Author: D. Gangani NiyadurupolaPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Chiral Auxiliaries and Substrate-directable Reactions in Asymmetric Synthesis
Author: D. Gangani NiyadurupolaChiral Auxiliaries and Substrate Directable Reactions to Access Highly Functionalised Chiral Lactones
Author: Iwan Rhydian DaviesPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
This thesis describes the development of chiral auxiliary based methodologies for the asymmetric synthesis of hydroxylated!-lactones and "--Lactones containing multiple contiguous stereocentres. The first chapter introduces the concept of chirality and provides a general overview of the range of strategies available for the preparation of chiral molecules in enantiomerically pure forms. The second chapter critically reviews the range of synthetic methodology that is currently available for the asymmetric synthesis of chiral #-lactones that are either natural products or useful chiral building blocks for synthesis. The third chapter describes the development of novel methodology for the epoxidation/lactonisation of a range of #x1C;-vinyl-syn-aldols to directly afford!-lactones containing up to four contiguous stereocentres in high de. These reactions were shown to proceed via a mechanism whereby hydroxyl-directed diastereoselective epoxidation is followed by intramolecular attack of their!-acyl-oxazolidin-2- one fragment, to directly afford the desired chiral!-lactone. The?self-cleavage? aspect of these reactions was exploited to enable this methodology to be transferred to polymer-support using an immobilised Evans?-oxazolidin-2-one for asymmetric synthesis. Chapter 4 describes the development of a complementary methodology for the asymmetric synthesis of this type of hydroxylated!-lactone based on a strategy involving dihydroxylation of N-acyl-oxazolidin-2-one-#x1C;-vinyl-syn-aldols using catalytic amounts of osmium tetroxide. This methodology was developed as part of a reinvestigation of previously reported dihydroxylation reactions by Dias and coworkers, where we have clearly shown that the stereochemistry of thelactones reported in their paper have been incorrectly assigned. This diastereoselective dihydroxylation methodology has been successfully applied to the asymmetric synthesis of the natural product deoxyribonolactone. Finally, Chapter 5 describes the development of methodology for the asymmetric synthesis of chiral "-lactones containing four contiguous stereocentres of use as potential chiral building blocks for the synthesis of polyketide natural products. In this approach, cyclopropanation of N-acyl-oxazolidin-2-one-#x1C;-vinyl-syn-aldols occurs under the sterodirecting effect of the #x1C;- hydroxyl group to afford cyclopropyl-aldols in very high de. These cyclopropyl-aldols are then ring opened in the presence of mercuric ions, with their N-acyl-oxazolidin-2-one fragment acting as an internal nucleophile, to afford highly functionalised alkyl-mercury species that may be subsequently reduced to afford their corresponding "-lactones in high de.
Principles of Asymmetric Synthesis
Author: R.E. GawleyPublisher: Elsevier
ISBN: 0080514774
Category : Science
Languages : en
Pages : 395
Book Description
The world is chiral. Most of the molecules in it are chiral, and asymmetric synthesis is an important means by which enantiopure chiral molecules may be obtained for study and sale. Using examples from the literature of asymmetric synthesis (more than 1300 references), the aim of this book is to present a detailed analysis of the factors that govern stereoselectivity in organic reactions. It is important to note that the references were each individually checked by the authors to verify relevance to the topics under discussion. The study of stereoselectivity has evolved from issues of diastereoselectivity, through auxiliary-based methods for the synthesis of enantiomerically pure compounds (diastereoselectivity followed by separation and auxiliary cleavage), to asymmetric catalysis. In the latter instance, enantiomers (not diastereomers) are the products, and highly selective reactions and modern purification techniques allow preparation - in a single step - of chiral substances in 99% ee for many reaction types. After an explanation of the basic physical-organic principles of stereoselectivity, the authors provide a detailed, annotated glossary of stereochemical terms. A chapter on "Analytical Methods" provides a critical overview of the most common methods for analysis of stereoisomers. The authors then follow the 'tried-and-true' format of grouping the material by reaction type. Thus, there are four chapters on carbon-carbon bond forming reactions (enolate alkylations, organometal additions to carbonyls, aldol and Michael reactions, and cycloadditions and rearrangements), one chapter on reductions and hydroborations (carbon-hydrogen bond forming reactions), and one on oxidations (carbon-oxygen and carbon-nitrogen bond forming reactions). Leading references are provided to natural product synthesis that have been accomplished using a given reaction as a key step. In addition to tables of examples that show high selectivity, a transition state analysis is presented to explain - to the current level of understanding - the stereoselectivity of each reaction. In one case (Cram's rule) the evolution of the current theory is detailed from its first tentative (1952) postulate to the current Felkin-Anh-Heathcock formalism. For other reactions, only the currently accepted rationale is presented. Examination of these rationales also exposes the weaknesses of current theories, in that they cannot always explain the experimental observations. These shortcomings provide a challenge for future mechanistic investigations.
