Design Synthesis And Characterization Of New Chiral Ligands And Mechanistic Investigations Into Catalytic Enantioselective Hydrogenation Reactions
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Design Synthesis And Characterization Of New Chiral Ligands And Mechanistic Investigations Into Catalytic Enantioselective Hydrogenation Reactions
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Author :
language : en
Publisher:
Release Date : 2000
Design Synthesis And Characterization Of New Chiral Ligands And Mechanistic Investigations Into Catalytic Enantioselective Hydrogenation Reactions written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000 with categories.
Development Of Effective Chiral Ligands For Catalytic Asymmetric Hydrogenation
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Author : Weicheng Zhang
language : en
Publisher:
Release Date : 2009
Development Of Effective Chiral Ligands For Catalytic Asymmetric Hydrogenation written by Weicheng Zhang and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
Chiral Ligands
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Author : Montserrat Diéguez
language : en
Publisher: CRC Press
Release Date : 2021
Chiral Ligands written by Montserrat Diéguez and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with Medical categories.
Many new drugs on the market are chiral compounds, that is, they can exist in two non-superimposable mirror-image forms. Asymmetric catalysis encompasses a large variety of processes for obtaining such compounds.
Chiral Ferrocenes In Asymmetric Catalysis
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Author : Li-Xin Dai
language : en
Publisher: John Wiley & Sons
Release Date : 2010-02-01
Chiral Ferrocenes In Asymmetric Catalysis written by Li-Xin Dai and has been published by John Wiley & Sons this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010-02-01 with Science categories.
This book meets the long-felt need for a reference on ferrocenes with the focus on catalysis. It provides a thorough overview of the synthesis and characterization of different types of chiral ferrocene ligands, their application to various catalytic asymmetric reactions, and versatile chiral materials as well as drug intermediates synthesized from them. Written by the "who's who" of ferrocene catalysis, this is a guide to the design of new ferrocene ligands and synthesis of chiral synthetic intermediates, and will thus be useful for organic, catalytic and synthetic chemists working in academia, industrial research or process development.
Metal Catalyzed Asymmetric Hydrogenation Evolution And Prospect
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Author :
language : en
Publisher: Academic Press
Release Date : 2021-11-23
Metal Catalyzed Asymmetric Hydrogenation Evolution And Prospect written by and has been published by Academic Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-11-23 with Science categories.
Metal-Catalyzed Asymmetric Hydrogenation, Volume 68 in the Advances in Catalysis series, fills the gap between journal papers and textbooks across diverse areas of catalysis research. For more than 60 years, this series has recorded and presented the latest progress in the field of catalysis, giving the scientific community comprehensive and authoritative reviews. Chapters in this new release include Asymmetric hydrogenation of functionalized olefins, Asymmetric hydrogenation of unfunctionalized olefins or with poorly coordinative groups, Asymmetric hydrogenation of imines, Asymmetric hydrogenation of ketones, Asymmetric hydrogenation in industry, and Computational insights into metal-catalyzed asymmetric hydrogenation. This series is an invaluable and comprehensive resource for chemical engineers and chemists working in the field of catalysis in both academia and industry, with this release focusing on solid acids, surface acidity and heterogeneous acid catalysis. Contains authoritative reviews written by experts in the field Explores topics that reflect progress in the field, such as catalyst synthesis, catalyst characterization, catalytic chemistry, reaction engineering, computational chemistry and physics Provides insightful and critical articles that are fully edited to suit various backgrounds
Cobalt Catalyzed Asymmetric Hydrogenation Of Alkenes
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Author : Hongyu Zhong
language : en
Publisher:
Release Date : 2021
Cobalt Catalyzed Asymmetric Hydrogenation Of Alkenes written by Hongyu Zhong and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021 with categories.
