Mechanistic Insights and Functionalization of Alkynes in Homogeneous Gold Catalysis PDF Download
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Author: Manish Kumar
Publisher:
ISBN:
Category : Catalysts
Languages : en
Pages : 185
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Book Description
The focus of my dissertation work was to study the basic mechanistic insights of gold-catalyzed reactions. Although the various mechanistic pathways of gold catalysis are better understood nowadays, numerous questions still remain unanswered concerning the nature of deactivation of the catalyst's active species, high resistance towards protodeauration, and how we can solve these problems to improve the efficiency of gold catalysis. To address these challenges in gold catalysis we conducted first a detailed experimental study to understand the mechanism of deactivation of gold active species. Based on the combination of experimental data, we proposed that gold disproportionation is preferred as compared to reduction of the active gold catalyst. To address the high resistance toward protodeauration, we explored a new strategy to enhance the efficacy of gold-catalyzed reactions through hydrogen-bonding assisted protodeauration using additives chosen for their pKBHX (hydrogen-bond basicity). To address the threshold phenomenon, we observed that high gold affinity impurities (halides, bases) in solvents, starting materials, filtration or drying agents could affect the reactivity of the gold catalyst adversely, which, in turn, may significantly reduce the TON of cationic gold. Use of a suitable acid activator (e.g. HOTf, In(OTf)3) reactivates the gold catalyst and makes the reaction proceed smoothly at low gold catalyst loading. To explore the reactivity of Au catalysts towards oxygen-atom transfer reactions, we investigated the gold-catalyzed addition of O-nucleophiles to alkynes and found that this reaction can produce synthetically important vinyl ether products in excellent yields and regioselectivities at room temperature. At higher temperature, 3,3-sigmatropic rearrangement of vinyl ether products gives access to highly functionalized benzotriazoles.
Author: Manish Kumar
Publisher:
ISBN:
Category : Catalysts
Languages : en
Pages : 185
Get Book Here
Book Description
The focus of my dissertation work was to study the basic mechanistic insights of gold-catalyzed reactions. Although the various mechanistic pathways of gold catalysis are better understood nowadays, numerous questions still remain unanswered concerning the nature of deactivation of the catalyst's active species, high resistance towards protodeauration, and how we can solve these problems to improve the efficiency of gold catalysis. To address these challenges in gold catalysis we conducted first a detailed experimental study to understand the mechanism of deactivation of gold active species. Based on the combination of experimental data, we proposed that gold disproportionation is preferred as compared to reduction of the active gold catalyst. To address the high resistance toward protodeauration, we explored a new strategy to enhance the efficacy of gold-catalyzed reactions through hydrogen-bonding assisted protodeauration using additives chosen for their pKBHX (hydrogen-bond basicity). To address the threshold phenomenon, we observed that high gold affinity impurities (halides, bases) in solvents, starting materials, filtration or drying agents could affect the reactivity of the gold catalyst adversely, which, in turn, may significantly reduce the TON of cationic gold. Use of a suitable acid activator (e.g. HOTf, In(OTf)3) reactivates the gold catalyst and makes the reaction proceed smoothly at low gold catalyst loading. To explore the reactivity of Au catalysts towards oxygen-atom transfer reactions, we investigated the gold-catalyzed addition of O-nucleophiles to alkynes and found that this reaction can produce synthetically important vinyl ether products in excellent yields and regioselectivities at room temperature. At higher temperature, 3,3-sigmatropic rearrangement of vinyl ether products gives access to highly functionalized benzotriazoles.
Author: Zhi Xiang Wong
Publisher:
ISBN:
Category : Alkenes
Languages : en
Pages : 129
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Book Description
Author: Veronique Michelet
Publisher: World Scientific
ISBN: 1783265558
Category : Science
Languages : en
Pages : 564
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Book Description
Research on designing new catalytic systems has been one of the most important fields in modern organic chemistry. One reason for this is the predominant contribution of catalysis to the concepts of atom economy and green chemistry in the 21st century. Gold, considered catalytically inactive for a long time, is now a fascinating partner of modern chemistry, as scientists such as Bond, Teles, Haruta, Hutchings, Ito and Hayashi opened new perspectives for the whole synthetic chemist community. This book presents the major advances in homogeneous catalysis, emphasizing the methodologies that create carbon-carbon and carbon-heteroatom bonds, the applications that create diversity and synthesize natural products, and the recent advances and challenges in asymmetric catalysis and computational research.It provides readers with in-depth information about homogeneous gold-catalyzed reactions and presents several explanations for the scientific design of a catalyst. Readers will be able to understand the entire gold area and find solutions to problems in catalysis.Gold Catalysis — An Homogeneous Approach is part of the Catalytic Science Series and features prominent authors who are experts in their respective fields.