Principles of Asymmetric Synthesis
Author: Robert E. GawleyPublisher: Elsevier
ISBN: 0080914136
Category : Science
Languages : en
Pages : 569
Book Description
The world is chiral. Most of the molecules in it are chiral, and asymmetric synthesis is an important means by which enantiopure chiral molecules may be obtained for study and sale. Using examples from the literature of asymmetric synthesis, this book presents a detailed analysis of the factors that govern stereoselectivity in organic reactions. After an explanation of the basic physical-organic principles governing stereoselective reactions, the authors provide a detailed, annotated glossary of stereochemical terms. A chapter on "Practical Aspects of Asymmetric Synthesis" provides a critical overview of the most common methods for the preparation of enantiomerically pure compounds, techniques for analysis of stereoisomers using chromatographic, spectroscopic, and chiroptical methods. The authors then present an overview of the most important methods in contemporary asymmetric synthesis organized by reaction type. Thus, there are four chapters on carbon-carbon bond forming reactions, one chapter on reductions, and one on oxidations (carbon-oxygen and carbon-nitrogen bond forming reactions). This organization allows the reader to compare the leading methods for asymmetric synthesis in an appropriate context. A highlight of the book is the presentation and discussion of transition states at the current level of understanding, for important reaction types. In addition, extensive tables of examples are used to give the reader an appreciation for the scope of each reaction. Finally, leading references are provided to natural product synthesis that has been accomplished using a given reaction as a key step. Authoritative glossary to aid understanding of stereochemical terminology Explanations of the key factors influencing stereoselectivity with numerous examples, organized by reaction type A handy reference guide to the literature of asymmetric synthesis for practitioners in the field
Principles and Applications of Asymmetric Synthesis
Author: Guo-Qiang LinPublisher: John Wiley & Sons
ISBN: 0471465240
Category : Science
Languages : en
Pages : 536
Book Description
Asymmetric synthesis remains a challenge to practicing scientistsas the need for enantiomerically pure or enriched compoundscontinues to increase. Over the last decade, a large amount ofliterature has been published in this field. Principles andApplications of Asymmetric Synthesis consolidates and evaluates themost useful methodologies into a one-volume resource for theconvenience of practicing scientists and students. Authored by internationally renowned scientists in the field, thisreliable reference covers more than 450 reactions and includesimportant stoichiometric as well as catalytic asymmetric reactions.The first chapter reviews the basic principles, commonnomenclature, and analytical methods, and the remainder of the bookis organized according to reaction type. The text examines suchtopics as: Carbon-carbon bond formations involving carbonyls, enamines,imines, and enolates Asymmetric C-O bond formations including epoxidation,dihydroxylation, and aminohydroxylation Asymmetric synthesis using the Diels-Alder reaction and othercyclizations Applications to the total synthesis of natural products Use of enzymes in asymmetric synthesis Practicing chemists in the pharmaceutical, fine chemical, andagricultural professions as well as graduate students will findthat Principles and Applications of Asymmetric Synthesis affordscomprehensive and current coverage.
Chiral Auxiliaries and Ligands in Asymmetric Synthesis
Author: J. Seyden-PennePublisher: Wiley-Interscience
ISBN:
Category : Science
Languages : en
Pages : 744
Book Description
Table of Contents Preface Abbreviations Introduction 1 1 Enantiomerically Pure Chiral Auxiliaries 43 2 Chiral Reagents 87 3 Chiral Catalysis and Catalysts Bearing Chiral Ligands 117 4 Asymmetric Deprotonations and Protonations 143 5 Alkylations and Related Reactions 157 6 Additions to C=O and C=N Double Bonds 209 7 Additions to Carbon-Carbon Double Bonds 367 8 Additions to Double Bonds Bearing Heteroatoms. Oxidations of Sulfides and Selenides 503 9 Cycloadditions 513 10 Sigmatropic Rearrangements 593 11 Transition Metal Catalyzed Reactions 619 References 637 Index 707.
