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The use of abundantly available feedstock such as ethylene, carbon monoxide, hydrogen cyanide, alkyl acrylates, in fine chemical synthesis is a major challenge in organic synthesis, and developing asymmetric versions of reactions which makes use of these feedstock chemicals is an even bigger challenge. The detailed mechanism of a recently discovered cobalt-mediated hydrovinylation of prochiral dienes has been studied. The role of trimethyl aluminum employed as an activator of the cobalt(II)-dihalide complex employed for the cobalt-mediate hydrovinylation has been determined to be: reduction of Co(II)-complex to Co(I)-complex and generation of cationic-Co(I) species as active catalyst. Well defined Co(I)-complexes were synthesized and characterized via NMR spectroscopy and crystallography. Treatment of these Co(I) complexes with various activators such as NaBARF, ZnCl2, B(C6F5)3, generates cationic Co(I) which mediates the reaction. This new protocol for hydrovinylation was successfully employed for a broadly applicable asymmetric heterodimerization of acrylates and 1,3-dienes. The reaction tolerates other functional groups such as olefins, alcohols, alkyl halides, trialkylsiloxy-, and even sensitive silyl enol ethers.
Developments of new catalytic transformations by using earth-abundant metal (base-metal) catalysts have played a significant role in modern civilization and will continue to play a vital role towards maintaining and improving our quality of life. Particularly, these transformations have had a tremendous impacts on the agricultural, transport, energy, and pharmaceutical sectors. This field of base-metal catalysis would enjoy added benefits with the utilization of sustainable feedstock carbon sources for fine chemical synthesis. However, the dual problems of activation of thermodynamically stable precursors (ethylene, CO2, H2, CO, aldehydes, acrylates, HCN) and their highly stereoselective incorporation into other readily available substrates (1,3-dienes, alkynes, enynes) pose new challenges. In a nutshell, the development of benign catalysts for employing sustainable feedstock starting materials has the potential to transform inexpensive materials into valuable precursors for fine chemical synthesis. My dissertation work focuses on the development of scalable, atom-economical, and cost-effective catalytic methods for the preparation of value-added products relevant to fine chemicals. The overarching aims are to use sustainable feedstocks or readily available precursors, and environmentally benign chemistry. To achieve these goals, three efficient catalytic methods have been developed which employ complexes of an earth-abundant metal, cobalt, with ligands derived from naturally occurring amino acids or commercially available bis-phosphine ligands. The key to success was a systematic ligands investigation that inspired the design and synthesis of novel ligands to achieve high chemo-, regio-, and enantioselectivities. In the first methodology, a broadly applicable method affecting [2+2] cycloaddition between several alkynes and alkenyl derivatives to form cyclobutenes has been disclosed. A library of >70 nearly enantiopure cyclobutenes, which are ubiquitous motifs in bioactive compounds, have been synthesized in excellent yields. In the second methodology, ligand controlled regio-divergent enantioselective synthesis of primary and secondary homoallylic boronates (>50 examples) from readily available 1,3-dienes and a common boron reagent have been developed. Furthermore, the hydrofunctionalization of 1,3-dienes program has been extended to unprecedented enantioselective hydroacylation of 1,3-dienes. This method opens a realm to achieve the synthesis of enantiopure alpha- or beta-chiral center containing ketones. In all the mentioned transformations above, cationic Co(I)- species has been invoked as an active catalyst. To further corroborate the role of cationic Co(I)-complexes, a reliable protocol has been developed to synthesize, isolate discrete neutral and cationic Co(I)-complexes and characterized by X-ray crystallography. These isolated cationic complexes serve as an excellent single-component catalyst for heterodimerization, hydroboration, and hydroacylation, suggesting the key role of cationic Co(I)-complexes in these transformations. While developing these efficient methodologies, striking ligand, counterion, and solvent effects have been revealed along with a unique role of a cationic Co(I) intermediate in the reactions which advanced novel fundamental concepts. We believe that these cationic Co(I) complexes have broader utility in homogeneous catalysis. We hope that the rational evolution of a mechanism-based strategy that led to the eventual successful outcome and the attendant support studies will add to the burgeoning organometallic chemistry of cobalt and its applications with further implications beyond the synthetic reactions described in this dissertation.
