Exploratory Research Into Atypical N-heterocyclic Carbenes

Exploratory Research Into Atypical N-heterocyclic Carbenes
Author:
Publisher:
Total Pages: 127
Release: 2013
Genre: Electronic books
ISBN:

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The objective of this research is to create unique and highly functional N-heterocyclic carbene complexes that provide maximum catalytic features in close proximity to the metal centers. The N-heterocyclic carbenes created over the past 20 years have generally consisted of imidazole moieties substituted at both nitrogen atoms with alkyl and aryl substitutents. These typical N-heterocylic carbenes have presented many highly stable and tunable complexes used in catalysis, however, some beneficial features would be imparted on these N-heterocyclic carbenes if one of the alkyl and aryl substituted sites were allowed to remain un-substituted. These unique atypical protic N-heterocyclic carbenes allow for acid base chemistry to occur in close proximity to the metal center while simultaneously providing the tunable, highly sigma-donating features of a typical N-heterocyclic carbene. The research presented in this thesis explores the synthetic approach to atypical protic N-heterocyclic carbene ligand precursors as well as their complexation and subsequent catalytic capabilities. Two ligand precursor families were created: one consisting of an iodobenzene moiety attached to a tert-butyl imidazole group, and one in which a pyridine ring moiety is attached to a tert-butyl imidazole group. The iodobenzene group yielded two ligand precursors, 2a and 2b, both containing methylene spacers between the auxiliary moiety and tert-butyl groups. The pyridine-containing family consisted of 3a, where the tert-butyl imidazole was directly attached to the pyridine ring, and 3c, where the tert-butyl imidazole was attached to the ring by a methylene spacer. Attempts to complex the first ligand precursor family 2a and 2b were unsuccessful and lead to the synthesis of the pyridine analogues 3a and 3c which were successfully complexed to both iridium and rhodium metal centers yielding: Ir-Phos- 3a, Ir-Phos-3c, Ir-S0-3a, Ir-S1-3c, Rh-S0-3a, and Rh-S1-3c. Catalytic studies carried out with the six complexes above consisted of the oxidation of alcohols to their corresponding ketones. These catalytic tests revealed a higher degree of successful turnover with the 3c containing complexes. Crystallographic data suggests that bond angles and bond distances found in 3c containing complexes give inherent advantages to the 3c containing complexes due to the flex allowed by the methylene spacer. Additionally, catalytic comparisons of methylated analogues of 3c with the atypical protic 3c complexes showed a decrease in catalytic activity suggesting that the presences of the un-substituted nitrogen in close proximity to the metal center yields the predicted benefit of using atypical protic N-heterocyclic carbenes.

N-heterocyclic Carbenes

N-heterocyclic Carbenes
Author: Silvia Díez-González
Publisher: Royal Society of Chemistry
Total Pages: 469
Release: 2011
Genre: Science
ISBN: 1849730423

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Over the last fifteen years, N-heterocyclic carbenes (NHCs) have mostly been used as ancillary ligands for the preparation of transition metal-based catalysts. Compared to phosphorus-containing ligands, NHCs tend to bind more strongly to metal centres, avoiding the necessity for the use of excess ligand in catalytic reactions. The corresponding complexes are often less sensitive to air and moisture, and have proven remarkably resistant to oxidation. Recent developments in catalysis applications have been facilitated by the availability of carbenes stable enough to be bottled, particularly for their use as organocatalysts. This book shows how N-heterocyclic carbenes can be useful in various fields of chemistry and not merely laboratory curiosities or simple phosphine mimics. NHCs are best known for their contribution to ruthenium and palladium-catalysed reactions but the scope of this book is much broader. The synthesis of NHC ligands and their corresponding metal complexes are covered in depth. Moreover, the biological activity of NHC-containing complexes, as well as an overview of their theoretical aspects are included. Such metal species are further examined, not only in terms of their catalytic applications, but also of their stereoelectronic parameters and reactivity/stability. Finally, special attention is given to the hot topic of organocatalysis. The book will be of interest to postgraduates, academic researchers and those working in industry.