Author: Lise Molinari
Publisher:
ISBN:
Category :
Languages : en
Pages : 181
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Book Description
Author: A. Stephen K. Hashmi
Publisher: John Wiley & Sons
ISBN: 3527319522
Category : Science
Languages : en
Pages : 419
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Book Description
With its impressive features, gold has led to completely new reaction types in recent years, which in turn have strongly influenced both organic catalysis and material science. Other fields where a significant amount of new results has been obtained include nanotechnology, self assembly/supramolecular systems and biochemical/medicinal chemistry. As a result, gold is one of the hottest topics in catalysis at the moment, with an increasing amount of research being carried out in this field. While focusing on homogeneous catalysis, this monograph also covers the main applications in heterogeneous catalysis. Following a look at the gold-catalyzed addition of heteroatom nucleophiles to alkynes, it goes on to discuss gold-catalyzed additions to allenes and alkenes, gold-catalyzed benzannulations, cycloisomerization and rearrangement reactions, as well as oxidation and reduction reactions. The whole is finished off with a section on gold-catalyzed aldol and related reactions and the application of gold-catalyzed reactions to natural product synthesis. Of interest to synthetic chemists and inorganic chemists, as well as organic chemists working in homogeneous catalysis, physical and technical chemists.
Author: LeGrande M. Slaughter
Publisher: Springer
ISBN: 3319137220
Category : Science
Languages : en
Pages : 292
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Book Description
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.
Author: Geoffrey C Bond
Publisher: World Scientific
ISBN: 1908979852
Category : Science
Languages : en
Pages : 383
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Book Description
Gold has traditionally been regarded as inactive as a catalytic metal. However, the advent of nanoparticulate gold on high surface area oxide supports has demonstrated its high catalytic activity in many chemical reactions. Gold is active as a heterogeneous catalyst in both gas and liquid phases, and complexes catalyse reactions homogeneously in solution. Many of the reactions being studied will lead to new application areas for catalysis by gold in pollution control, chemical processing, sensors and fuel cell technology. This book describes the properties of gold, the methods for preparing gold catalysts and ways to characterise and use them effectively in reactions. The reaction mechanisms and reasons for the high activities are discussed and the applications for gold catalysis considered./a
Author: Antoine Simonneau
Publisher:
ISBN: 9783319067087
Category :
Languages : en
Pages : 268
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Book Description
Author: Denis Forster
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 354
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Book Description
Author: Yanzhao Wang
Publisher:
ISBN: 9781321203318
Category :
Languages : en
Pages : 285
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Book Description
In the past dozen years, great progress has been made in developing highly efficient homogenous gold catalysis. As soft "pi" Lewis acids, cationic gold(I) complexes are particularly powerful in terms of activating alkyne/allene towards nucleophilic attack, leading to a variety of synthetically versatile structures. During my research, several synthetic methods have been developed, including: (1) Au-catalyzed ligand-directed anti nucleophilic attack of alkynes; the new ligands I developed enable highly efficient gold-catalyzed nucleophilic addition of acids, anilines and water to the alkynes; and catalyst loadings could be lowered to 10 parts per million; (2) rapid access of chroman-3-ones via gold-catalyzed oxidation of propargyl aryl ethers; this step-economic and efficient transformation was realized by a bulky gold catalyst, Me4tBuXPhosAuNTf2 and bulky electron-deficient pyridine N-oxides derived from Hantzsch esters; (3) Au-catalyzed novel indole synthesis via a key [3,3] sigmatropic rearrangement; 2-alkylindoles were produced with high regioselectivity and efficiency from easily accessed N-arylhydroxylamines under mild conditions; an improved approach involved cooperative dual catalysis of Zn and Au was developed; much broader substrate scope, shorter reaction time and good to excellent yields were achieved.