Assembling organic molecules with contiguous quaternary carbon atoms has long represented a formidable synthetic challenge. Besides a purely academic interest of developing access to topologically complex molecular assemblies, significance of this research area was determined by the presence of said molecular units in natural steroids and their construction via biomimetic polyene cyclization reactions. In this account, we have established that radical coupling reactions of Co2(CO)6-complexed 1,4-enynes occur in a regio- and stereoselective fashion providing access to 3E,7E-decadien-1,9-diynes in excellent yields (84 - 99%). The formation of contiguous quaternary carbon atoms follows a tandem allylic rearrangement that projects an original reaction site gamma to the metal core. Propargyl alcohols with an alpha-alkenyl group as a substituent are treated with HBF4, followed by the reduction of the highly conjugated propargyl cations with zinc. The scope of the reaction is expanded to include 1,4-enyne complexes with cyclic and acyclic substituents gamma to the metal core, as well as aliphatic and aromatic substituents attached to the acetylenic termini. The alternative design includes relocation of the cation generation site – alpha-to-gamma – prior to the reduction step, by employing either the cation isolation technique with HBF4, or an in situ generation of ionic propargyl triflates with Tf2O. Retention of the reaction site in 1,3-enynes is observed in both gamma-alcohols and gamma-Me ethers, affording respective gamma,gamma-radical dimers in excellent yields (98 - 99%). The "reaction-site-projection" strategy can now be applied for gaining access to functionally diverse complex molecules containing, as a central theme, contiguous quaternary carbon atoms, and also for probing an upper limit of projection span in ionic and radical reactions leading to molecular assemblies of a higher level of conjugation. This method is a valuable asset for synthetic organic chemistry, natural product synthesis, and medicinal chemistry since it can be used as a key step in targeted syntheses of organic molecules of practical importance, in lead optimizations, and also in constructing molecular assemblies of higher conjugation.
This comprehensive textbook describes the synthesis, characterization and technical and engineering applications of polymers. Offering a broad and balanced introduction to the basic concepts of macromolecular chemistry and to the synthesis and physical chemistry of polymers, it is the ideal text for graduate students and advanced Masters students starting out in polymer science. Building on the basic principles of organic chemistry and thermodynamics, it provides an easily understandable and highly accessible introduction to the topic. Step by step, readers will obtain a detailed and well-founded understanding of this vibrant and increasingly important subject area at the intersection between chemistry, physics, engineering and the life sciences.Following an approach different from many other textbooks in the field, the authors, with their varying backgrounds (both from academia and industry), offer a new perspective. Starting with a clear and didactic introduction, the book discusses basic terms and sizes and shapes of polymers and macromolecules. There then follow chapters dedicated to polymers in solutions, molar mass determination, and polymers in the solid state, incl. (partially) crystalline or amorphous polymers as well as their application as engineering materials. Based on this information, the authors explain the most important polymerization methods and techniques. Often neglected in other textbooks, there are chapters on technical polymers, functional polymers, elastomers and liquid crystalline polymers, as well as polymers and the environment. An overview of current trends serves to generate further interest in present and future developments in the field.This book is the English translation of the successful German textbook "Polymere", which was awarded the Chemical Industry in Germany’s 2015 literature Prize (“Literaturpreis des Fonds der Chemischen Industrie”) for its innovative, novel approach, and its good accessibility and readability, while at the same time providing comprehensive coverage of the field of polymer science.
Cation Transporters in Plants presents expert information on the major cation transporters, along with developments of various new strategies to cope with the adverse effects of abiotic and biotic stresses. The book will serve as a very important repository for the scientist, researcher, academician and industrialist to enhance their knowledge about cation transport in plants. Further, applications listed in the book will facilitate future developments in crop designing strategies. This comprehensive resource provides an alternative strategy for abiotic and biotic stress management in agricultural and horticultural crops. In addition, it will further improve basic knowledge om the origin and mechanism of cation homeostasis and their role in developmental transition and stress regulation. Contains in-depth knowledge about various cation transporters in plants Provides information about important macro and micronutrient cation transporters and their applications in the agricultural and biotechnology sectors Facilitates agricultural scientists and industries in future crop designing strategies Provides an alternative strategy for abiotic and biotic stress management in agricultural and horticultural crops
The carbonyl group is undoubtedly one of the most important functional groups in organic chemistry, both in its role as reactive center for synthesis or derivatisation and as crucial feature for special structural or physiological properties. Vast and profound progress has been made in all aspects modern carbonyl chemistry. These achievements are, however, rather dispersed in the literature and it is often not easy for the researcher obtain a comprehensive overview of a relevant topic. Modern Carbonyl Chemistry overcomes this inconvenience by collating the information for appropriate themes. In this work internationally renowned experts and leaders in the field have surveyed recent aspects and modern features in carbonyl chemistry, such as cascade-reactions, one-pot-syntheses, recognition, or site differentiation.