N-Heterocyclic Carbenes in Organocatalysis

N-Heterocyclic Carbenes in Organocatalysis
Author: Akkattu T. Biju
Publisher: John Wiley & Sons
Total Pages: 556
Release: 2019-03-04
Genre: Science
ISBN: 3527809074

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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.

The Organometallic Chemistry of N-heterocyclic Carbenes

The Organometallic Chemistry of N-heterocyclic Carbenes
Author: Han Vinh Huynh
Publisher: John Wiley & Sons
Total Pages: 352
Release: 2017-01-23
Genre: Science
ISBN: 1118698800

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The Organometallic Chemistry of N-heterocyclic Carbenes describes various aspects of N-heterocyclic Carbenes (NHCs) and their transition metal complexes at an entry level suitable for advanced undergraduate students and above. The book starts with a historical overview on the quest for carbenes and their complexes. Subsequently, unique properties, reactivities and nomenclature of the four classical NHCs derived from imidazoline, imidazole, benzimidazole and 1,2,4-triazole are elaborated. General and historically relevant synthetic aspects for NHCs, their precursors and complexes are then explained. The book continues with coverage on the preparation and characteristics of selected NHC complexes containing the most common metals in this area, i.e. Ni, Pd, Pt, Ag, Cu, Au, Ru, Rh and Ir. The book concludes with an overview and outlook on the development of various non-classical NHCs beyond the four classical types. Topics covered include: Stabilization, dimerization and decomposition of NHCs Stereoelectronic properties of NHCs and their evaluation Diversity of NHCs Isomers of NHC complexes and their identification NMR spectroscopic signatures of NHC complexes normal, abnormal and mesoionic NHCs The Organometallic Chemistry of N-heterocyclic Carbenes is an essential resource for all students and researchers interested in this increasingly important and popular field of research.

N-Heterocyclic Carbenes

N-Heterocyclic Carbenes
Author: Steven P. Nolan
Publisher: Wiley-VCH
Total Pages: 0
Release: 2014-11-03
Genre: Science
ISBN: 9783527334902

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This comprehensive reference and handbook covers in depth all major aspects of the use of N-heterocyclic carbene-complexes in organic synthesis: from the theoretical background to characterization, and from cross-coupling reactions to olefin metathesis. Edited by a leader and experienced scientist in the field of homogeneous catalysis and use of NHCs, this is an essential tool for every academic and industrial synthetic chemist.

2-Oxoglutarate-Dependent Oxygenases

2-Oxoglutarate-Dependent Oxygenases
Author: Christopher J Schofield
Publisher: Royal Society of Chemistry
Total Pages: 508
Release: 2015-05-06
Genre: Science
ISBN: 1849739501

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Since the discovery of the first examples of 2-oxoglutarate-dependent oxygenase-catalysed reactions in the 1960s, a remarkably broad diversity of alternate reactions and substrates has been revealed, and extensive advances have been achieved in our understanding of the structures and catalytic mechanisms. These enzymes are important agrochemical targets and are being pursued as therapeutic targets for a wide range of diseases including cancer and anemia. This book provides a central source of information that summarizes the key features of the essential group of 2-oxoglutarate-dependent dioxygenases and related enzymes. Given the numerous recent advances and biomedical interest in the field, this book aims to unite the latest research for those already working in the field as well as to provide an introduction for those newly approaching the topic, and for those interested in translating the basic science into medicinal and agricultural benefits. The book begins with four broad chapters that highlight critical aspects, including an overview of possible catalytic reactions, structures and mechanisms. The following seventeen chapters focus on carefully selected topics, each written by leading experts in the area. Readers will find explanations of rapidly evolving research, from the chemistry of isopenicillin N synthase to the oxidation mechanism of 5-methylcytosine in DNA by ten-eleven-translocase oxygenases.

