Organic Reactions, Volume 102 E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: Organic Reactions
• Sprache: Englisch

Seitenzahl: 392

Veröffentlichungsjahr: 2020

Beschreibung

The 102nd volume in this series for organic chemists in academia and industry presents critical discussions of widely used organic reactions or particular phases of a reaction. The material is treated from a preparative viewpoint, with emphasis on limitations, interfering influences, effects of structure and the selection of experimental techniques. The work includes tables that contain all possible examples of the reaction under consideration. Detailed procedures illustrate the significant modifications of each method.

Leseprobe

Table of Contents

Cover

Introduction to the Series Roger Adams, 1942

Introduction to the Series Scott E. Denmark, 2008

Preface to Volume 102

Chapter 1: The Brook Rearrangement

Introduction

Mechanism and Stereochemistry

Scope and Limitations

Applications to Synthesis

Comparison With Other Methods

Experimental Conditions

Experimental Procedures

Tabular Survey

References

Chapter 2: Alkyne Metathesis

Introduction

Mechanism and Stereochemistry

Scope and Limitations

Applications to Synthesis

Comparison With Other Methods

Experimental Conditions

Experimental Procedures

Tabular Survey

References

Supplemental References for Table 1

Supplemental References for Table 3

Supplemental References for Table 4

Supplemental References for Table 5

Cumulative Chapter Titles by Volume

Volume 1 (1942)

Volume 2 (1944)

Volume 3 (1946)

Volume 4 (1948)

Volume 5 (1949)

Volume 6 (1951)

Volume 7 (1953)

Volume 8 (1954)

Volume 9 (1957)

Volume 10 (1959)

Volume 11 (1960)

Volume 12 (1962)

Volume 13 (1963)

Volume 14 (1965)

Volume 15 (1967)

Volume 16 (1968)

Volume 17 (1969)

Volume 18 (1970)

Volume 19 (1972)

Volume 20 (1973)

Volume 21 (1974)

Volume 22 (1975)

Volume 23 (1976)

Volume 24 (1976)

Volume 25 (1977)

Volume 26 (1979)

Volume 27 (1982)

Volume 28 (1982)

Volume 29 (1983)

Volume 30 (1984)

Volume 31 (1984)

Volume 32 (1984)

Volume 33 (1985)

Volume 34 (1985)

Volume 35 (1988)

Volume 36 (1988)

Volume 37 (1989)

Volume 38 (1990)

Volume 39 (1990)

Volume 40 (1991)

Volume 41 (1992)

Volume 42 (1992)

Volume 43 (1993)

Volume 44 (1993)

Volume 45 (1994)

Volume 46 (1994)

Volume 47 (1995)

Volume 48 (1995)

Volume 49 (1997)

Volume 50 (1997)

Volume 51 (1997)

Volume 52 (1998)

Volume 53 (1998)

Volume 54 (1999)

Volume 55 (1999)

Volume 56 (2000)

Volume 57 (2001)

Volume 58 (2001)

Volume 59 (2001)

Volume 60 (2002)

Volume 61 (2002)

Volume 62 (2003)

Volume 63 (2004)

Volume 64 (2004)

Volume 65 (2005)

Volume 66 (2005)

Volume 67 (2006)

Volume 68 (2007)

Volume 69 (2007)

Volume 70 (2008)

Volume 71 (2008)

Volume 72 (2008)

Volume 73 (2008)

Volume 74 (2009)

Volume 75 (2011)

Volume 76 (2012)

Volume 77 (2012)

Volume 78 (2012)

Volume 79 (2013)

Volume 80 (2013)

Volume 81 (2013)

Volume 82 (2013)

Volume 83 (2014)

Volume 84 (2014)

Volume 85 (2014)

Volume 86 (2015)

Volume 87 (2015)

Volume 88 (2015)

Volume 89 (2015)

Volume 90 (2016)

Volume 91 (2016)

Volume 92 (2016–2017)

Volume 93 (2017)

Volume 94 (2017)

Volume 95 (2018)

Volume 96 (2018)

Volume 97 (2018)

Volume 98 (2019)

Volume 99 (2019)

Volume 100 (2020)

Volume 101 (2020)

Author Index, Volumes 1–102

Chapter and Topic Index, Volumes 1–102

End User License Agreement

List of Tables

Chapter 1

Chart 1. Catalysts Used in the Tables

Chart 2. Ligands Used in the Tables

Table 1A. Brook Rearrangement of Acylsilanes with Aldehydes as Electrophiles

Table 1B. Brook Rearrangement of Acylsilanes with Ketones as Electrophiles

Table 1C. Brook Rearrangement of Acylsilanes with Carboxylic Acid Derivatives as...

