing Zhan. "Mechanism and Chemoselectivity of Mn-Catalyzed Intramolecular Nitrene Transfer Reaction: C–H Amination vs. C=C Aziridination". Catalysts 10, n.º 3 (4 de marzo de 2020): 292. http://dx.doi.org/10.3390/catal10030292.

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The reactivity, mechanism and chemoselectivity of the Mn-catalyzed intramolecular C–H amination versus C=C aziridination of allylic substrate cis-4-hexenylsulfamate are investigated by BP86 density functional theory computations. Emphasis is placed on the origins of high reactivity and high chemoselectivity of Mn catalysis. The N p orbital character of frontier orbitals, a strong electron-withdrawing porphyrazine ligand and a poor π backbonding of high-valent MnIII metal to N atom lead to high electrophilic reactivity of Mn-nitrene. The calculated energy barrier of C–H amination is 9.9 kcal/mol lower than that of C=C aziridination, which indicates that Mn-based catalysis has an excellent level of chemoselectivity towards C–H amination, well consistent with the experimental the product ratio of amintion-to-aziridination I:A (i.e., (Insertion):(Aziridination)) >20:1. This extraordinary chemoselectivity towards C–H amination originates from the structural features of porphyrazine: a rigid ligand with the big π-conjugated bond. Electron-donating substituents can further increase Mn-catalyzed C–H amination reactivity. The controlling factors found in this work may be considered as design elements for an economical and environmentally friendly C–H amination system with high reactivity and high chemoselectivity.
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Ho, Tse-Lok. "Chemoselectivity of organometallic reactions". Tetrahedron 41, n.º 1 (enero de 1985): 3–86. http://dx.doi.org/10.1016/s0040-4020(01)83470-0.

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Marigo, Mauro y Paolo Melchiorre. "Chemoselectivity in Asymmetric Aminocatalysis". ChemCatChem 2, n.º 6 (7 de junio de 2010): 621–23. http://dx.doi.org/10.1002/cctc.201000110.

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Zhang, Sai, Zhaoming Xia, Ting Ni, Huan Zhang, Chao Wu y Yongquan Qu. "Tuning chemical compositions of bimetallic AuPd catalysts for selective catalytic hydrogenation of halogenated quinolines". Journal of Materials Chemistry A 5, n.º 7 (2017): 3260–66. http://dx.doi.org/10.1039/c6ta09916e.

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Au1−xPdx bimetallic catalysts with low Pd entities on CeO2 nanorods delivered high activity and chemoselectivity for hydrogenation of halogenated quinolines. Improved chemoselectivity could be attributed to the selective adsorption configurations of halogenated quinolines on Au via tilted orientation rather than on Pd via flat orientation.
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Nahmany, Moshe y Artem Melman. "Chemoselectivity in reactions of esterification". Organic & Biomolecular Chemistry 2, n.º 11 (2004): 1563. http://dx.doi.org/10.1039/b403161j.

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Sinha, S. C., E. Keinan y J. L. Reymond. "Antibody-catalyzed reversal of chemoselectivity." Proceedings of the National Academy of Sciences 90, n.º 24 (15 de diciembre de 1993): 11910–13. http://dx.doi.org/10.1073/pnas.90.24.11910.

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Thygesen, Mikkel B. y Knud J. Jensen. "ChemInform Abstract: Chemoselectivity and Glyconanoparticles". ChemInform 44, n.º 11 (8 de marzo de 2013): no. http://dx.doi.org/10.1002/chin.201311226.

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Barak-Kulbak, Einav, Kerem Goren y Moshe Portnoy. "Advantages of polymer-supported multivalent organocatalysts for the Baylis-Hillman reaction over their soluble analogues". Pure and Applied Chemistry 86, n.º 11 (1 de noviembre de 2014): 1805–18. http://dx.doi.org/10.1515/pac-2014-0721.

