Investigations of the Mechanism of a Friedel-Crafts-Like Gold and Silver-Catalyzed Microwave Reaction

Investigations of the Mechanism of a Friedel-Crafts-Like Gold and Silver-Catalyzed Microwave Reaction
Author: Tamara Nader El-Hayek Ewing
Publisher:
Total Pages:
Release: 2021
Genre:
ISBN:

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Within the last 20-40 years, gold catalysis has becoming increasingly more interesting to researchers. A particular turning point was when one group was able to perform several alcohol additions to unactivated alkynes using a gold(I) catalyst. A significant result of this success was the ability to replace toxic mercury (II) catalysts that had been previously used to perform similar transformations. Since this report, others have successfully shown that gold(I) catalysts of the form [L-Au-Cl] as well as gold(III) catalysts in various forms, are able to activate a variety of starting materials for inter and intramolecular transformations. Despite this work, the mechanism of action for gold catalysis remains unknown. There are several complicating factors including relativistic, ligand, solvent and temperature effects, among others. Of particular interest to us are silver effect complications as well as the phenomena of gold decay. Silver salts are typically used in gold catalysis as an activating co-catalyst. The silver salt is presumed to be a halide scavenger in gold(I) catalysis, removing the chloride and exposing the Au+ center. However, several groups have reported on silver and its counter ion playing a less benign role--even demonstrating that silver can catalyze transformations on its own. This at the least warrants further investigation of the nature of silver in the reaction. Gold decay also introduces complications to gold catalysis. One possibility for the explanation for gold decay is through disproportionation of the gold(I) catalyst to gold(0) and gold(III). This is a particularly exciting avenue for exploration in the work done here. In the reaction of interest, 1-phenylethol and 4-methylanisole combine to produce a Friedel-Crafts-like product. In typical Friedel-Crafts reactions, a hard acid like AlCl3 is used to generate a carbocation which then undergoes a nucleophilic addition and C-C bond formation. In our reaction, if the gold(I) catalyst that was utilized initially were to disproportionate, gold(III)--a harder Lewis Acid--would help explain the Friedel-Crafts reactivity and the gold(0) generated would explain the gold-plating on the vials seen after the reaction. Through organic synthesis methods as well as some inorganic analysis, we were able to make some interesting discoveries. First, we see gold(I) decay in the absence of substrate, visually producing black/purple particles. At extended reaction times, the analysis of these particles shows about 33% of the gold we put in by mass was recovered. This still left open the possibility of gold(I) in solution as the active catalyst, however. In fact, when the particles from the substrate-less reaction were filtered out, the filtrate remaining was still able to catalyze the reaction. This did not lead us closer to understanding if gold(I) or gold(III) was the active catalyst but did let us know that the active catalyst remained in solution despite decay. We were also able to confirm that a gold(III) salt can catalyze the reaction of interest, though the yields were less than half of what was accomplished in the optimized gold(I) reaction. Additionally, with low catalyst loadings and significantly reduced reaction times (1 minute), a secondary product was observed in the gold(III)-catalyzed reactions. The nature of this secondary product--whether it is a major/minor product or if it is some intermediate species is still under investigation. Overall, evidence showing that gold(0) is being formed and the ability for a gold(III) salt to form the Friedel-Crafts-like product is clear, but that alone does not fully support disproportionation. Indirect evidence leads us to believe that disproportionation is the mechanism for gold decay, however, without direct evidence of a gold(III) species, we cannot say for sure. Also, there is some support for gold(III) being the active catalyst but there are some necessary questions that still need to be explored. In particular, an investigation of the possible intermediate or secondary product in both gold(I) and gold(III)-catalyzed reactions would be helpful in identifying the mechanistic path for the C-C bond formation in this Friedel-Crafts-like addition.

Asymmetric catalysis

Asymmetric catalysis
Author: Michael P. Doyle
Publisher: JAI Press(NY)
Total Pages: 0
Release: 1997
Genre: Asymmetric synthesis
ISBN: 9780762300686

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This is the second volume in a series covering research advances in the field of catalytic processes.