Table 1D. Brook Rearrangement of Acylsilanes with Imines as Electrophiles

Table 1E. Brook Rearrangement of Acylsilanes with Electrophilic Alkenes as Elect...

Table 1F. Brook Rearrangement of Acylsilanes with Organohalides and Their Analog...

Table 1G. Brook Rearrangement of Acylsilanes with Heteroatom Electrophiles

Table 1H. Brook Rearrangement of Acylsilanes with Protons as Electrophiles

Table 1I. Brook Rearrangement of Acylsilanes Followed by Elimination

Table 1J. Brook Rearrangement of Acylsilanes Followed by Other Miscellaneous Tra...

Table 2A. Brook Rearrangement of Keto Silanes with Carbonyl Acceptors as Elec...

Table 2B. Brook Rearrangement of Keto Silanes with Epoxides as Electrophiles

Table 2C. Brook Rearrangement of Keto Silanes with Organohalides and Their Analo...

Table 2D. Brook Rearrangement of Keto Silanes with Heteroatom Electrophiles

Table 2E. Brook Rearrangement of Keto Silanes with Protons as Electrophiles

Table 2F. Brook Rearrangement of Keto Silanes Followed by Miscellaneous Transfor...

Table 3A. Brook Rearrangement of Epoxysilanes with Carbonyl Acceptors as Elec...

Table 3B. Brook Rearrangement of Epoxysilanes with Electrophilic Alkenes as Elec...

Table 3C. Brook Rearrangement of Epoxysilanes with Epoxides or Aziridines as Ele...

Table 3D. Brook Rearrangement of Epoxysilanes with Organohalides and Their Analo...

Table 3E. Brook Rearrangement of Epoxysilanes with Protons as Electrophiles

Table 3F. Brook Rearrangement of Epoxysilanes Followed by Miscellaneous Transfor...

Table 4A. Brook Rearrangement of Hydroxysilanes with Carbonyl Acceptors as El...

Table 4B. Brook Rearrangement of Hydroxysilanes with Electrophilic Alkenes as El...

Table 4C. Brook Rearrangement of Hydroxysilanes with Epoxides as Electrophiles

Table 4D. Brook Rearrangement of Hydroxysilanes with Organohalides and Their Ana...

Table 4E. Brook Rearrangement of Hydroxysilanes with Heteroatom Electrophiles

Table 4F. Brook Rearrangement of Hydroxysilanes with Protons as Electrophiles

Table 4G. Brook Rearrangement of Hydroxylsilanes Followed by Miscellaneous Trans...

Table 5A. Brook Rearrangement of Silyl Carbanions with Carbonyl Acceptors as ...

Table 5B. Brook Rearrangement of Silyl Carbanions with Electrophilic Alkenes as ...

Table 5C. Brook Rearrangement of Silyl Carbanions with Epoxides as Electrophiles

Table 5D. Brook Rearrangement of Silyl Carbanions with Organohalides and Their A...

Table 5E. Brook Rearrangement of Silyl Carbanions with Heteroatom Electrophiles

Table 5F. Brook Rearrangement of Silyl Carbanions with Protons as Electrophiles

Table 5G. Brook Rearrangement of Silyl Carbanions Followed by Elimination

Table 5H. Brook Rearrangement of Silyl Carbanions Followed by Other Miscellaneou...

Table 6A. Brook Rearrangement of Silylmetallic Compounds with Carbonyl Accept...

Table 6B. Brook Rearrangement of Silylmetallic Compounds with Organohalides and ...

Table 6C. Brook Rearrangement of Silylmetallic Compounds with Protons as Electro...

Table 6D. Brook Rearrangement of Silylmetallic Compounds Followed by Elimination

Table 6E. Brook Rearrangement of Silylmetallic Compounds Followed by Other Misce...

