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My work on computing complex catalyzed organic transformations reveals that only a few subtle chemical factors, e.g. non-classical hydrogen bonding, (hyper)conjugation and steric effects, common across different catalyst manifolds are critical for catalysis and selectivity. Rational manipulation and exploitation of these factors has led to improved catalyst designs, which has previously been an oft-promised but rarely delivered endeavor. Hydrogen bonding is critical to stabilizing structures in both the ground and transition state across many branches of chemistry and life. C-H bonds polarized through either hybridization or proximity to a developing or full positive charge can provide stabilization through interaction with negatively charged atoms in a C-H···O non-classical hydrogen bond (NCHB). In the transition state, where a molecule experiences temporarily amplified polarization, these hydrogen bonds can serve to stabilize the structures and differentiate between diastereomeric TSs A joint experimental and computational investigation on a diaryl prolinol silyl ether-catalyzed Michael cascade reaction to complex furanyl/pyranyl products uncovered the synergistic relationship between catalyst and substrate beyond the basic enamine activation and steric control. NCHBs were discovered to stabilize the transiently polar transition state. The kinetic resolution of addition products was afforded by virtue of the conformation of the substrate preventing or allowing hyperconjugation. An N-heterocyclic carbene-catalyzed dynamic kinetic resolution of [beta]-ketoesters was discovered to display an unusual resolution mechanism. Rapid substrate epimerization early in the aldol mechanism allowed routing through the lowest energy diastereomeric pathway, which also differs in mechanism from the other diastereomeric TSs. Facial control arises from the presence or absence of a single chiral NCHB donor stabilizing the developing alkoxide. Diastereocontrol is afforded by the configuration of the epimerizable [beta]-stereocenter hydrogen affecting the conjugative ability of the keto aryl group. This same control arises in the rapid and enantioselective retro-[2+2] decarboxylations of the product bicyclic [beta]-lactones to cyclopentenes. A study on the origins of enantioselectivity of an NHC-catalyzed homoaldol with acylphosphonates uncovered stereodifferentiating pockets of NCHB akin to an oxyanion hole between the catalyst aryl groups and the phosphonyl (P=O) oxygen. Computations predicted an increase of selectivity by blocking the sites stabilizing the minor transition state. Synthesis and test of the catalyst verified computational predictions. A chiral bifunctional aminothiourea has been developed for the Michael addition of acrylates to [alpha]-ketones to generate asymmetric all-carbon quaternary centers. This catalyst both activates the nucleophile via enamine catalysis and employs hydrogen bonding catalysis to activate the carbonyl-bearing electrophile. A joint experimental and computational study reveals the mechanism of this process and seeks to uncover the origins of selectivity. Computations predict that deletion of the catalyst [beta]-phenyl group would increase selectivity; however, experimental synthesis and test led to unforeseen catalyst decomposition.
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.
Asymmetric Organocatalysis Comprehensive resource on the latest and most important developments in the highly vivid field of asymmetric organocatalysis The book provides a comprehensive overview of the most important advancements in the field of asymmetric organocatalysis that have occurred within the last decade. It presents valuable examples of newly developed synthetic methodologies based on various organocatalytic activation modes. Special emphasis is given to strategies where organocatalysis is expanding its potential by pushing the boundaries and founding new synergistic interactions with other fields of synthetic chemistry, such as metal catalysis, photocatalysis, and biocatalysis. The application of different concepts (such as vinylogy, dearomatization, or cascade reactivity), resulting in the development of new functionalization strategies, is also discussed. Sample topics covered within the book include: New developments in enantioselective Brønsted acid catalysis with strong hydrogen-bond donors Asymmetric phase-transfer catalysis, from classical applications to new concepts Halogen-bonding organocatalysis Asymmetric electrochemical organocatalysis and synergistic organo-organocatalysis Immobilized organocatalysts for enantioselective continuous flow processes Mechanochemistry and high-pressure techniques in asymmetric organocatalysis Useful tools in elucidation of organocatalytic reaction mechanisms With an overall focus on new reactions and catalysts, this two-volume work is an indispensable source for everyone working in the field of asymmetric organocatalysis.
The Series is intended to provide an accessible reference for postgraduates and industrialists working in the field of catalysis and its applications. Books will be produced either as monographs or reference handbooks. The Series will cover research developments and applications of catalysis, in both academia and industry. --Résumé de l'éditeur.
