Catalytic Generation and C-C Bond Forming Reactions of Dicoordinated Carbocations
Catalytic Generation and C-C Bond Forming Reactions of Dicoordinated Carbocations

Author: Stanislav Popov

Publisher:

Published: 2021

Total Pages: 511

ISBN-13:

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This dissertation describes the development of Lewis acid-based methodology togenerate dicoordinated carbocations catalytically. These reactive intermediates were once sparingly accessible synthetically and were mostly the focus of theoretical studies. This dissertation highlights new, mild conditions that can generate these species in a kinetically persistent fashion through the use of weakly coordinating anions in non-polar media. These conditions also enable new carbon-carbon bond forming reactions of these intermediates to take place; either through Friedel-Crafts or C-H insertion. Additionally mechanistic nuances and the key advantages and disadvantages of each developed system will be highlighted. Overall, this work features the development of this chemistry from a fundamental study to a more broadly applicable reaction. Chapter One is a brief overview of the current state of research on aryl and vinyl cations. This chapter serves as a prelude to the remaining chapters and will be referenced throughout this dissertation. Strategies to generate these reactive species, specifically ones that inspired our own research in this area are presented. Furthermore, some reactivity of these cations is also highlighted, again focusing on mechanistically similar reactions to our own. Chapter Two describes our efforts in the development of a silylium-carborane catalyzed reaction to generate aryl and vinyl cations catalytically from aryl fluorides and vinyl triflates respectively. These species were then able to be engaged in intermolecular reactions with inert C-H bonds of both alkanes and arenes resulting in a mild C-H functionalization reaction. Chapter Three discusses our investigations of lithium-based Lewis acids to generate reaction vinyl cations under highly basic conditions and their ensuing reactivity. Notably, this work also overcomes some of the challenges presented in chapter Two with regards to the functional group compatibility of these systems. This work represents an important advancement of our chemistry towards a more robust, practical reaction. Chapter Four highlights an ongoing effort in our research group to utilize different vinyl sulfonate precursors in order to access a broader class of vinyl cation intermediates. With these precursors in hand, we utilize similar conditions to Chapter Three to develop some new vinyl cation reactivity. These reactions involve trapping of vinyl cations with allylsilanes, silyl ketene acetals, and methyl ethers. Chapter Five discusses our ongoing effort to develop a "field guide" for the practicing organic chemist in order to disseminate some of our groups in-house knowledge in developing these cation methodologies over the past few years. Here, mechanistic nuances, substrate design, and choice of catalytic system are discussed.

Main Group-Catalyzed Carbon to Carbon Bond-Forming Reactions of Dicoordinate Carbocations
Main Group-Catalyzed Carbon to Carbon Bond-Forming Reactions of Dicoordinate Carbocations

Author: Alex Levon Bagdasarian

Publisher:

Published: 2019

Total Pages: 334

ISBN-13:

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This dissertation focuses on the development of catalytic Carbon to Carbon (C-C) bond forming reactions of dicoordinate carbocations. The unique reactivity described herein focuses on the use of ionizable groups and appropriate counter anions to facilitate productive reactions of high-energy cationic intermediates. The first chapter discusses the exploration of phenyl carbocations, generated from aryl fluorides under silylium-weakly coordinating anion (WCA) catalysis, in the context of hydrocarbon functionalization. Chapter two describes the discovery of C-H insertion and reductive Friedel-Crafts reactions of vinyl carbocations generated from vinyl triflates and silylium-WCA salts. Chapter three describes a novel approach to generating vinyl cations using Lithium Lewis acids. Interestingly, these vinyl carbocations are formed under basic conditions, with lithium hexamethyldisilazide (LiHMDS) as the Lewis acid precursor. Chapter four describes two new catalytic manifolds using urea-based organocatalysts. In one instance, the urea catalyst directly ionizes the vinyl triflate through a hydrogen-bonding interaction to promote intra molecular C-H insertion reactions. In another case, urea organocatalysts combined with LiHMDS, result in novel lithium-urea catalyst that promote Friedel-Crafts reactions of vinyl triflates. In summary, these studies have resulted in the development of new catalytic methods using main-group catalysis for the formation of C-C bonds.

Enantioselective C-C Bond Forming Reactions
Enantioselective C-C Bond Forming Reactions

Author:

Publisher: Elsevier

Published: 2023-12-01

Total Pages: 338

ISBN-13: 044323700X

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Enantioselective C-C Bond Forming Reactions: From Metal Complex-, Organo-, and Bio-catalyzed Perspectives, Volume 73 in the Advances in Catalysis series, highlights new advances in the field, with this new volume presenting interesting chapters on topics such as An introduction to Chirality, Metal-catalyzed stereoselective C-C-bond forming reactions, Enantioselective C-C bond forming reactions promoted by organocatalysts based on unnatural amino acid derivatives, Enantioselective C-C bond formation in complex multicatalytic system, Gold-based multicatalytic systems for enantioselective C-C Bond forming reactions, Novel enzymatic tools for C-C bond formation through the development of new-to-nature biocatalysis, and more. Provides the authority and expertise of leading contributors from an international board of authors Presents the latest release in Advances in Catalysis serials Updated release includes the latest information in the field