Chapter 2

Table 1. Alkyne Homo-Metathesis

Table 2. Alkyne Cross-Metathesis

Table 3. Ring-Closing Alkyne Metathesis

Table 4. Alkyne Metathesis Cyclooligomerization

Table 5. Alkyne Metathesis Polymerization

Table 6. Depolymerization–Cyclooligomerization

List of Illustrations

Chapter 1

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Chapter 2

Scheme 1

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Scheme 15

Figure 1 Well‐defined single‐component catalysts for alkyne metathesis.

Figure 2. Well‐defined, tungsten‐based catalysts for alkyne metathesis.

Scheme 16

Scheme 17

Figure 3. Resonance forms of the imidazolin‐2‐iminato ligand.

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Figure 4 Molybdenum nitrido complexes for alkyne metathesis.

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Figure 5 Single‐component Schrock‐type molybdenum alkylidyne complexes.

Scheme 29

Figure 6 Well‐defined heterogeneous catalysts grafted onto silica gel surfac...

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Figure 7 Macrocycles synthesized by RCAM/

trans

‐selective semi‐reduction prot...

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Guide

Cover

Table of Contents

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Advisory Board

John E. Baldwin

Steven V. Ley

Peter Beak

James A. Marshall

Dale L. Boger

Michael J. Martinelli

André B. Charette

Stuart W. Mc Combie

Engelbert Ciganek

Scott J. Miller

Dennis Curran

John Montgomery

Samuel Danishefsky

Larry E. Overman

Huw M. L. Davies

T. V. RajanBabu

Scott E. Denmark

Hans J. Reich

John Fried

James H. Rigby

Jacquelyn Gervay‐Hague

William R. Roush

Heinz W. Gschwend

Tomislav Rovis

Stephen Hanessian

Scott D. Rychnovsky

Louis Hegedus

Martin Semmelhack

Paul J. Hergenrother

Charles Sih

Jeffrey S. Johnson

Amos B. Smith, III

Robert C. Kelly

Barry M. Trost

Laura Kiessling

James D. White

Marisa C. Kozlowski

Peter Wipf

Former Members of the Board Now Deceased

Roger Adams

Herbert O. House

Homer Adkins

John R. Johnson

Werner E. Bachmann

Robert M. Joyce

A. H. Blatt

Andrew S. Kende

Robert Bittman

Willy Leimgruber

Virgil Boekelheide

Frank C. Mc Grew

George A. Boswell, Jr.

Blaine C. Mc Kusick

Theodore L. Cairns

Jerrold Meinwald

Arthur C. Cope

Carl Niemann

Donald J. Cram

Leo A. Paquette

David Y. Curtin

Gary H. Posner

William G. Dauben

Harold R. Snyder

Richard F. Heck

Milán Uskokovic

Louis F. Fieser

Boris Weinstein

Ralph F. Hirschmann

Organic Reactions

Volume 102

Editorial Board

P. Andrew Evans, Editor-in-Chief

Steven M. Weinreb, Executive Editor

Jeffrey Aubé

Jennifer A. Love

David B. Berkowitz

Gary A. Molander

Paul R. Blakemore

Albert Padwa

Jin K. Cha

Jennifer M. Schomaker

Dennis G. Hall

Kevin H. Shaughnessy

Donna M. Huryn

Christopher D. Vanderwal

Jeffery B. Press, Secretary

Press Consulting Partners, Brewster, New York

Danielle Soenen, Editorial Coordinator

Dena Lindsay, Secretary and Processing Editor

Landy K. Blasdel, Processing Editor

Debra Dolliver, Processing Editor

Engelbert Ciganek, Editorial Advisor

ASSOCIATE EDITORS

Lu Gao

Daesung Lee

Zhenlei Song

Ivan Volchkov

Ya Wu

Wenyu Yang

Sang Young Yun

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Library of Congress Cataloging‐in‐Publication Data: ISBN: 978‐1‐119‐65122‐2

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

Introduction to the Series Roger Adams, 1942

In the course of nearly every program of research in organic chemistry, the investigator finds it necessary to use several of the better‐known synthetic reactions. To discover the optimum conditions for the application of even the most familiar one to a compound not previously subjected to the reaction often requires an extensive search of the literature; even then a series of experiments may be necessary. When the results of the investigation are published, the synthesis, which may have required months of work, is usually described without comment. The background of knowledge and experience gained in the literature search and experimentation is thus lost to those who subsequently have occasion to apply the general method. The student of preparative organic chemistry faces similar difficulties. The textbooks and laboratory manuals furnish numerous examples of the application of various syntheses, but only rarely do they convey an accurate conception of the scope and usefulness of the processes.

