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Homogeneous asymmetric catalysis offers reliable results and the possibility to 'tune' the catalysis on a rational basis. A pitfall, however, is that the separation of the catalyst from the starting material and products is difficult and often results in the loss of the catalytic material. Immobilization offers a potential solution for the user of enantioselective catalysts in industrial processes and laboratories. Heterogeneous catalysis allows continuous operations, recycling of the catalyst, and an easy separation of the reaction products, reducing both waste and costs. Chemists in academia and industry will welcome this careful selection of topics in this handbook that provides readers with practical and detailed information about the technical requirements for the immobilization of chiral catalysts, their application in synthesis, and methods for recycling.
A comprehensive resource on techniques and applications for immobilizing catalysts Catalyst Immobilization: Methods and Applications covers catalyst immobilization topics including technologies, materials, characterization, chemical activity, and recyclability. The book also presents innovative applications for supported catalysts, such as flow chemistry and machine-assisted organic synthesis. Written by an international panel of expert contributors, this book outlines the general principles of catalyst immobilization and explores different types of supports employed in catalyst heterogenization. The book?s chapters examine the immobilization of chiral organocatalysts, reactions in flow reactors, 3D printed devices for catalytic systems, and more. Catalyst Immobilization offers a modern vision and a broad and critical view of this exciting field. This important book: -Offers a guide to supported and therefore recyclable catalysts, which is one of the most important tools for developing a highly sustainable chemistry -Presents various immobilization techniques and applications -Explores new trends, such as 3D printed devices for catalytic systems -Contains information from a leading international team of authors Written for catalytic chemists, organic chemists, process engineers, biochemists, surface chemists, materials scientists, analytical chemists, Catalyst Immobilization: Methods and Applications presents the latest developments and includes a review of the innovative trends such as flow chemistry, reactions in microreactors, and beyond.
This volume provides a comprehensive overview of the rapidly developing field of asymmetric synthesis. Using easy to understand graphical abstracts it presents 348 important catalytic and stoichiometric reactions leading to the synthesis of optically active chiral compounds. The first part of the book covers reactions related to reductions, oxidations, carbon-carbon bond formation and carbon-heteroatom bond formation. Each graphical abstract is accompanied by a list of important keywords and references to assist the reader. The second part concentrates on experimental aspects, describing synthetic procedures for selected chiral reagents and chiral auxiliaries, and provides an invaluable reference tool for laboratory work. Written with both the graduate student and professional organic chemist in mind, this book will serve as an important resource for the synthetic organic chemist.
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.
This book provides the reader with an illustrative overview concerning successful and widely used applications of organocatalysis in the field of natural product synthesis. The main focus will be on organocatalytic key-steps for each (multi-step) synthesis described, whereas other often particularly innovative transformations will be omitted, as this would be beyond the scope of this volume.
Enantioselective synthetic methods are not only in the forefront of chemical and pharmaceutical research but activity in this area is constantly increasing. It is stimulated by the urgency to obtain drugs or compounds of medicinal interest as single anantiomers, and the keeness to synthesize natural products in nonracemic form. This volume presents seven chapters from pioneers and authorities in this rapidly expanding field.
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.
Organocatalyzed Reactions I and II presents a timely summary of organocatalysed reactions including: a) Enantioselective C-C bond formation processes e.g. Michael-addition, Mannich-reaction, Hydrocyanation (Strecker-reaction), aldol reaction, allylation, cycloadditions, aza-Diels-Alder reactions, benzoin condensation, Stetter reaction, conjugative Umpolung, asymmetric Friedel-Crafts reactions; b) Asymmetric enantioselective reduction processes e.g. Reductive amination of aldehydes or ketones, asymmetric transfer hydrogenation; c) Asymmetric enantioselective oxidation processes; d) Asymmetric epoxidation, Bayer-Villiger oxidation; e) Enantioselective a-functionalization; f) A-alkylation of ketones, a-halogenation and a-oxidation of carbonyl compounds.
Stoichiometric asymmetric synthesis is widely used in the academic and industrial sectors for the synthesis of chiral molecules of biological importance. Although catalytic asymmetric synthesis is an alternative, the use of equimolar amounts of chirality provides high selectivities over a wider range of substrates, without extensive modifications of reaction conditions. This volume provides, at postgraduate student level, an accessible introduction to stoichiometric asymmetric synthesis. The authors focus on stereoselective C-C bond formation in acyclic systems, with an emphasis on the use of chiral auxiliaries and reagents. The book is extensively references and so provides a convenient point of entry to the research literature.
This book, unique in its field, is a comprehensive description of all the methodologies reported for carrying out conjugate addition reactions in a stereoselective way, using small chiral organic molecules as catalysts (organocatalysts). In the last 3-4 years, this has been a rapidly growing field in organic chemistry, and many papers have appeared reporting excellent protocols for carrying out these highly efficient transformations that compete well with other classical approaches using transition metal catalysts. A particularly attractive feature of this transformation relies upon the fact that the conjugate addition (Michael and Hetero-Michael reactions) is an extraordinarily effective means to initiate cascade processes which result in the formation of complex molecules from very small and simple starting blocks. The book, written by noted experts, covers all recent advances in this hot topic, and provides a good state-of-the-art review for organic chemists working in this field and all those who wish to start projects in this area.