Artificial Metalloenzymes and MetalloDNAzymes in Catalysis

Artificial Metalloenzymes and MetalloDNAzymes in Catalysis
Author: Montserrat Diéguez
Publisher: John Wiley & Sons
Total Pages: 431
Release: 2018-02-21
Genre: Technology & Engineering
ISBN: 3527804072

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An important reference for researchers in the field of metal-enzyme hybrid catalysis Artificial Metalloenzymes and MetalloDNAzymes in Catalysis offers a comprehensive review of the most current strategies, developed over recent decades, for the design, synthesis, and optimization of these hybrid catalysts as well as material about their application. The contributors—noted experts in the field—present information on the preparation, characterization, and optimization of artificial metalloenzymes in a timely and authoritative manner. The authors present a thorough examination of this interesting new platform for catalysis that combines the excellent selective recognition/binding properties of enzymes with transition metal catalysts. The text includes information on the various applications of metal-enzyme hybrid catalysts for novel reactions, offers insights into the latest advances in the field, and contains an informative perspective on the future: Explores the development of artificial metalloenzymes, the modern and strongly evolving research field on the verge of industrial application Contains a comprehensive reference to the research area of metal-enzyme hybrid catalysis that has experienced tremendous growth in recent years Includes contributions from leading researchers in the field Shows how this new catalysis combines the selective recognition/binding properties of enzymes with transition metal catalysts Written for catalytic chemists, bioinorganic chemists, biochemists, and organic chemists, Artificial Metalloenzymes and MetalloDNAzymes in Catalysis offers a unique reference to the fundamentals, concepts, applications, and the most recent developments for more efficient and sustainable synthesis.

Catalytic Asymmetric Synthesis

Catalytic Asymmetric Synthesis
Author: Takahiko Akiyama
Publisher: John Wiley & Sons
Total Pages: 798
Release: 2022-05-27
Genre: Science
ISBN: 1119736412

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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.

Synthetic Applications

Synthetic Applications
Author: Rajender S. Varma
Publisher: Walter de Gruyter GmbH & Co KG
Total Pages: 578
Release: 2022-05-09
Genre: Science
ISBN: 3110730472

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Magnetic nanocatalysts are becoming an important tool for greener catalytic processes in chemical transformations in view of the ease of their removal from a reaction medium. This book explores assorted magnetic nanocatalysts, their deployment in synthesis, chemical transformation and their recovery and reuse. Various thematic topics embodied include magnetic nanocatalysts for S-S bond formation, N-heterocycle formation, C-heteroatom bond formation, silica-supported catalysts, multicomponent reactions, including their recyclability; another available volume emphasizes the utility of magnetic nanocatalysts in industrial appliances.

Homogeneous Gold Catalysis

Homogeneous Gold Catalysis
Author: LeGrande M. Slaughter
Publisher: Springer
Total Pages: 292
Release: 2015-03-30
Genre: Science
ISBN: 3319137220

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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.

Gold Catalysis: An Homogeneous Approach

Gold Catalysis: An Homogeneous Approach
Author: Veronique Michelet
Publisher: World Scientific
Total Pages: 564
Release: 2014-06-20
Genre: Science
ISBN: 1783265558

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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.

Selective Glycosylations

Selective Glycosylations
Author: Clay S. Bennett
Publisher: John Wiley & Sons
Total Pages: 398
Release: 2017-01-25
Genre: Science
ISBN: 3527696229

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A comprehensive summary of novel approaches to the stereoselective construction of glycosidic linkages, covering modern glycosylation methods and their use and application in natural product synthesis and drug discovery. Clearly divided into five sections, the first describes recent advances in classical methodologies in carbohydrate chemistry, while the second goes on to deal with newer chemistries developed to control selectivity in glycosylation reactions. Section three is devoted to selective glycosylation reactions that rely on the use of catalytic promoters. Section four describes modern approaches for controlling regioselectivity in carbohydrate synthesis. The final section focuses on new developments in the construction of "unusual" sugars and is rounded off by a presentation of modern procedures for the construction of glycosylated natural products. By providing the latest advances in glycosylation as well as information on mechanistic aspects of the reaction, this is an invaluable reference for both specialists and beginners in this booming interdisciplinary field that includes carbohydrate chemistry, organic synthesis, catalysis, and biochemistry.

March's Advanced Organic Chemistry

March's Advanced Organic Chemistry
Author: Michael B. Smith
Publisher: John Wiley & Sons
Total Pages: 2379
Release: 2007-01-29
Genre: Science
ISBN: 0470084944

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The Sixth Edition of a classic in organic chemistry continues its tradition of excellence Now in its sixth edition, March's Advanced Organic Chemistry remains the gold standard in organic chemistry. Throughout its six editions, students and chemists from around the world have relied on it as an essential resource for planning and executing synthetic reactions. The Sixth Edition brings the text completely current with the most recent organic reactions. In addition, the references have been updated to enable readers to find the latest primary and review literature with ease. New features include: More than 25,000 references to the literature to facilitate further research Revised mechanisms, where required, that explain concepts in clear modern terms Revisions and updates to each chapter to bring them all fully up to date with the latest reactions and discoveries A revised Appendix B to facilitate correlating chapter sections with synthetic transformations