Discovery and Mechanistic Insights of Main-Group Catalyzed C-H Functionalization Reactions of Dicoordinate Carbocations
Discovery and Mechanistic Insights of Main-Group Catalyzed C-H Functionalization Reactions of Dicoordinate Carbocations

Author: Brian Shao

Publisher:

Published: 2019

Total Pages: 240

ISBN-13:

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This dissertation focuses on the discovery and developments of novel carbon-carbon (C-C) bond forming reactions through dicoordinate carbocation intermediates. Chapter one provides a brief introduction into the known reactivity of relevant aryl and vinyl carbocations. In particular, C-C bond forming transformations will be the main focus of this discussion. Our experimental work begins with the account of serendipitous discovery of intermolecular C-H insertion reactions of an aryl cation intermediate. We detail the reactivity-driven nature of our initial hypothesis and its development into a novel hydrocarbon arylation methodology. It was demonstrated that ortho-silylated aryl fluorides can be used as precursors for generating aryl cations capable of C-H insertion. The insertion chemistry exhibits inherent terminal selectivity in linear alkanes and is capable of activating one of the most challenges C-H bonds in methane. Subsequently, we followed the reactivity of our aryl cations to other dicoordinate carbocations as in vinyl cations. Utilizing a similar strategy hinged upon the use of silylium-weakly coordinating anion catalysis, vinyl cations were found to also undergo intermolecular insertion into sp3 C-H bonds. Here, we establish a reductive coupling process between vinyl triflates and various hydrocarbons. Extensive deuterium labeling studies also helped to uncover key features of the dicoordinate carbocation insertion mechanism. A detailed account of our hypotheses in establishing our mechanistic probe experiments is reported. In efforts to bring our new methodology to a more broadly applicable chemical space, we were determined to further develop our system for heteroatom compatibility. Our progress has culminated in a new mode of generation for vinyl cations under highly basic conditions, and results in the C-H insertion reactions in the presence of a wide variety of heteroatom-containing substrates. In these studies, 3-substitued cyclooctenyl vinyl triflates was a substrate class used to highlight the increased functional group tolerance of our new method. Utilization of lithium-weakly coordinating anions has allowed entry for our dicoordinate carbocation insertion chemistry into applications such as fine chemical syntheses.

Carbon-Carbon ?-Bond Formation
Carbon-Carbon ?-Bond Formation

Author: G. Pattenden

Publisher: Elsevier

Published: 1992-09-08

Total Pages: 1209

ISBN-13: 008091246X

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Volume 3 covers carbon-to-carbon single bond forming reactions involving sp3, sp2 and sp carbon centers, but only those which do not involve additions to C-X &pgr;-bonds. The volume first compares and contrasts the alkylation reactions of all types of sp3 carbon nucleophiles and also covers vinyl and alkynyl carbanions. Following on from Volume 2, a separate section covers Friedel-Crafts alkylation reactions, which is complemented by discussions of polyene cyclizations and electrophilic transannular cyclizations in synthesis. Coupling reactions leading to &agr;-bond formation, and involving all types of combinations ofsp3, sp2 and sp carbon centers are next covered, including those reactions based on pinacol, acyloin and phenol oxidative coupling reactions, and also the Kolbe reaction. Rearrangement reactions, leading to carbon-to-carbon &agr;-bond formation, are often used in a clever manner in synthesis. The volume includes all those rearrangement reactions based on intermediate carbonium ions and carbanions, and also includes the benzil-benzilic acid and the Wolff rearrangements. The volume closes with coverage of carbonylation reactions, and the use of carbene insertion reactions into the C-H bond in synthesis.

New Carbon–Carbon Coupling Reactions Based on Decarboxylation and Iron-Catalyzed C–H Activation
New Carbon–Carbon Coupling Reactions Based on Decarboxylation and Iron-Catalyzed C–H Activation

Author: Rui Shang

Publisher: Springer

Published: 2016-12-09

Total Pages: 225

ISBN-13: 9811031932

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This thesis presents the latest developments in new catalytic C–C bond formation methods using easily accessible carboxylate salts through catalytic decarboxylation with good atom economy, and employing the sustainable element iron as the catalyst to directly activate C–H bonds with high step efficiency. In this regard, it explores a mechanistic understanding of the newly discovered decarboxylative couplings and the catalytic reactivity of the iron catalyst with the help of density functional theory calculation. The thesis is divided into two parts, the first of which focuses on the development of a series of previously unexplored, inexpensive carboxylate salts as useful building blocks for the formation of various C–C bonds to access valuable chemicals. In turn, the second part is devoted to several new C–C bond formation methodologies using the most ubiquitous transition metal, iron, as a catalyst, and using the ubiquitous C–H bond as the coupling partner.

Dicoordinated Carbocations
Dicoordinated Carbocations

Author: Zvi Rappoport

Publisher: Wiley-Blackwell

Published: 1997-12-29

Total Pages: 488

ISBN-13:

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The first title in this area in many years, this title brings together all the areas of interest in organic reactions involving carbocations in one handy volume. It covers new areas such as nuclear decay generation, synthetic applications and NMR observations. Also included is extensive and detailed coverage of theoretical and gas phase data.