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Abstract Immobilization of well-defined catalytic units onto insoluble support promises significant benefits, but frequently results in a reduced activity and selectivity of the heterogenized catalysts. Recently, we showed that introduction of a dendritic spacer between the support and the units could remedy the compromised activity and/or selectivity of heterogenized catalysts and, in particular, of the systems based on N-alkylated imidazoles. These catalysts exhibit an outstanding multivalency effect on the activity in the Baylis-Hillman reaction, while preserving very high chemoselectivity. In order to better understand this remarkable effect, we decided to synthesize and examine soluble analogues of the supported systems. These soluble catalysts display poor chemoselectivity, although it improves with the increase of the dendritic generation. Though the consumption of the limiting aldehyde reactant (conversion) displays the opposite trend, experiments demonstrated that the chemoselectivity is generation-dependent rather than conversion-dependent. A hydrophobic “pocket” effect was implicated as responsible for the differences between the polystyrene-bound and the soluble catalysts. An MS analysis of the crude reaction mixture revealed that the formation of multiple adducts, which incorporate several enone and several nitrobenzaldehyde fragments into a single molecular structure (as opposed to one-to-one stoichiometry of the Baylis-Hillman reaction), is responsible for the decline in the chemoselectivity.
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Ghinato, Simone, Giuseppe Dilauro, Filippo Maria Perna, Vito Capriati, Marco Blangetti y Cristina Prandi. "Directed ortho-metalation–nucleophilic acyl substitution strategies in deep eutectic solvents: the organolithium base dictates the chemoselectivity". Chemical Communications 55, n.º 54 (2019): 7741–44. http://dx.doi.org/10.1039/c9cc03927a.

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Yu, Haifeng, Dewen Dong, Yan Ouyang y Qun Liu. "Chemoselective thioacetalization with odorless 2-(1,3-dithian-2-ylidene)-3-oxobutanoic acid as a 1,3-propanedithiol equivalent". Canadian Journal of Chemistry 83, n.º 10 (1 de octubre de 2005): 1741–45. http://dx.doi.org/10.1139/v05-184.

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Odorless 2-(1,3-dithian-2-ylidene)-3-oxobutanoic acid (1c) was prepared and investigated in the thioacetalization of carbonyl compounds as a 1,3-propanedithiol equivalent. The results showed that the thioacetalization of various carbonyl compounds 2 with 1c proceeded smoothly and afforded the corresponding dithioacetals 3 in high yields (up to 99%) in the presence of acetyl chloride at room or reflux temperatures. Moreover, the thioacetalization exhibited high chemoselectivity between aldehydes and ketones. Key words: chemoselectivity, 2-(1,3-dithian-2-ylidene)-3-oxobutanoic acid, α-oxo ketene dithioacetal, 1,3-propanedithiol equivalent, thioacetalization.
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Tesis sobre el tema "Chemoselectivity"

1

Hedfors, Cecilia. "Lipase chemoselectivity - kinetics and applications". Licentiate thesis, KTH, School of Biotechnology (BIO), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10232.

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A chemoselective catalyst is preferred in a chemical reaction where protecting groups otherwise are needed. The two lipases Candida antarctica lipase B and Rhizomucor miehei lipase showed large chemoselectivity ratios, defined as (kcat/KM)OH / (kcat/KM)SH, in a transacylation reaction with ethyl octanoate as acyl donor and hexanol or hexanethiol as acyl acceptor (paper I). The chemoselectivity ratio of the uncatalyzed reaction was 120 in favour of the alcohol. Compared to the uncatalyzed reaction, the chemoselectivity was 730 times higher for Candida antarctica lipase B and ten times higher for Rhizomucor miehei lipase. The KM towards the thiol was more than two orders of magnitude higher than the KM towards the corresponding alcohol. This was the dominating contribution to the high chemoselectivity displayed by the two lipases. In a novel approach, Candida antarctica lipase B was used as catalyst for enzymatic synthesis of thiol-functionalized polyesters in a one-pot reaction without using protecting groups (paper II). Poly(e-caprolactone) with a free thiol at one of the ends was synthesized in an enzymatic ring-opening polymerization initiated with mercaptoethanol or terminated with either 3-mercaptopropionic acid or g-thiobutyrolactone.

