Development And Evaluation Of Chiral Catalysts For Asymetric C C And C H Bond Forming Reactions

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Development And Evaluation Of Chiral Catalysts For Asymetric C C And C H Bond Forming Reactions

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Author : Christian Ebner
language : en
Publisher:
Release Date : 2012

Development And Evaluation Of Chiral Catalysts For Asymetric C C And C H Bond Forming Reactions written by Christian Ebner and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.

Development And Evaluation Of Chiral Catalysts For Asymmetric C C And C H Bond Forming Reactions

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Author : Christian Ebner
language : en
Publisher: Cuvillier Verlag
Release Date : 2012-03-05

Development And Evaluation Of Chiral Catalysts For Asymmetric C C And C H Bond Forming Reactions written by Christian Ebner and has been published by Cuvillier Verlag this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012-03-05 with Science categories.

This work was dedicated to the development and evaluation of new chiral catalysts for asymmetric C-C and C-H bond forming reactions. In the first part of the thesis an ESI-MS screening method is described, which allows the determination of a chiral catalyst´s selectivity in the palladium catalyzed asymmetric allylic alkylation by testing its racemic form. The value of this new method was demonstrated when different new aryl-PHOX-type ligands, which are not easily accessible in their enantiopure form, were evaluated. In the second part new PHOX-type ligands were tested in the iridium-catalyzed asymmetric hydrogenation of different unsaturated compounds. Although low activities and selectivities were found in most cases, one ligand showed promising results in the hydrogenation of allylic alcohols and imines. Furthermore air- and moisture-stable secondary phosphine oxide (SPO) containing bidentate ligands were tested in the palladium-catalyzed asymmetric allylic alkylation reaction. SPO,N-ligands bearing a PHOX type backbone were inactive in this transformation as they tend to form inactive palladium-bis-ligand complexes. SPO,P ligands however, were able to promote the desired reaction in a highly selective fashion although only low activities were found. During this work as well a new organo-catalyst, based on the structure of 2,3-dihydrobenzo[1,4]oxazine, was developed which allows for the asymmetric organo-catalyzed transfer-hydrogenation of α,β-unsaturated aldehydes. This catalyst was able to reduce for the first time β, β-diaryl acrylaldehydes with very good activities and high enantioselectivities. Moreover an ESI-MS based mechanistic study on the tripeptide catalyzed conjugate addition reaction of aldehydes to nitroolefins was carried out. By this all reaction intermediates postulated for an enamine mechanism have been detected. Furthermore the attack of the enamine onto the nitroolefin was found to be the selectivity determining step in this process. The last part of this work aimed for the asymmetric α -allylation of carbonyl compounds by a tandem-catalysis approach. An intensive screening of both the organo-catalyst and the palladium-ligand led to reaction conditions which allowed for the selective mono-allylation of ketones in high yields. The formation of a quaternary center by α -allylation of α -branched aldehydes was also achieved. However, only low enantiomeric excesses were obtained in this transformation for the different catalyst systems tested.

Enantioselective C C Bond Forming Reactions

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Author :
language : en
Publisher: Elsevier
Release Date : 2023-12-01

Enantioselective C C Bond Forming Reactions written by and has been published by Elsevier this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-12-01 with Science categories.

Enantioselective C-C Bond Forming Reactions: From Metal Complex-, Organo-, and Bio-catalyzed Perspectives, Volume 73 in the Advances in Catalysis series, highlights new advances in the field, with this new volume presenting interesting chapters on topics such as An introduction to Chirality, Metal-catalyzed stereoselective C-C-bond forming reactions, Enantioselective C-C bond forming reactions promoted by organocatalysts based on unnatural amino acid derivatives, Enantioselective C-C bond formation in complex multicatalytic system, Gold-based multicatalytic systems for enantioselective C-C Bond forming reactions, Novel enzymatic tools for C-C bond formation through the development of new-to-nature biocatalysis, and more. Provides the authority and expertise of leading contributors from an international board of authors Presents the latest release in Advances in Catalysis serials Updated release includes the latest information in the field

Asymmetric C C Bond Formation With Chiral Catalysts

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Author : Menapara Tusharkumar
language : en
Publisher: Alibaba
Release Date : 2023-05-25

Asymmetric C C Bond Formation With Chiral Catalysts written by Menapara Tusharkumar and has been published by Alibaba this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-05-25 with Medical categories.