Provides a much-needed account of the formidable "cobalt rush" in organic synthesis and catalysis Over the past few decades, cobalt has turned into one of the most promising metals for use in catalytic reactions, with important applications in the efficient and selective synthesis of natural products, pharmaceuticals, and new materials. Cobalt Catalysis in Organic Synthesis: Methods and Reactions provides a unique overview of cobalt-catalysed and -mediated reactions applied in modern organic synthesis. It covers a broad range of homogeneous reactions, like cobalt-catalysed hydrogenation, hydrofunctionalization, cycloaddition reactions, C-H functionalization, as well as radical and biomimetic reactions. First comprehensive book on this rapidly evolving research area Covers a broad range of homogeneous reactions, such as C-H activation, cross-coupling, synthesis of heterocyclic compounds (Pauson-Khand), and more Chapters on low-valent cobalt complexes as catalysts in coupling reactions, and enantioselective cobalt-catalyzed transformations are also included Can be used as a supplementary reader in courses of advanced organic synthesis and organometallic chemistry Cobalt Catalysis in Organic Synthesis is an ideal book for graduates and researchers in academia and industry working in the field of synthetic organic chemistry, catalysis, organometallic chemistry, and natural product synthesis.
Provides a complete and accessible A to Z collection of information on catalysis This updated and enlarged must-have edition of a classic book on catalysis explains the important terms of all aspects of the subject - including biocatalysis, homogeneous catalysis, heterogeneous catalysis - as well as the terms associated with it. It also looks at related topics like spectroscopy or analytical methods. Featuring 20% more content than the previous edition, it comprehensively covers the topic in a clear and concise manner, and includes abbreviations, brief biographic entries of important scientists who have worked in catalysis, trade names, important catalytic processes, named reactions, reactions, and other important keywords in the general field of catalysis. Written by more than 200 top scientists and with more than 15,000 entries on all aspects of catalysis, Catalysis from A to Z: A Concise Encyclopedia, 5th Edition is filled with figures, tables, cross-references, and references. It covers acids, ligands, catalytic reactions in organic synthesis, kinetics and thermodynamics of catalytic reactions, and catalyst labeling. The book also looks at theoretical backgrounds of catalytic reactions, industrial catalytic processes, autoclaves, colloids, nanomaterials, spectroscopically methods for catalyst analysis, and more. Provides all the knowledge scientists need to know about homogeneous, heterogeneous, and biochemical catalysis Includes more than 15,000 keywords in compact entries Newly updated and expanded edition of the bestselling classic Comprehensive, succinct, and easy to use Edited by an experienced team of top editors and authors with contributions from over 200 scientific experts Offers German and French translations of the keywords to help students and non-native English speakers Catalysis from A to Z: A Concise Encyclopedia is an ideal resource for every student, chemist, scientist, and engineer involved in catalytic chemistry, chemical engineering, biochemistry, organic chemistry, and more.
The endothelium, a monolayer of endothelial cells, constitutes the inner cellular lining of the blood vessels (arteries, veins and capillaries) and the lymphatic system, and therefore is in direct contact with the blood/lymph and the circulating cells. The endothelium is a major player in the control of blood fluidity, platelet aggregation and vascular tone, a major actor in the regulation of immunology, inflammation and angiogenesis, and an important metabolizing and an endocrine organ. Endothelial cells controls vascular tone, and thereby blood flow, by synthesizing and releasing relaxing and contracting factors such as nitric oxide, metabolites of arachidonic acid via the cyclooxygenases, lipoxygenases and cytochrome P450 pathways, various peptides (endothelin, urotensin, CNP, adrenomedullin, etc.), adenosine, purines, reactive oxygen species and so on. Additionally, endothelial ectoenzymes are required steps in the generation of vasoactive hormones such as angiotensin II. An endothelial dysfunction linked to an imbalance in the synthesis and/or the release of these various endothelial factors may explain the initiation of cardiovascular pathologies (from hypertension to atherosclerosis) or their development and perpetuation. Table of Contents: Introduction / Multiple Functions of the Endothelial Cells / Calcium Signaling in Vascular Cells and Cell-to-Cell Communications / Endothelium-Dependent Regulation of Vascular Tone / Conclusion / References