P Stereogenic Ligands In Enantioselective Catalysis
DOWNLOAD
Download P Stereogenic Ligands In Enantioselective Catalysis PDF/ePub or read online books in Mobi eBooks. Click Download or Read Online button to get P Stereogenic Ligands In Enantioselective Catalysis book now. This website allows unlimited access to, at the time of writing, more than 1.5 million titles, including hundreds of thousands of titles in various foreign languages. If the content not found or just blank you must refresh this page
P Stereogenic Ligands In Enantioselective Catalysis
DOWNLOAD
Author : Arnald Grabulosa
language : en
Publisher: Royal Society of Chemistry
Release Date : 2011
P Stereogenic Ligands In Enantioselective Catalysis written by Arnald Grabulosa and has been published by Royal Society of Chemistry this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with Science categories.
P-stereogenic ligands were among the first to be used in asymmetric catalysis but synthetic difficulties and prejudices have hampered their development. However, continuous screening for new chiral ligands means that they can no longer be ignored and this rigorous reference source reflects their renaissance.The book is filled with many examples from recent primary literature. The synthetic chemist will easily be able to follow the preparation methods which are accompanied by a description of the challenges and limitations. Those working in homogenous catalysis, and wanting to increase their repertoire of ligands, will be able to establish which have already been used in each reaction and their performance.This book provides comprehensive coverage of the application of P-stereogenic ligands in homogeneous catalysis. It begins with a brief chapter on generalities of P-stereogenic compounds: history, configurational stability, and interconversions among them.The book then goes on to describe the main preparative methods, from resolution of racemates to enantioselective catalysis, before focusing on the catalytic applications of P-stereogenic ligands. Chapter 7 describes the use of the ligands in catalytic hydrogenation and related reactions whereas chapter 8 deals with other reactions, mainly C-C bond forming reactions. The aim of these two final chapters is to give an outline of the usefulness of the ligands in homogeneous catalysis.
The Synthesis And Application Of Bulky S Stereogenic And P Stereogenic Chiral Ligands
DOWNLOAD
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.
P Stereogenic Ligands With The Tert Butylmethylphosphine Fragment Coordination Chemistry And Catalysis Of Their Organometallic Complexes
DOWNLOAD
Author : Albert Gallen Ortiz
language : en
Publisher:
Release Date : 2019
P Stereogenic Ligands With The Tert Butylmethylphosphine Fragment Coordination Chemistry And Catalysis Of Their Organometallic Complexes written by Albert Gallen Ortiz and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
The Thesis deals with the preparation, coordination chemistry and use in asymmetric homogeneous catalysis of several optically pure P-stereogenic ligands containing a tert-butylmethylphosphino fragment. In the first part a highly stereoselective synthesis of the Secondary Phosphine Oxide (SPO) tert-butylmethylphosphine oxide is presented. Despite its simplicity, the stereoselective synthesis of this SPO had not been described in the literature. It is known that SPOs present a tautomeric equilibrium between the air-stable pentavalent form (phosphine oxide) and the trivalent form (phosphinous acid), usually completely shifted towards the pentavalent form but that can be displaced towards the phosphinous acid form by metal complexation. In the Thesis the complexation of the mentioned oxide towards Ru, Rh, Ir, Ni, Pd and Au has been explored, yielding a variety of coordination and organometallic compounds, with several coordination modes of the ligand. Some asymmetric catalytic applications of these species have also been studied, giving good conversions but low enantioselectivities. In the second part of the Thesis, the C1-symmetric P-stereogenic ligand MaxPhos has been coordinated to [MCp*Cl] (M = Rh and Ir) and [Ru(p-cymene)Cl] fragments, yielding cationic M-stereogenic organometallic compounds as tetrafluoroborate or hexafluorophosphate salts. Interestingly, in all cases a single stereoisomer has been formed, as confirmed by NMR and X-ray crystallography. This has been rationalised by steric grounds. For Ir, the abstraction of the remaining chloride ligand by silver salts produced a diastereoselective C–H activation of a tert-butyl group of the ligand. The complexes have been used in transfer hydrogenation giving good activities but no enantioselectivities. Finally the third part of the Thesis is devoted to the cyclometallation of [Ir(MaxPHOX)COD]BArF complexes (MaxPHOX stands for a type of P,N phosphinooxazoline ligand recently described by our group having three stereogenic centres) by several ligands under hydrogen atmosphere. It has been found that cyclometallated Ir(III)-hydrido complexes are formed, which are very stable and have been characterised thoroughly. They have been used in asymmetric hydrogenation of N-alkylimines, giving in general complete conversions and very high enantioselectivities (up to 96% ee) for these substrates, which rank among the best described to date. The mechanism of the reaction has been studied and the stereochemical outcome rationalised by means of DFT-based computational methods.
P Stereogenic Ligands In Rhodium And Ruthenium Catalyzed Asymmetric Hydrogenation
DOWNLOAD
Author : Francesca Anna Maienza
language : en
Publisher:
Release Date : 2001
P Stereogenic Ligands In Rhodium And Ruthenium Catalyzed Asymmetric Hydrogenation written by Francesca Anna Maienza and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2001 with categories.