For many years American organic chemists have discussed these problems. The plan of compiling critical discussions of the more important reactions thus was evolved. The volumes of Organic Reactions are collections of chapters each devoted to a single reaction, or a definite phase of a reaction, of wide applicability. The authors have had experience with the processes surveyed. The subjects are presented from the preparative viewpoint, and particular attention is given to limitations, interfering influences, effects of structure, and the selection of experimental techniques. Each chapter includes several detailed procedures illustrating the significant modifications of the method. Most of these procedures have been found satisfactory by the author or one of the editors, but unlike those in Organic Syntheses, they have not been subjected to careful testing in two or more laboratories. Each chapter contains tables that include all the examples of the reaction under consideration that the author has been able to find. It is inevitable, however, that in the search of the literature some examples will be missed, especially when the reaction is used as one step in an extended synthesis. Nevertheless, the investigator will be able to use the tables and their accompanying bibliographies in place of most or all of the literature search so often required. Because of the systematic arrangement of the material in the chapters and the entries in the tables, users of the books will be able to find information desired by reference to the table of contents of the appropriate chapter. In the interest of economy, the entries in the indices have been kept to a minimum, and, in particular, the compounds listed in the tables are not repeated in the indices.

The success of this publication, which will appear periodically, depends upon the cooperation of organic chemists and their willingness to devote time and effort to the preparation of the chapters. They have manifested their interest already by the almost unanimous acceptance of invitations to contribute to the work. The editors will welcome their continued interest and their suggestions for improvements in Organic Reactions.

Introduction to the Series Scott E. Denmark, 2008

In the intervening years since “The Chief” wrote this introduction to the second of his publishing creations, much in the world of chemistry has changed. In particular, the last decade has witnessed a revolution in the generation, dissemination, and availability of the chemical literature with the advent of electronic publication and abstracting services. Although the exponential growth in the chemical literature was one of the motivations for the creation of Organic Reactions, Adams could never have anticipated the impact of electronic access to the literature. Yet, as often happens with visionary advances, the value of this critical resource is now even greater than at its inception.

From 1942 to the 1980's the challenge that Organic Reactions successfully addressed was the difficulty in compiling an authoritative summary of a preparatively useful organic reaction from the primary literature. Practitioners interested in executing such a reaction (or simply learning about the features, advantages, and limitations of this process) would have a valuable resource to guide their experimentation. As abstracting services, in particular Chemical Abstracts and later Beilstein, entered the electronic age, the challenge for the practitioner was no longer to locate all of the literature on the subject. However, Organic Reactions chapters are much more than a surfeit of primary references; they constitute a distillation of this avalanche of information into the knowledge needed to correctly implement a reaction. It is in this capacity, namely to provide focused, scholarly, and comprehensive overviews of a given transformation, that Organic Reactions takes on even greater significance for the practice of chemical experimentation in the 21st century.

Adams' description of the content of the intended chapters is still remarkably relevant today. The development of new chemical reactions over the past decades has greatly accelerated and has embraced more sophisticated reagents derived from elements representing all reaches of the Periodic Table. Accordingly, the successful implementation of these transformations requires more stringent adherence to important experimental details and conditions. The suitability of a given reaction for an unknown application is best judged from the informed vantage point provided by precedent and guidelines offered by a knowledgeable author.

As Adams clearly understood, the ultimate success of the enterprise depends on the willingness of organic chemists to devote their time and efforts to the preparation of chapters. The fact that, at the dawn of the 21st century, the series continues to thrive is fitting testimony to those chemists whose contributions serve as the foundation of this edifice. Chemists who are considering the preparation of a manuscript for submission to Organic Reactions are urged to contact the Editor‐in‐Chief.

Preface to Volume 102

The man who moves a mountain begins by carrying away small stones.