 

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Morey, James Vaughan. "Controlling the chemoselectivity of directed metallation". Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612284.

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Malmgren, Joel. "Iodonium Salts : Preparation, Chemoselectivity and Metal-Catalyzed Applications". Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-107694.

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This thesis concerns the preparation and use of diaryliodonium salts. In Project I various unsymmetrical diaryliodonium salts were reacted with three different nucleophiles in order to study the chemoselectivity of the reactions of the salts. The main focus of this project was to gain a deeper understanding of the underlying factors that affect the chemoselectivity in transition metal-free arylation reactions. They were found to be very nucleophile-dependent. Some nucleophiles were very sensitive to electronic effects, whereas others were sensitive to steric factors. Ultimately, some arenes are never transferred. A very interesting scrambling reaction was also observed under the reaction conditions, where unsymmetrical diaryliodonium salts form symmetrical salts in situ. Project II details the preparation of N-heteroaryliodonium salts via a one-pot procedure. The salts were designed so that the N-heteroaryl moiety was selectively transferred in applications both with and without transition metals. The chemoselectivity was demonstrated by selective transfer of the pyridyl group onto two different nucleophiles. The third project in the thesis discusses the synthesis of alkynyl(aryl)iodonium salts and alkynylbenziodoxolones from arylsilanes. This protocol could potentially be a very useful complement to the existing procedures, in which boronic acids are used. The last part of the thesis (Project IV) describes a C-2 selective arylation of indoles where diaryliodonium salts were used in combination with hetero-geneous palladium catalysis. This transformation was performed in water at ambient temperature to 50 °C, and tolerated variations of both the indole and the diaryliodonium salt. Importantly, several N-H indoles could be arylated. The MCF-supported Pd-catalyst showed very little leaching and it was demonstrated that the main part of the reaction occurred via heterogeneous catalysis.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Accepted.

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Volkov, Alexey. "Catalytic Amide Reductions under Hydrosilylation Conditions". Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-129028.

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This thesis covers the development of catalytic methodologies for the mild and chemoselective reductions of amides. The first part of the thesis describes the use of a Fe(II)/NHC catalyst for the deoxygenation of aromatic tertiary amides to corresponding amines. The protocol is characterized by low catalyst loading, mild reaction conditions and the use of air and moisture stable polymethylhydrosilaxane (PMHS) as the hydride source. The second part concerns the development of a protocol for the room temperature deoxygenation of a wide range of tertiary amides to amines using catalytic amounts of Et2Zn and LiCl together with PMHS. The system displayed high levels of chemoselectivity tolerating various reducible groups such as nitro, nitrile, and olefin functionalities, and was shown to be applicable for the reduction of aromatic, heteroaromatic and aliphatic tertiary amides. The attempts to expand the scope of the Fe-based protocol to accommodate benzylic tertiary amides led to the development of a transition metal-free catalytic system based on KOtBu for the formation of enamines. The final products constitute an important class of precursors for a wide range of valuable compounds in organic chemistry. Moreover, avoiding the use of transition metals in the protocol allowed the desired products to be obtained without the hazardous metal contaminants. The last chapter of the thesis describes the Mo(CO)6-catalyzed hydrosilylation of amides. The Mo-based catalyst was proven to mediate the deoxygenation of α,β-unsaturated tertiary and secondary amides to the corresponding allylamines without reduction of the olefinic bonds. Further development of the catalytic system revealed an unprecedented chemoselectivity in the hydrosilylation of aromatic and certain aliphatic tertiary amides in the presence of a variety of reducible groups along with aldehydes and imines that were tolerated for the first time. Moreover, it was possible to control the reaction outcome by variation of the reaction temperature to obtain either amines or aldehydes as the major products. The synthetic utility of the developed Mo(CO)6-catalyzed protocols was further demonstrated in the synthesis of the pharmaceuticals Naftifine and Donepezil.
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Kamikawa, Takashi. "Enantioselectivity and Chemoselectivity in Palladium-Catalyzed Grignard Cross-Coupling of Aryl Triflates". 京都大学 (Kyoto University), 1998. http://hdl.handle.net/2433/157165.