Development Of Transition Metal Catalyzed Methods For The Enantioselective Synthesis Of P Stereogenic Phosphines
DOWNLOAD
Author : Vincent Sai Ho Chan
language : en
Publisher:
Release Date : 2008
Development Of Transition Metal Catalyzed Methods For The Enantioselective Synthesis Of P Stereogenic Phosphines written by Vincent Sai Ho Chan 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.
Fundamentals Of Asymmetric Catalysis
DOWNLOAD
Author : Patrick J. Walsh
language : en
Publisher: University Science Books
Release Date : 2009-01-02
Fundamentals Of Asymmetric Catalysis written by Patrick J. Walsh and has been published by University Science Books this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009-01-02 with Science categories.
This work describes the essential aspects of enantioselective catalysis, with chapters organised by concept rather than by reaction type. Each concept is supported by examples to give the reader broad exposure to a wide range of catalysts, reactions and reaction mechanisms.
The Pauson Khand Reaction
DOWNLOAD
Author : Ramon Rios Torres
language : en
Publisher: John Wiley & Sons
Release Date : 2012-03-01
The Pauson Khand Reaction written by Ramon Rios Torres 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 2012-03-01 with Science categories.
The Pauson-Khand reaction is an important reaction in the field of organic chemistry. It involves the transition-metal catalysed cycloaddition of an alkyne, an alkene and carbon monoxide, to produce cyclopentenones. The importance of this reaction originates from its high value in transforming simple components into the synthetically useful cyclopentenone unit, in which a high degree of molecular complexity can be achieved in a single step, with impressive stereochemical and regiochemical control. The Pauson-Khand Reaction investigates the nature and many variations of this reaction. Topics covered include: the mechanisms of Pauson‐Khand-type reactions non chiral intramolecular and intermolecular versions of Pauson‐Khand reactions asymmetric Pauson‐Khand reaction using chiral auxiliaries the enantioselective Pauson‐Khand reaction Pauson‐Khand reactions catalysed by metals other than cobalt unconventional Pauson‐Khand reactions the Pauson‐Khand reaction in total synthesis Presenting a comprehensive overview of this fundamental reaction, The Pauson-Khand Reaction will find a place on the bookshelves of any organic or organometallic chemist.
Axially Chiral P N Ligands And Their Applications In Asymmetric Catalysis
DOWNLOAD
Author : Alexander Doran
language : en
Publisher:
Release Date : 2019
Axially Chiral P N Ligands And Their Applications In Asymmetric Catalysis written by Alexander Doran and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with categories.
The Synthesis Of Chiral P N Ligands And Their Applications In Asymmetric Catalysis
DOWNLOAD
Author : Cian Reid
language : en
Publisher:
Release Date : 2023
The Synthesis Of Chiral P N Ligands And Their Applications In Asymmetric Catalysis written by Cian Reid and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023 with categories.
Novel Chiral Wide Bite Angle Ligands For Asymmetric Catalysis
DOWNLOAD
Author : Christine Fee Czauderna
language : en
Publisher:
Release Date : 2013
Novel Chiral Wide Bite Angle Ligands For Asymmetric Catalysis written by Christine Fee Czauderna and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Chirality categories.
Achiral wide bite angle ligands have been shown to be highly active and to induce excellent chemo- and regioselectivities in many homogeneously catalyzed reactions. However, only a few examples of chiral wide bite angle ligands are known so far. A diphenyl ether backbone was selected to allow maximum synthetic versatility and potential for a modular approach to design and synthesize such chiral diphosphorus ligands. Three synthetic strategies have been explored in this thesis: i) introduction of chiral substituents in the ligand backbone, ii) the use of P-stereogenic donor atoms and iii) the synthesis of chiral mixed-donor ligands bearing chiral auxiliary groups on the phosphorus atoms. Functionalization of the 3,3'-positions of 2,2'-bis(diphenylphosphino)diphenyl ether by carboxylic acid or ether auxiliaries was achieved via straightforward four-step routes to generate a library of ligands that were tested in various catalytic reactions. In the Pd-catalyzed asymmetric allylic alkylation of l,3-diphenyl-2-propenyl acetate and cyclohexyl-2-enyl acetate with dimethyl malonate the enantioselectivity was found to depend on the size of the chiral auxiliary introduced within the diphenyl ether backbone and its proximity to the phosphorus donor groups and hence to the active metal centre. Two types of mixed donor bidentate diphosphorus ligands based on the diphenylether backbone have been established, i.e. phosphine-phosphite and phosphine-phosphonite derivatives. A small ligand library bearing different chiral auxiliaries was accomplished via straightforward syntheses that enable derivatization of the respective phosphite and phosphonite moieties in the final step. In the Rh-catalysed hydrogenation of several benchmark substrates high conversion and moderate to high enantioselectivities (up to 97% for dimethyl itaconate) were obtained. The enantioselectivity was influenced by the size of the ortho-substituent on the chiral auxiliary group of the phosphite or phosphonite fragment. Two modular synthetic approaches for the preparation of novel wide bite angle diphosphine ligands containing stereogenic P-atoms have been developed. Both protocols involved diphenylether as backbone and the chiral ephedrine based precursor (2R[subscript(P)],4S[subscript(C)],5R[subscript(C)])-oxazaphospholidine borane as initial auxiliary to induce chirality at phosphorus. Various novel diphosphines were isolated as highly enantioenriched compounds with dr-ratios up to 95:5.