Confucius, The Analects

The development of a new chemical reaction often begins with a preliminary discovery that, over time, blossoms into a vast body of chemical knowledge that is compiled by the synthetic community. Although there is undoubtedly an element of serendipity in the initial discovery, the hard work that translates the so‐called “small stones into a mountain” occurs over time through innovative contributions that facilitate the development of the transformation into a sophisticated and broad process. Hence, while the importance of a reaction is often underestimated at the outset, the delineation of detailed insights into scope and mechanism along with successful application to total synthesis drives the development of the process into an essential tool for all types of synthetic applications. The two chapters in this volume of Organic Reactions illustrate this notion and serve as examples of how a simple discovery can evolve into a sophisticated and powerful synthetic method, which, in one case, is recognized as a named reaction. Ironically, these two seemingly dissimilar reactions both involve processes where atoms “change places” in a predictable manner to permit the formation of important new C‐C bonds. Moreover, the reactions have been utilized to control both sp2 and sp3 stereochemistry, which permits new strategic thinking that would be challenging using conventional reactions.

The first chapter by Lu Gao, Wenyu Yang, Ya Wu, and Zhenlei Song is an outstanding treatise on the venerable Brook rearrangement. The research on this rearrangement dates back to the early 1950s when Adrian Brook discovered the rearrangement by accident while completing postdoctoral studies with Henry Gilman at Iowa State University. Thus, in the course of the attempted addition of triphenylsilylpotassium to benzophenone, he observed “an unexpected product” from the migration of the silyl group after nucleophilic addition into the carbonyl. During his independent career, Brook developed a detailed mechanistic understanding of this process, in which he demonstrated that the product is derived from the standard addition to the carbonyl group, followed by an intramolecular anionic carbon‐to‐oxygen silyl group migration to furnish a carbanion. This chapter now provides a complete summary of the mechanistic aspects of the reaction, which includes both anionic and neutral variants, in which the latter is further subdivided into radical and concerted processes. The fascination with this rearrangement has provided many significant contributions that have resulted in an arsenal of intramolecular carbon‐to‐oxygen silyl group migrations. The authors have nicely organized the Scope and Limitations section according to six types of organosilanes employed to generate the reactive silyl oxyanion intermediates, namely, acylsilanes, ketosilanes, epoxysilanes, hydroxysilanes, silyl carbanions, and silylmetallic species. The silane sections are then further subdivided by the terminating electrophile (e.g., carbonyl acceptors, electrophilic alkenes, epoxides, organohalides, heteroatom electrophiles, proton, etc.). The comprehensive Tabular Survey is primarily organized in a similar manner, which makes the identification of the optimal reaction and the associated conditions relatively simple for the reader. Overall, this is an outstanding chapter on an important named reaction, which I trust will be an essential primary reference for the synthetic community.

The second chapter by Daesung Lee, Ivan Volchkov, and Sang Young Yun delineates the historical development of alkyne metathesis, which has not been as extensively studied as the alkene variant. This process is very challenging and the chapter focusses on the merits of specific catalysts and how they perform in various scenarios. For instance, there have been significant developments in new catalysts since Bailey described the first metal‐catalyzed alkyne metathesis using tungsten trioxide and silica. The chapter compares and contrasts the utility of the in situ‐generated molybdenum‐based catalytic systems reported by Mortreux, the well‐defined molybdenum‐ and tungsten‐based catalysts with alkoxide and phenoxide ligands, and Fürstner's silanolate‐ligated molybdenum alkylidyne complexes. The new catalyst systems have significantly improved air and moisture stability, high catalytic activity, in addition to providing outstanding functional‐group compatibility, which has significantly broadened the scope and utility of alkyne metathesis. The Scope and Limitations section is organized into four main categories, namely alkyne cross‐metathesis (ACM), ring‐closing alkyne metathesis (RCAM), ring‐opening alkyne metathesis polymerization (ROAMP), and acyclic diyne metathesis polymerization (ADIMET). Notably, the chapter provides the reader with a perspective of the knowledge gaps in the context of the current limitations with specific classes of reactions, which thereby offers important research opportunities. Furthermore, the sections on the Applications to Synthesis and the Comparison with Other Methods outline the synthetic utility and the importance of this process over the most prominent alternatives. For instance, alkyne metathesis offers unique chemoselectivity and the ability to selectively prepare either the (E)‐ or (Z)‐olefin from the alkyne, which significantly contrasts conventional alkene metathesis reactions. The Tabular Survey mirrors the Scope and Limitations section, which is arranged based on the type of metathesis, namely homometathesis (albeit terminal alkyne metathesis is included in this section), cross‐metathesis, and ring‐closing metathesis. Overall, this chapter provides the reader with an outstanding opportunity to familiarize themselves with the current state‐of‐the‐art and critical knowledge gaps in this importantarea.