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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである
Kyoto University (京都大学)
0048
新制・論文博士
博士(理学)
乙第9788号
論理博第1334号
新制||理||1061(附属図書館)
UT51-98-G387
(主査)教授 林 民生, 教授 鈴木 仁美, 教授 大須賀 篤弘
学位規則第4条第2項該当
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Marth, Gabriella. "The synthesis of polyfunctional pyrroles and the investigation of the chemoselectivity of their reactions". Thesis, University of Sunderland, 2009. http://sure.sunderland.ac.uk/3694/.

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Polyfunctional pyrroles are interesting heterocyclic intermediates as they have a range of reactive centres and the chemoselectivity of their reactions under a range of conditions, is therefore, of much interest. Polyfunctionalised heterocycles are relatively difficult to prepare, but the reactions of these substituted pyrroles allow access to a wide variety of new substituted heterocyclic compounds via these intermediates. The aim of this project was to synthesise polyfunctional pyrroles in order to investigate their use in the preparation of libraries and compounds with known biological activity. The synthesis and initial investigation of the regioselectivity of polyfunctional pyrroles, such as 3,5-dichloro-1H-pyrrole-2,4-dicarboxaldehyde, has previously been described; this work investigated only nucleophilic substitutions. We have investigated the chemoselectivity of the reaction of these pyrroles with a range of reagents and a number of pyrrole derivatives were synthesised via selective functional group transformations. All new compounds were fully characterised by spectroscopic and elemental analysis. Another aim of this project was to discover novel agents that inhibit VEGF receptors using structure based drug design. We have identified hit compounds and synthesised them using regioselective reactions of functional groups present on the pyrrole ring. The compounds were tested for anti-proliferative activity against the HaCaT, human keratinocyte cell line, and also against HT29 and CaCo-2, human colon cell lines using the MTT assay.
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Sandford, Christopher. "The reactivity and chemoselectivity of nucleophilic boronate complexes : applications in cross-coupling, fluorination and trifluoromethylation". Thesis, University of Bristol, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.730846.

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Blanco, Jiménez Carolina. "Norbornene functionalization through asymmetric pd- and rh-catalyzed carbonylation processes". Doctoral thesis, Universitat Rovira i Virgili, 2010. http://hdl.handle.net/10803/9109.

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Esta tesis se ha centrado en el estudio de las reacciones de carbonilación de norborneno catalizada por metales. Este sustrato puede ser funcionalizado a través de este proceso, empleando sistemas catalíticos y condiciones de reacción adecuadas, en productos intermedios con aplicación en la industria de perfumes y química fina. En este trabajo se han llevado a cabo estudios en la reacción de metoxicarbonilación de norborneno catalizada por paladio empleando ligandos monofosfina y difosfina logrando un importante control de la selectividad hacia la formación del producto deseado. Algunos aspectos mecanísticos de esta reacción han sido desarrollados empleando métodos de resonancia magnética nuclear que incluyen experimentos de alta presión. Finalmente, se ha estudiado la reacción de hidroformilación asimétrica de norborneno catalizada por complejos de rodio usando ligandos difosfito derivados de carbohidrato. Estos sistemas catalíticos han mostrado alta actividad y selectividad con excesos enantioméricos moderados.
This thesis focuses on the study of the metal-catalyzed carbonylation of norbornene. The transformation of this substrate in esters and aldehydes offers potential applications for the production of valuable compounds in fine chemistry and perfumery industry. In this work we have performed studies on the palladium-catalyzed methoxycarbonylation of norbornene bearing monodentate and bidentate phosphine ligands achieving an important control of the selectivity towards the formation of the desired product. Mechanistic aspects of this reaction have been developed using nuclear magnetic resonance methods, including High-Pressure techniques. Finally, we have studied the asymmetric rhodium-catalyzed hydroformylation of norbornene using chiral 1,3-diphosphites ligands derived from carbohydrates. These catalytic systems have shown high activities with excellent stereoselectivities and moderate enantioselectivities.
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Rueda, Becerril Montserrat. "Fluorination of alkyl radicals using electrophilic N-F reagents and investigation on the intramolecular chemoselectivity of alkoxy radicals". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/51510.