The book "Asymmetric C-C Bond Formation with Chiral Catalysts" by Menapara Tusharkumar explores the fascinating field of asymmetric catalysis for carbon-carbon bond formation reactions. The book emphasizes on the use of chiral catalysts for the synthesis of enantiopure compounds that are critical for the development of new drugs, agrochemicals, and materials. The use of chiral catalysts offers high enantioselectivity and stereoselectivity, and therefore, provides an efficient way for the synthesis of organic compounds with desired stereochemistry. The book covers the design and synthesis of chiral catalysts, including ligands and transition metal complexes. The author discusses the chemical properties of chiral catalysts and their influence on the reaction mechanisms and stereoselectivity. The book also highlights the importance of molecular recognition in asymmetric catalysis and its application in various catalytic reactions. The book covers various types of asymmetric catalysis, including organocatalysis, metal-catalyzed reactions, and enzymatic catalysis. It discusses the advantages and limitations of each type of catalysis and provides examples of their applications in organic synthesis. The author also emphasizes the importance of green chemistry and sustainability in asymmetric catalysis. The book covers a range of topics related to asymmetric C-C bond formation, including diastereoselectivity, substrate specificity, kinetic resolution, and stereochemical control. The book also provides examples of the synthesis of natural products, alkene coupling, palladium-catalyzed cross-coupling reactions, oxidative coupling reactions, Diels-Alder reactions, and Michael addition reactions using chiral catalysts. Overall, "Asymmetric C-C Bond Formation with Chiral Catalysts" is an essential reference for organic chemists, catalysis researchers, and students who are interested in asymmetric catalysis, enantioselective synthesis, and stereochemistry. The book provides a comprehensive overview of the field, including recent advances and challenges, and offers practical guidance for the design and optimization of chiral catalysts for asymmetric C-C bond formation reactions.

Asymmetric Catalysis Of Carbon Carbon Bond Forming Reactions

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Author : Souvagya Biswas
language : en
Publisher:
Release Date : 2016

Asymmetric Catalysis Of Carbon Carbon Bond Forming Reactions written by Souvagya Biswas and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.

Nature has established numerous methods for synthesis of complex molecules utilizing simple and abundant resources such as the use of CO2, H2O and N2 using sunlight as a source of energy. Even more impressive are the high chemo-, regio-, and stereoselectivites observed in these transformations with a wide variety of both prochiral and chiral substrates. However, methods for the enantioselective incorporation of feedstock materials such as CO, HCN, CO2 or simple alkenes into prochiral molecules are limited and remain an important challenge in the field. The hydrovinylation reaction (HV), where ethylene is added across a carbon-carbon double bond, has been known for nearly fifty years, starting with the works of Hata, Alderson and Wilke. During the past few years, through an approach that relied mostly on mechanistic insights and systematic examination of ligand effects, our group discovered a number of protocols for Ni(II)- and Co(II)-catalyzed enantioselective hydrovinylation (HV) reactions of vinylarenes, 1,3-dienes and strained olefins. While the Ni(II)-catalyzed hydrovinylation (HV) reaction is one of the most selective asymmetric catalyzed carbon-carbon bond forming reactions, its use has been limited to alkenes conjugated to an aromatic ring and strained alkenes. We recently found Co(II)-bisphosphine complexes show much improved regioselectivity with broader functional group compatibility in 1,3-dienes. By utilizing finely tuned catalysts derived from Co(II)-bisphosphine complexes and Me3Al or methylaluminoxane (MAO) acyclic (E) and (Z)-1,3-dienes were found to undergo efficient hydrovinylation giving mostly 1,4-hydrovinylation products in an atmosphere of ethylene. In order to expand the hydrovinylation chemistry, we turned our attention to one of the mostly widely used intermediates on organic chemistry, viz., silyl enol ethers. Trialkylsilyl enol ethers are exceptionally versatile intermediates often used as enolate surrogates for the synthesis of carbonyl compounds. Yet there are no reports of broadly applicable, catalytic methods for the synthesis of chiral silyl enol ethers carrying latent functionalities useful for synthetic operations beyond the many possible reactions of the enol ether moiety itself. The work presented herein reports a general procedure for highly catalytic (substrate : catalyst ratio up to 1000:1) and enantioselective (96% to 98% major enantiomer) synthesis of silyl enol ethers bearing a vinyl group at a chiral carbon at the beta-position. The reactions, run under ambient conditions, use trialkylsiloxy-1,3-dienes and ethylene (1 atmosphere) as precursors, and readily available (bis-phosphine)-cobalt(II) complexes as catalysts. Once we have established the HV reaction conditions of the siloxydienes, we turn our attention towards diastereoselective functionalization of the hydrovinylated products. Under optimized conditions, we are able to successfully utilize our 1,4-hydrovinylated products as reactive nucleophilic synthons for several electrophilic reactions keeping moderate to good diastereomeric ratios. The silyl enolates can be readily converted into novel enantiopure vinyl triflates, a class of highly versatile cross-coupling reagents, enabling the syntheses of other enantiomerically pure trisubstituted alkene intermediates not easily accessible by current methods.