I would be remiss if I did not acknowledge the entire Organic Reactions Editorial Board for their collective efforts in steering the chapters through the various stages of the editorial process. I would like to particularly thank Jeffrey S. Johnson (Chapter 1) for his early efforts before I took it over and Jin K. Cha (Chapter 2), who served as the Responsible Editors and marshaled the chapters through the various phases of development. I am also deeply indebted to Dr. Danielle Soenen for her continuous efforts as the Editorial Coordinator; her knowledge of Organic Reactions is a critical component to maintaining consistency in the series. Dr. Dena Lindsay (Secretary to the Editorial Board) is thanked for coordinating the contributions of the authors, editors, and publishers. In addition, the Organic Reactions enterprise could not maintain the quality of production without the efforts of Steven Weinreb (Executive Editor), Dr. Linda S. Press (Editorial Consultant), Dr. Engelbert Ciganek (Editorial Advisor), Dr. Landy Blasdel (Processing Editor), and Dr. Debra Dolliver (Processing Editor). I would also like to acknowledge Dr. Jeffery Press (Secretary‐Treasurer) for his constant effort to keep everyone on task and his attention to making sure that we are fiscally solvent!

I am indebted to all the individuals that are dedicated to ensuring the quality of Organic Reactions. The unique format of the chapters, in conjunction with the collated tables of examples, make this series of reviews both unique and exceptionally useful to the practicing synthetic organic chemist.

P. Andrew Evans

Kingston

Ontario, Canada

Chapter 1The Brook Rearrangement

Lu Gao, Wenyu Yang, and Zhenlei Song,

Sichuan Engineering Laboratory for Plant‐Sourced Drug and Research Center for Drug Industrial Technology, Key Laboratory of Drug‐Targeting and Drug Delivery System of the Education Ministry, West China School of Pharmacy, Sichuan University, Chengdu, 610064, P. R. China

Ya Wu

School of Biological and Chemical Engineering, Chongqing University of Education, Chongqing, 400067, P. R. China