Explore the latest advances involving organo/metal combined catalysts from leading contributors in the field In Asymmetric Organo-Metal Catalysis: Concepts, Principles, and Applications, accomplished chemist Liu-Zhu Gong delivers a comprehensive discussion of how to design efficient organo/metal combined catalyst systems, new cooperatively catalyzed asymmetric reactions, relay catalytic cascades, and multicomponent reactions. The distinguished author covers critical topics, like the combined catalysis of chiral phase transfer catalysts, enamine, iminium, nucleophilic Lewis base, or Bronsted acids with metal complexes, while also covering the cooperative catalysis of photocatalysts and organocatalysts. The book offers readers an exploration of the general concepts and principles of bond activation and reorganization, together with a comprehensive introduction to the historical developments and recent advances in the field. Readers will also benefit from the descriptions of new chemistry and new synthetic methods included within. Asymmetric Organo-Metal Catalysis also provides: Thorough introductions to chiral PTC-metal cooperative catalysis and enamine-metal cooperative catalysis Comprehensive explorations of iminum-metal relay catalysis and cooperative catalysis of bronsted acids and transition metals Practical discussions of metal-bronsted acid relay catalysis and Lewis base–Lewis acid cooperative catalysis In-depth examinations of Lewis base-transition metal cooperative catalysis and photocatalysis combined with organocatalysis Perfect for organic, catalytic, and pharmaceutical chemists, Asymmetric Organo-Metal Catalysis: Concepts, Principles, and Applications is also an invaluable resource for chemists working with or on organometallics.
The rate of advance in areas of science is seldom constant. Usually certain fields effloresce with activity because of the ~ealization that solutions are possible to long standing important problems. So it is now with asymmetric catalysis, a field which promises to change profoundly the strategic thinking of synthetic chemists. As this Report will show, reagents which can induce catalytic enantiocontrol of chemical transformations could represent the ultimate synthetic method. Nearly all synthetic strategies of complex molecules involve steps which require enantiocontrol and, in many cases, a specific catalytic transformation embodying enan tiocontrol has enormous advantages in terms of the rate and economy of the reaction. Because asymmetric catalysis is in a formative stage, workers with different backgrounds have joined the field. This Workshop had representatives with organometallic, organic, structural, kinetic, enzymatic, microbiological and industrial backgrounds. Each had his own perspective and this Report represents a consensus of this group of eleven people. The result is probably as compre hensive and balanced a view of the subject as is possible at present. It is hoped that those who have until now had but a glancing interest in asymmetric catalysis will find this Report a useful indication of its present state. We believe that asymmetric catalysis will have an increasing impact on the development of chemistry and will eventually dominate much of synthetic and industrial chemistry.
Catalytic Asymmetric Synthesis Seminal text presenting detailed accounts of the most important catalytic asymmetric reactions known today This book covers the preparation of enantiomerically pure or enriched chemical compounds by use of chiral catalyst molecules. While reviewing the most important catalytic methods for asymmetric organic synthesis, this book highlights the most important and recent developments in catalytic asymmetric synthesis. Edited by two well-qualified experts, sample topics covered in the work include: Metal catalysis, organocatalysis, photoredox catalysis, enzyme catalysis C–H bond functionalization reactions Carbon–carbon bond formation reactions, carbon–halogen bond formation reactions, hydrogenations, polymerizations, flow reactions Axially chiral compounds Retaining the best of its predecessors but now thoroughly up to date with the important and recent developments in catalytic asymmetric synthesis, the 4th edition of Catalytic Asymmetric Synthesis serves as an excellent desktop reference and text for researchers and students, from upper-level undergraduates all the way to experienced professionals in industry or academia.
Summarizing the emerging field of N-heterocyclic carbenes used in organocatalysis, this is an excellent overview of the synthesis and applications of NHCs focusing on carbon-carbon and carbon-heteroatom bond formation. Alongside comprehensive coverage of the synthesis, characteristics and applications, this handbook and ready reference also includes chapters on NHCs for polymerization reactions and natural product synthesis.
This book presents a comprehensive review of the methods and approaches being adopted to push forward the boundaries of computational catalysis.
In this reference leaders at the forefront of research provide an insight into one of the hottest topics in organic synthesis, focusing on the most important enantioselective reactions. Clearly structured, each entry begins with a concise introduction, including a mechanistic discussion of the reaction, followed by preparative guidelines for newcomers, such as carefully selected working procedures with critical notes for bench chemists, rules of thumb and tips and tricks.