Transition metal-catalyzed hydrogenation reactions represent one of the cornerstones in homogeneous catalysis. The asymmetric hydrogenation of unsaturated molecules is an atom-economical method for the synthesis of enantio-enriched compounds and is of particular interest to the pharmaceutical, agrochemical and fine chemical industries. Catalysts based on second- and third-row transition metals, including rhodium, iridium and ruthenium, have been intensively studied in the past five decades and applied widely in industries. Thorough mechanistic studies have been carried out, facilitating catalyst designs and process optimizations. There has been a growing interest in developing relatively Earth abundant, 3d transition metal hydrogenation catalysts based on manganese, iron, cobalt and nickel as alternatives to 4d and 5d transition metals owing to their reduced cost, uninterrupted supply chains and relatively lower toxicity. First-row metals have kinetically and thermodynamically accessible oxidation states separated by one-electrons, which offers opportunities for catalyst designs with new reaction mechanisms. Despite recent progress, the understandings of catalyst speciation upon in situ activation are still limited. Elucidating the coordination chemistry, oxidation states and spin states of active catalysts is of fundamental importance to inform catalyst designs and improve the catalytic performance of first-row metals.In this dissertation, the synthesis, characterization and mechanistic studies of a host of cobalt catalysts for the asymmetric hydrogenation of carbon?carbon double bonds will be introduced. In particular, cobalt catalysts supported by chiral bidentate phosphine ligands have been identified as a ?privileged? class of catalysts and will be the focus of this dissertation.The cobalt-catalyzed asymmetric hydrogenation affording the epilepsy medication, levetiracetam, has been developed and applied to a 200-gram, pilot scale hydrogenation. The unique stability and high activity of reduced cobalt catalysts in protic solvents represent major advances for first-row alkene hydrogenation catalysts. The reaction mechanisms of enamide asymmetric hydrogenation with the formally cobalt(0) catalysts were investigated by experimental and computational methods. The enantioselectivity originates from the different reactivity of a pair of diastereomeric bis(phosphine)cobalt(0)?enamide complexes with H2. The cobalt-catalyzed asymmetric hydrogenation of ?, ?-unsaturated carboxylic acids with unusual homolytic H2 cleavage has been achieved, affording chiral acid products including Naproxen, Flurbiprofen and an L-DOPA precursor. The reactions between bis(phosphine)cobalt(II) dialkyl precatalysts and alcohols have been investigated and the bis(phosphine)Co(II) alkoxide products remained catalytically active. A cobalt-promoted methanol dehydrogenation reaction was also studied. The long-sought-after cobalt analogs of Schrock-Osborn type rhodium catalysts have been synthesized and characterized. A cationic bis(phosphine)cobalt(I) arene catalyst was discovered to be highly active for the asymmetric hydrogenation affording the type 2 diabetes medication, Sitagliptin. The ligand substitution of bis(phosphine)cobalt(0)(diene) catalysts was investigated using kinetic methods establishing a dissociative substitution mechanism. Solid state parameters and electronic structure studies imply their alternative assignment as bis(phosphine)cobalt(II) metallacyclopropane, providing a rationale for the unique protic stability. A family of cobalt precatalysts supported by the bis(phosphine), (R,R)-BenzP*, has been synthesized and characterized. The magnetic properties of dimeric bis(phosphine)Co(I)monochloride precatalysts have also been elucidated.
Enantioselection In Asymmetric Catalysis
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Author : Ilya D. Gridnev
language : en
Publisher: CRC Press
Release Date : 2016-11-03
Enantioselection In Asymmetric Catalysis written by Ilya D. Gridnev and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-11-03 with Science categories.
The field of asymmetric catalysis is currently one of the hottest areas in chemistry. This unique book focuses on the mechanism of enantioselectivity in asymmetric catalysis, rather than asymmetric catalysis from the synthetic view. It describes reliable, experimentally and computationally supported mechanisms, and discusses the danger of so-called "plausible" or "accepted" mechanisms leading to wrong conclusions. It draws parallels to enzymatic catalysis in biochemistry, and examines in detail the physico-chemical aspects of enantioselective catalysis.
Synthesis Of New Chiral Ligands And Their Application In Catalytic Enantioselective Reactions
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Author : Kedar Shankar Karmarkar
language : en
Publisher:
Release Date : 1996
Synthesis Of New Chiral Ligands And Their Application In Catalytic Enantioselective Reactions written by Kedar Shankar Karmarkar and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996 with categories.
The Synthesis And Application Of Bulky S Stereogenic And P Stereogenic Chiral Ligands
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Author : Seán Doran
language : en
Publisher:
Release Date : 2012
The Synthesis And Application Of Bulky S Stereogenic And P Stereogenic Chiral Ligands written by Seán Doran 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.