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The selective fluorination of organic molecules has become increasingly important for the pharmaceutical and agrochemical industries, given that the presence of this atom enhances the lipophilicity and bioavailability of molecules. Despite the extensive research in fluorine chemistry, there is a paucity of selective and safe sources of fluorine for radical reactions. I hereby present the investigation of N−F reagents as efficient fluorine atom transfer agents to alkyl radicals. Although most of the research presented in this work focuses on fluorination methodologies, a study on the intramolecular chemoselectivity of alkoxy radicals is also discussed. Chapter 2 describes the exploratory work into the feasibility of transferring a fluorine atom to alkyl radicals from electrophilic sources of fluorine. Diacyl peroxides and t-butylperesters were homolyzed to generate alkyl radicals in the presence of different N−F fluorine sources. Primary, secondary, and tertiary fluoroalkanes were successfully synthesized under the reaction conditions. This methodology was successfully applied to the fluorination of a cholic acid derivative. In Chapter 3, photoredox catalysis was explored as an alternative method to generate alkyl radicals in the context of radical fluorination. Trisbipyridylruthenium (II) and visible light were utilized to promote the decarboxylative fluorination of phenoxyacetic acid derivatives. Electronwithdrawing groups on the aryl ring favoured the transformation, while electron-donating groups provided undesired products. An estrone derivative was successfully fluorinated with our visible-light mediated methodology. Additionally, transient absorption spectroscopy studies in collaboration with the Wolf group at the University of British Columbia, along with cyclic voltammetry experiments performed in collaboration with the Bizzotto group at the same institution, provided evidence to support an oxidative mechanism of the photocatalytic cycle. Chapter 4 describes a study to assess the chemoselectivity of alkoxy radical cyclizations onto silyl enol ethers, when other radical pathways can occur. Cyclization of intramolecular competition substrates showed that 5-exo cyclization of alkoxy radicals onto silyl enol ethers were preferred over 5-exo cyclizations onto terminal, disubstituted and trisubstituted alkenes, as well as 1,5-hydrogen atom transfer reactions and β-fragmentations. Silyl enol ethers as alkoxy radical acceptors strongly favour 6-exo cyclization over 1,5-hydrogen atom transfer from an allylic position.
Science, Faculty of
Chemistry, Department of
Graduate
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10

Jalalian, Nazli. "Development and Applications of Hypervalent Iodine Compounds : Powerful Arylation and Oxidation Reagents". Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-75810.

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The first part of this thesis describes the efficient synthesis of several hypervalent iodine(III) compounds. Electron-rich diaryliodonium salts have been synthesized in a one-pot procedure, employing mCPBA as the oxidant. Both symmetric and unsymmetric diaryliodonium tosylates can be isolated in high yields. An in situ anion exchange also enables the synthesis of previously unobtainable diaryliodonium triflates. A large-scale protocol for the synthesis of a derivative of Koser’s reagent, that is an isolable intermediate in the diaryliodonium tosylate synthesis, is furthermore described. The large-scale synthesis is performed in neat TFE, which can be recovered and recycled. This is very desirable from an environmental point of view. One of the few described syntheses of enantiopure diaryliodonium salts is discussed. Three different enantiopure diaryliodonium salts bearing electron-rich substituents are synthesized in moderate to high yields. The synthesis of these three salts shows the challenge in the preparation of electron-rich substituted unsymmetric salts. The second part of the thesis describes the application of both symmetric and unsymmetric diaryliodonium salts in organic synthesis. A metal-free efficient and fast method for the synthesis of diaryl ethers from diaryliodonium salts has been developed. The substrate scope is wide as both the phenol and the diaryliodonium salt can be varied. Products such as halogenated ethers, ortho-substituted ethers and bulky ethers, that are difficult to obtain with metal-catalyzed procedures, are readily prepared. The mild protocol allows arylation of racemization-prone a-amino acid derivatives without loss of enantiomeric excess. A chemoselectivity investigation was conducted, in which unsymmetric diaryliodonium salts were employed in the arylation of three different nucleophiles in order to understand the different factors that influence which aryl moiety that is transferred to the nucleophile.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 5: Submitted. Paper 6: Manuscript.