Asymmetric Catalysis Of Carbon Carbon Bond Forming Reactions Through Hydrogen Bonding

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Author : Vijaya Bhasker Gondi
language : en
Publisher:
Release Date : 2008

Asymmetric Catalysis Of Carbon Carbon Bond Forming Reactions Through Hydrogen Bonding written by Vijaya Bhasker Gondi and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with Asymmetric synthesis categories.

Sustainable And Cost Effective Development Of Chiral Metal Catalysts For C H And C X Bond Forming Reactions

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Author : Carlota Borràs Noguera
language : en
Publisher:
Release Date : 2018

Sustainable And Cost Effective Development Of Chiral Metal Catalysts For C H And C X Bond Forming Reactions written by Carlota Borràs Noguera and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.

L'obtenció de compostos enantiomèricament purs ha esdevingut una necessitat que ha conduit a un important progrés en la catàlisi asimètrica, principalment usant compostos organometàl·lics quirals. Entre les diferents estratègies en l'optimització dels catal·litzadors per aconseguir elevades selectivitats i activitats, el disseny i correcta selecció de lligands quirals, modificant-ne les seves propietats és fonamental i la més utilitzada. Que un lligand sigui fàcil de sintetitzar a partir de compostos de partida accessibles i que aquests lligands siguin estables i fàcils de manipular, tenen un elevat interès en la industria. En aquest context, el principal objectiu d'aquesta tesi és la síntesi de diferents famílies de lligands quirals, acomplint els requisits prèviament esmentats, i la seva posterior aplicació a diverses reaccions asimètriques d'elevat interès industrial: hidrogenació d'olefines funcionalitzades i no funcionalitzades catalitzada per Rh i Ir, hidrogenació de cetones catalitzada per Ir, reaccions de substitució al·lílica catalitzades per Pd i reaccions de substitució propargílica catalitzada per Cu. S'han sintetitzat diverses famílies fosfit/fosfinit-tioèter/selenoèter, carbè-tioèter, amino-fosfit/fosfinit/fosfina, i varies famílies de lligands tridentats.

Synthesis And Application Of New Chiral Peptides Guanidines And Formamides As Organocatalysts For Asymmetric C C Bond Formation Reactions

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Author : Sunil Jagtap
language : en
Publisher:
Release Date : 2006

Synthesis And Application Of New Chiral Peptides Guanidines And Formamides As Organocatalysts For Asymmetric C C Bond Formation Reactions written by Sunil Jagtap and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.

Catalytic Asymmetric Carbon Carbon Bond Forming Reactions And Synthesis

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Author : Sha Lou
language : en
Publisher:
Release Date : 2008

Catalytic Asymmetric Carbon Carbon Bond Forming Reactions And Synthesis written by Sha Lou and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008 with categories.

The Development Of Chiral Catalysts For Asymmetric Reactions

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Author : Michael John Rodig
language : en
Publisher:
Release Date : 2011

The Development Of Chiral Catalysts For Asymmetric Reactions written by Michael John Rodig and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.

ABSTRACT: The body of this work is focused on the development of new chiral catalysts for asymmetric reactions. Chiral catalysts can provide an atom economical route to a variety of synthetically important chiral molecules including compounds of biological and pharmacological interest to novel materials with superior structural properties. The efficiency of a chiral catalyst can be measured in both its ability to accelerate a reaction and to promote a highly selective reaction pathway, yielding reaction products with a high degree of optical purity. In many cases, these two criteria are best met when two or more reaction partners are cooperatively activated and organized by a single catalytic species. The latter portion of this work is focused on the development of transition metal catalysts designed to self-assemble in solution to yield multimetallic catalysts capable of activating multiple reaction partners. The first portion is focused on the application of novel, chelating nitrogen donor ligands synthesized en route to N-heterocyclic carbene ligands.