This doctoral thesis was focused on the design and synthesis of novel chiral ligands for application in asymmetric catalysis. One of the best examples of asymmetric catalysis is the asymmetric hydrogenation reaction for its atom economy, ease of access to both S and R enantiomers and almost ultimate enantiomeric excess obtainable in a multitude of substrates. There has been much investigation into this reaction and there has been a plethora of chiral ligands designed which catalyze this reaction in high enantiomeric excess using metals such as rhodium, iridium and ruthenium. The vast majority of these ligands are diphosphines with their chirality lying either on the backbone of the ligand or on the coordinating phosphorus atom itself. In the beginning of this work investigation was undertook to explore the possibility of successfully employing a new type of ligand class in the asymmetric hydrogenation reaction, namely the N-phosphino sulfinamide or PNSO ligands. PNSO ligands had been successfully applied to the asymmetric Pauson-Khand reaction in the Riera group yielding cyclopentenone Pauson-Khand adducts in high yield and very high enantioselectivity. The family of PNSO ligands prepared in the Riera group was attractive because apart from the high yields and enantioselectivities obtained from the reactions in which they were used, they proved to be easily prepared in short syntheses from commercially available starting materials. It was believed if they could be successfully applied in asymmetric hydrogenation for their ease of preparation they would be an attractive alternative to the diphosphine ligand class. Unfortunately the first two PNSO-Rh complexes successfully prepared provided low enantioselectivities and difficulties were encountered while trying to prepare further analogues. After some time trying to achieve PNSO-Rh complex analogues unsuccessfully the direction of the project was shifted away from the N-phosphino sulfinamide ligand class in asymmetric hydrogenation. The MaxPhos ligand had recently been developed in the group and had proven highly promising. A study was demanded of its substrate scope as applied in rhodium catalyzed asymmetric hydrogenation. Substrates already described in the literature were prepared and the asymmetric hydrogenation of them catalyzed by the MaxPhos-Rh precatalyst was performed and conditions to do so were optimized. Of seven substrates prepared the MaxPhos-Rh proved to hydrogenate five of those with high enantioselectivity. The TOF of the MaxPhos rhodium catalyst applied in the hydrogenation of the Z-MAC substrate was examined by monitoring the flux of hydrogen and was calculated at 0.065 s-1. MaxPhos complexes of cobalt and palladium were prepared to form part of the investigation into widening the reaction scope of the ligand. [(MaxPhos)Co2(CO)4(C2H2)] proved to catalyze the Pauson-Khand reaction of norbornadiene and 1-hexyne with 24 % yield and 28 %, a noteworthy enantiomeric excess for the catalytic asymmetric Pauson-Khand reaction. Chalcogenated derivatives of MaxPhos were prepared. The diselenide was used to explore the electronic nature of the ligand. The MaxPhos-rhodium carbonyl stretching was examined. MaxPhos-BH3 was used to prepare mono-chalcogenated MaxPhos derivatives. They were applied also in asymmetric hydrogenation once complexed to rhodium but enantiomeric excess of no more than 21 % was obtained in the hydrogenation of the substrate Z-MAC. The aminophosphine, a chiral building block and key intermediate in the preparation of the MaxPhos ligand, was used in the attempt to prepare bulky chiral amidine ligands and although two such species were prepared they proved inapplicable in asymmetric catalysis.
Design Synthesis And Evaluation Of Chiral Nonracemic Ligands And Catalysts For Asymmetric Synthesis
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Author : Michael P. A. Lyle
language : en
Publisher:
Release Date : 2005
Design Synthesis And Evaluation Of Chiral Nonracemic Ligands And Catalysts For Asymmetric Synthesis written by Michael P. A. Lyle and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with Asymmetric synthesis categories.
The work described in this thesis concerns the design, synthesis and evaluation of new chiral nonracemic ligands and catalysts for use in asymmetric reactions. A series of chiral nonracemic chloroacetals were prepared from 2-chloro-4- methyl-6,7-dihydro-5H-[l]pyrindine-7-one and a variety of C2-symmetric and chiral nonracemic 1,2-ethanediols (R = Me, i-Pr and Ph). These chloroacetals were further elaborated, in a modular fashion, to provide a series of chiral ligands and catalysts. A new class of C2-symmetric 2,2'-bipyridyl ligands were prepared in one step fiom the chloroacetals via a nickel(0)-mediated homo-coupling reaction. These ligands were then evaluated as chiral directors in copper@)-catalyzed asymmetric cyclopropanation reactions of styrene and diazoesters (up to 44% ee). A chiral pyridine N-oxide and a C2-symmetric 2,2'-bipyridyl N, N'-dioxide were also prepared by direct oxidation of the corresponding pyridine and the 2,2'-bipyridine, respectively. These chiral N-oxides were evaluated as chiral catalysts in desymmeterization reactions of cis-stilbene oxide (up to 20% ee). A series of pyridylphosphine ligands (P, N-ligands) were subsequently prepared in two steps from the chloroacetals via a Suzuki coupling reaction with orthofluorophenylboronic and on subsequent displacement of the fluoride with the potassium anion of diphenylphosphine. These ligands were then evaluated in palladium-catalyzed asymmetric allylic substitution reactions of racemic 3-acetoxy-l,3-diphenyl-1-propene with dimethyl malonate. Optimization of the reaction conditions resulted in the formation of the alkylated product in excellent yield (91%) and in high enantiomeric excess (90%). A related chiral nonracemic and C2-symmetric 2,2'-bipyridyl ligand was prepared from 2-chloro-4-methyl-5H-[llpyrindine. This pyrindine was prepared from a common intermediate that was used in the synthesis of the first generation of ligands. The chirality of this second generation ligand was installed by a Sharpless asymmetric dihydroxylation reaction (90% ee). The subsequently elaborated 2,2'-bipyridyl ligand (enriched to>99% ee) was then evaluated in copper(1)-catalyzed asymmetric cyclopropanation reactions of alkenes and diazoesters. In the case of the reaction of para-fluorostyrene and tert-butyl diazoacetate, the corresponding cyclopropane was formed in good diastereoselectivity (92:8) and in excellent enantioselectivity (99% ee). This ligand was also evaluated in copper(I1)-catalyzed asymmetric Friedel-Crafts alkylation reactions of various substituted indoles (up to 90% ee) and in copper(1)- catalyzed asymmetric allylic oxidation reactions of cyclic alkenes with tert-butyl peroxybenzoate (up to 9 1 % ee).