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Capítulos de libros sobre el tema "Chemoselectivity"

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Thygesen, Mikkel B. y Knud J. Jensen. "Chemoselectivity and Glyconanoparticles". En ACS Symposium Series, 37–48. Washington, DC: American Chemical Society, 2011. http://dx.doi.org/10.1021/bk-2011-1091.ch003.

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Reetz, Manfred T. "Chemoselectivity in Reactions of Organotitanium Reagents with Carbonyl Compounds". En Reactivity and Structure: Concepts in Organic Chemistry, 75–112. Berlin, Heidelberg: Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-70704-9_3.

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"CHEMOSELECTIVITY PROBLEMS". En Evolution of Synthetic Pathways, 1–171. WORLD SCIENTIFIC, 1996. http://dx.doi.org/10.1142/9789812830173_0001.

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Ruasse, Marie-Francoise. "Stereo-, regio- and chemoselectivity of bromination of ethylenic compounds". En Advances in Organobromine Chemistry II, 100–112. Elsevier, 1995. http://dx.doi.org/10.1016/s0926-9614(05)80013-9.

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Cardenas-Lizana, Fernando y Mark Keane. "Toward Chemoselectivity: The Case of Supported Au for Hydrogen-Mediated Reactions". En Gold Catalysis, 415–64. Pan Stanford, 2015. http://dx.doi.org/10.1201/b19911-15.

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Flowers, R. A. II, T. V. Chciuk y C. O. Bartulovich. "2.2 Samarium-Mediated Reductions". En Free Radicals: Fundamentals and Applications in Organic Synthesis 2. Stuttgart: Georg Thieme Verlag KG, 2021. http://dx.doi.org/10.1055/sos-sd-233-00001.

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AbstractSamarium(II)-based reductants have been shown to be a group of very powerful reagents whose reactivity can be tuned significantly by the use of additives. The use of additives has been shown to greatly impact the rate, diastereoselectivity, chemoselectivity, and mechanism by which these reactions proceed, making these systems extremely useful and versatile. These reagents have been shown to promote several reactions including reductions of a range of functional groups and a variety of carbon–carbon bond forming reactions. More recently, initial work has demonstrated catalytic reactions of samarium(II)-based reductants. This chapter focuses on the chemistry of samarium diiodide (SmI2) and a few other samarium(II)-based reductants, with examples of the reactions they promote, both with and without the use of additives. Additionally, recent work on the mechanistic understanding of catalytic reactions using terminal reductants and a novel example of an approach employing radical relay that negates the use of a terminal reductant are presented.
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Lambert, Tristan H. "Functional Group Interconversion". En Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0004.