Modern Catalytic Methods for Organic Synthesis with Diazo Compounds

Modern Catalytic Methods for Organic Synthesis with Diazo Compounds
Author: Michael P. Doyle
Publisher: Wiley-Interscience
Total Pages: 680
Release: 1998-01-19
Genre: Science
ISBN:

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This much-needed resource brings together a wealth of procedures for the synthesis and practical use of diazocarbonyl compounds. It features methods for the preparation of important catalysts and for applications of diazocarbonyl compounds within each of the main transformation categories-including in-depth coverage of cyclopropanation, C-H and X-H insertion, Wolff rearrangement, ylide formation, aromatic cycloaddition and substitution, and many other useful reactions. Written by leading experts in the field, this book contains cutting-edge material on highly enantioselective transformations, and presents new ways of thinking about diazocarbonyl compounds and their applications, from donor-acceptor cyclopropanes in organic synthesis to macrocyclic cyclopropanation. Complete with illustrative examples of procedures in each chapter, clear diagrams, and a detailed bibliography, this practical reference gives readers the tools they need to put diazocarbonyl compounds to work for their own projects-an invaluable source of guidance for synthetic organic chemists, chemical scientists, and advanced students.

Contemporary Drug Synthesis

Contemporary Drug Synthesis
Author: Jie Jack Li
Publisher: John Wiley & Sons
Total Pages: 238
Release: 2004-12-27
Genre: Science
ISBN: 0471686735

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An integrated and insightful look at successful drug synthesis in today's drug discovery market The pharmaceutical industry is unquestionably vibrant today, with drug synthesis making a vital contribution. Whether in the early developmental stages of identifying and optimizing a lead, or the latter stages of process development and cost-effective scale-up, the ability to design elegant and economical synthetic routes is often a major factor in the eventual viability and commercial success of a drug. Contemporary Drug Synthesis examines how leading researchers and manufacturers have integrated chemistry, biology, pharmacokinetics, and a host of other disciplines in the creation and development of leading drugs. Authored by four of the pharmaceutical industry's most respected scientists, this timely volume: Focuses on the processes that resulted in high-profile drugs including Lipitor, Celebrex, Viagra, Gleevec, Nexium, Claritin, and over a dozen others Provides an in-depth introduction to each drug, followed by a detailed account of its synthesis Organizes the drugs into fourteen therapeutic areas for clarity and ease of use Process chemists provide an essential bridge between chemistry and the marketplace, creating scientifically practical drug processes while never losing sight of the commercial viability of those processes. Contemporary Drug Synthesis meets the needs of a growing community of researchers in pharmaceutical research and development, and is both a useful guide for practicing pharmaceutical scientists and an excellent text for medicinal and organic chemistry students.

Site-Selective Catalysis

Site-Selective Catalysis
Author: Takeo Kawabata
Publisher: Springer
Total Pages: 237
Release: 2016-02-23
Genre: Science
ISBN: 3319263331

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The series Topics in Current Chemistry presents critical reviews of the present and future trends in modern chemical research. The scope of coverage is all areas of chemical science including the interfaces with related disciplines such as biology, medicine and materials science.The goal of each thematic volume is to give the non-specialist reader, whether in academia or industry, a comprehensive insight into an area where new research is emerging which is of interest to a larger scientific audience.Each review within the volume critically surveys one aspect of that topic and places it within the context of the volume as a whole. The most significant developments of the last 5 to 10 years are presented using selected examples to illustrate the principles discussed. The coverage is not intended to be an exhaustive summary of the field or include large quantities of data, but should rather be conceptual, concentrating on the methodological thinking that will allow the non-specialist reader to understand the information presented. Contributions also offer an outlook on potential future developments in the field.Review articles for the individual volumes are invited by the volume editors.Readership: research chemists at universities or in industry, graduate students

Industrial Biocatalysis

Industrial Biocatalysis
Author: Peter Grunwald
Publisher: CRC Press
Total Pages: 1201
Release: 2014-12-11
Genre: Medical
ISBN: 9814463892

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Biocatalysis has become an essential tool in the chemical industry and is the core of industrial biotechnology, also known as white biotechnology, making use of biocatalysts in terms of enzymes or whole cells in chemical processes as an alternative to chemical catalysts. This shift can be seen in the many areas of daily life where biocatalysts-with