Asymmetric Synthesis V3
Author: James MorrisonPublisher: Elsevier
ISBN: 0323145000
Category : Science
Languages : en
Pages : 593
Book Description
Asymmetric Synthesis, Volume 3: Stereodifferentiating Addition Reactions, Part B presents intensive investigations in leading academic and industrial laboratories on stereodifferentiating addition reactions. This book is divided into eight chapters and begins with a comprehensive review of the formation of chiral metal enolates and their stereoselective alkylation reactions. These topics are followed by discussions on chiral Aldol addition reactions and the many variations of asymmetric synthesis that may be carried out using chiral oxazolines. A chapter describes the alkylation of chiral hydrazones, a process that yields chiral-substituted aldehydes and ketones. Other chapters explore a variety of cyclization processes that form carbon-carbon and carbon-heteroatom bonds. The last chapters deal with the asymmetric cycloadditions and sigma-tropic rearrangements. Synthetic chemists and researchers will find this book invaluable.
Chiral Building Blocks in Asymmetric Synthesis
Author: Jacek WojaczynskiPublisher: John Wiley & Sons
ISBN: 3527834192
Category : Science
Languages : en
Pages : 692
Book Description
Chiral Building Blocks in Asymmetric Synthesis A comprehensive introduction to the important classes of chiral building blocks Chirality — the asymmetric quality found in certain chemical compounds — plays an essential role in our world: chiral compounds can be found in biology, pharmaceutical compounds, agrochemicals, and fragrances. The stereoselective preparation of these complex molecular constructions constitutes a challenge. To this end, modern asymmetric synthesis utilizes a variety of valuable and efficient reagents employed as chiral auxiliaries, metal complexes and organocatalysts in stereoselective catalysis, and enantiopure reactants termed as chiral building blocks. In Chiral Building Blocks in Asymmetric Synthesis, the achievements in the fields of preparation of and applications of chiral blocks are presented. In doing so, the book comprehensively discusses the important classes of these reactants as the key for the asymmetric synthesis of chiral molecules. As such, it is an indispensable resource about synthetic methods, as well as possible modifications and transformations of important classes of chiral compounds. It also highlights the importance of their use as reactants and auxiliaries in the preparation of more sophisticated molecules or supramolecular systems. In Chiral Building Blocks in Asymmetric Synthesis readers will also find: Organization according to the most important compound classes — e.g. amino acids, BINOL and its derivatives, terpenes, and others — with an emphasis on synthesis and application A focus on the use of chiral building blocks for the preparation of bioactive compounds and supramolecular assemblies Chiral Building Blocks in Asymmetric Synthesis is a useful reference for organic chemists, catalytic chemists, chemists in industry, medicinal chemists, pharmaceutical chemists, and the libraries that support them.
Asymmetric Synthesis of Three-Membered Rings
Author: Hélène PellissierPublisher: John Wiley & Sons
ISBN: 3527802037
Category : Science
Languages : en
Pages : 800
Book Description
The first handbook to focus on the asymmetric synthesis of different types of three-membered rings. The outstanding and experienced authors have an excellent international reputation and cover cyclopropanes, epoxides and aziridines as well as chiral oxaziridines in equal measure. To this end, they describe in detail different synthetic approaches starting with chiral substrates as well as the application of chiral metal- or organocatalysts. Furthermore, methods for the kinetic resolution of initially racemic products are treated alongside recent advances and novel developments in established techniques for the synthesis of three-membered rings. With its structured composition this is of high interest to scientists in methodological and natural product synthesis as well as those in industrial and pharmaceutical chemistry.
Chiral Reagents for Asymmetric Synthesis
Author: Leo A. PaquettePublisher: John Wiley & Sons
ISBN: 9780470856253
Category : Science
Languages : en
Pages : 618
Book Description
Derived from the renowned, Encyclopedia of Reagents for Organic Synthesis (EROS), the related editors have created a new handbook which focuses on chiral reagents used in asymmetric synthesis and is designed for the chemist at the bench. This new handbook follows the same format as the Encyclopedia, including an introduction and an alphabetical arrangement of the reagents. As chiral reagents are the key for the successful asymmetric synthesis, choosing the right reagents is essential, in this handy reference the editors give details on how to prepare, store and use the reagents as well as providing key reactions to demonstrate where reagents have been successfully used. Comprehensive information on 226 reagents Covers 64 reagents which were not included in EROS All information in one easy to use volume – at an affordable price All reagents included will be added to e-EROS – please visit the site where you can gain access to over 50,000 reactions and 3,800 of the most frequently consulted reagents. Visit: www.interscience.wiley.com/eros