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Chaozhong Li of the Shanghai Institute of Organic Chemistry reported (J. Am. Chem. Soc. 2012, 134, 10401) the silver nitrate catalyzed decarboxylative fluorination of carboxylic acids, which shows interesting chemoselectivity in substrates such as 1. A related decarboxylative chlorination was also reported by Li (J. Am. Chem. Soc. 2012, 134, 4258). Masahito Ochiai at the University of Tokushima has developed (Chem. Commun. 2012, 48, 982) an iodobenzene-catalyzed Hofmann rearrangement (e.g., 3 to 4) that proceeds via hypervalent iodine intermediates. The dehydrating agent T3P (propylphosphonic anhydride), an increasingly popular reagent for acylation chemistry, has been used (Tetrahedron Lett. 2012, 53, 1406) by Vommina Sureshbabu at Bangalore University to convert amino or peptide acids such as 5 to the corresponding thioacids with sodium sulfide. Jianqing Li and co-workers at Bristol-Myers Squibb have shown (Org. Lett. 2012, 14, 214) that trimethylaluminum, which has long been known to effect the direct amidation of esters, can also achieve the direct coupling of acids and amines, such as in the preparation of amide 8. The propensity of severely hindered 2,2,6,6-tetramethylpiperidine (TMP) amides such as 9 to undergo solvolysis at room temperature has been shown (Angew. Chem. Int. Ed. 2012, 51, 548) by Guy Lloyd-Jones and Kevin Booker-Milburn at the University of Bristol. The reaction proceeds by way of the ketene and is enabled by sterically induced destabilization of the usual conformation that allows conjugation of the nitrogen lone pair with the carbonyl. Matthias Beller at Universität Rostock has found (Angew. Chem. Int. Ed. 2012, 51, 3905) that primary amides may be transamidated via copper(II) catalysis. The conditions are mild enough that an epimerization-prone amide such as 11 undergoes no observable racemization during conversion to amide 13. A photochemical transamidation has been achieved (Chem. Sci. 2012, 3, 405) by Christian Bochet at the University of Fribourg that utilizes 385-nm light to activate a dinitroindoline amide in the presence of amines such as 15, which produces the amide 16. Notably, photochemical cleavage of the Ddz protecting group occurs at a shorter wavelength of 300 nm.
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Actas de conferencias sobre el tema "Chemoselectivity"

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Sobkowski, Michal. "Diverse chemoselectivity during acylation of nucleosides". En XIVth Symposium on Chemistry of Nucleic Acid Components. Prague: Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 2008. http://dx.doi.org/10.1135/css200810277.

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Malmgren, Joel, Nazli Jalalian y Berit Olofsson. "Chemoselectivity Investigation on Arylations Using Diaryliodonium Salts". En 14th Brazilian Meeting on Organic Synthesis. São Paulo: Editora Edgard Blücher, 2013. http://dx.doi.org/10.5151/chempro-14bmos-r0265-1.

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Malmgren, Joel, Nazli Jalalian y Berit Olofsson. "Chemoselectivity Investigation in Arylations with Diaryliodonium Salts". En 14th Brazilian Meeting on Organic Synthesis. São Paulo: Editora Edgard Blücher, 2013. http://dx.doi.org/10.5151/chempro-14bmos-r0265-2.

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Hackenberger, Christian. "The power of chemoselectivity: Functional peptide- and protein-conjugates for extra- and intracellular targeting". En 35th European Peptide Symposium. Prompt Scientific Publishing, 2018. http://dx.doi.org/10.17952/35eps.2018.001.

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Zapata-Romero, Gilberto A., Markus Doerr y Martha C. Daza. "Lipase-catalyzed O-acylation of (RS)-propranolol is determined by the acyl group length". En VIII Simpósio de Estrutura Eletrônica e Dinâmica Molecular. Universidade de Brasília, 2020. http://dx.doi.org/10.21826/viiiseedmol2020130.

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We employed a computational modeling approach to study the Michaelis complexes of (R)- and (S)-propranolol with serine-acylated Candida antarctica lipase B using four acyl groups: ethanoyl, butanoyl, octanoyl and hexadecanoyl. Our methodology involves sampling Michaelis complex conformations, first through ensemble docking using consensus scoring, and second by molecular dynamics simulations employing a quantum mechanics/molecular mechanics approach. The conformations are then categorized into two classes of near attack conformations, according to the distance of (a) the amino and (b) the hydroxy group of propranolol to the catalytic residues. The relative populations of these two classes of conformations was found to be consistent with the experimentally-observed exclusive chemoselectivity toward O-acylation with ethanoyl. Furthermore, we predict that increasing the length of the hydrocarbon chain of the acyl group will cause O-acylation to be unfavorable.
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Luo, Xiaoling y Rong Chen. "Mechanism of the Rhodium-Catalyzed Hydroformylation of 4-(1-phenylvinyl)pyridine: A Detailed Computational Investigation of the Regioselectivity and Chemoselectivity". En 2015 2nd International Conference on Machinery, Materials Engineering, Chemical Engineering and Biotechnology. Paris, France: Atlantis Press, 2016. http://dx.doi.org/10.2991/mmeceb-15.2016.36.

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