Edited by P. Andrew Evans

Contents

Introduction

Mechanism and Stereochemistry

The Anionic Brook Rearrangement

Mechanism

Stereochemistry

The Neutral Brook Rearrangement

Radical‐Type Silyl Migrations

Concerted‐Type Silyl Migration

Scope and Limitations

Brook Rearrangements of Acylsilanes

Carbon Electrophiles

Carbonyl Acceptors

Aldehydes and Ketones

Carboxylic Acid Derivatives

Imines

Electrophilic Alkenes

α,β‐Unsaturated Carbonyl Compounds

Nitroalkenes

Organohalides

Heteroatom Electrophiles

A Proton as the Electrophile

Miscellaneous Transformations Following the Brook Rearrangement

Eliminations

Cyclizations

Sigmatropic Rearrangements

Siloxycarbene‐Mediated Reactions

Release of Carbon Monoxide

Brook Rearrangements of Keto Silanes

Carbon Electrophiles

Carbonyl Acceptors

Aldehydes and Ketones

Carboxylic Acid Derivatives

Epoxides

Organohalides and Their Analogs

Heteroatom Electrophiles

A Proton as the Electrophile

Miscellaneous Transformations Following the Brook Rearrangement

Eliminations

Brook Rearrangements of Epoxysilanes

Carbon Electrophiles

Carbonyl Acceptors

Electrophilic Alkenes

Epoxides and Aziridines

Organohalides

A Proton as the Electrophile

Miscellaneous Transformations Following the Brook Rearrangement

Eliminations

Retro‐Brook Rearrangements

[2,3]‐Wittig Rearrangements

Brook Rearrangements of Hydroxysilanes

Carbon Electrophiles

Carbonyl Acceptors

Aldehydes and Ketones

Carboxylic Acid Derivatives

Electrophilic Alkenes

Organohalides and Their Analogs

Heteroatom Electrophiles

A Proton as the Electrophile

Miscellaneous Transformations Following the Brook Rearrangement

Eliminations

Brook Rearrangements of Silyl Carbanions

Carbon Electrophiles

Carbonyl Acceptors

Electrophilic Alkenes

Epoxides

Organohalides and Their Analogs

Miscellaneous Transformations Following the Brook Rearrangement

Eliminations

Protonations/1,2‐C–H or C–C Bond Migrations

[3 + 2]‐Dipolar Cycloadditions

Retro‐Brook Rearrangements

Brook Rearrangements of Silylmetallic Compounds

Carbon Electrophiles

Carbonyl Acceptors

Aldehydes

Carboxylic Acid Derivatives

Organohalides

A Proton as the Electrophile

Miscellaneous Transformations Following the Brook Rearrangement

Eliminations

Lithioiminium‐Ion‐Mediated Reactions

Applications to Synthesis

Overview

Total Synthesis of Natural Products

(+)‐α‐Onocerin.

237

(+)‐Spongistatins.

238–241

Zaragozic Acid C.

242

Comparison With Other Methods

Experimental Conditions

Anionic Brook Rearrangements

Counter Ions

Solvents

Additives/Cosolvents

Neutral Brook Rearrangements

Experimental Procedures

2‐(2‐

N

‐Methylpyrroyl)‐1‐phenyl‐2‐triethylsilyloxyethanone [Cyanide‐Catalyzed Cross Silyl Benzoin Reaction of an Acylsilane (Brook Rearrangement of an Acylsilane)].

40,82

tert

‐Butyl‐2‐(

tert

‐Butyldimethylsilyloxy)‐3‐hydroxy‐4‐methylbutanoate [Oppenauer Oxidation/Meerwein–Ponndorf–Verley Reduction‐Induced [1,2]‐Brook Rearrangement of a Silylglyoxylate (Brook Rearrangement of an Acylsilane)].

95

3‐[(

tert

‐Butyldimethylsilyl)oxy]‐6‐pentyl‐5‐(trimethylsilyl)cyclohept‐3‐enone [Formal [4 + 3]‐Annulation of an α,β‐Unsaturated Acylsilane with an Enolate (Brook Rearrangement of an Acylsilane)].

30

(

S

)‐(+)‐Benzyl 2‐cyano‐2‐phenyl‐2‐triethylsiloxyacetate [Asymmetric Cyanation/[1,2]‐Brook Rearrangement/C‐Acylation Reaction of an Acylsilane (Brook Rearrangement of an Acylsilane)].

44,119

(

Z

)‐

N

‐(2‐Oxo‐1,2‐diphenylethylidene)‐

P

,

P

‐diphenylphosphinic amide [Catalytic Addition of an Acylsilane to an Imine (Brook Rearrangement of an Acylsilane)].

45,121

1,2,4‐Triphenylbutane‐1,4‐dione [Thiazolium‐Catalyzed Sila‐Stetter Reaction of an Acylsilane and an α,β‐Unsaturated Ketone (Brook Rearrangement of an Acylsilane)].

42,45

(

Z

)‐

tert

‐Butyldimethyl‐[(7‐phenoxyhepta‐1,3,4‐trien‐1‐yl)oxy]silane [Meerwein–Ponndorf–Verley–Type Reduction/Brook Rearrangement/Protonation of an Acylsilane (Brook Rearrangement of an Acylsilane)].

131

(

Z

)‐3‐Phenyl‐3‐[(triethylsilyl)oxy]‐2‐(trimethylsilyl)prop‐2‐en‐1‐ol [Addition of a TMS‐Substituted Oxiranyl Anion to an Acylsilane (Brook Rearrangement of an Acylsilane)].

37

(

Z

)‐3‐[Phenyl(trimethylsilyl)methylene]chroman‐4‐one [Photochemically Induced Intramolecular Silylacylation of an Alkyne with an Acylsilane (Brook Rearrangement of an Acylsilane)].

152

1‐(2‐Vinylphenyl)pentan‐1‐ol [Pd‐Mediated Cross‐Coupling of 2‐(Trimethylsilyl)benzaldehyde and Vinyl Bromide (Brook Rearrangement of a Keto Silane)].

161

(

E

)‐2,4‐bis[(

tert

‐Butyldimethylsilyl)oxy]‐2‐methylbut‐3‐enenitrile [Sequential Base‐Promoted Ring‐Opening/Brook Rearrangement/Allylic Alkylation Reaction (Brook Rearrangement of an Epoxysilane)].

171,172

(

Z

)‐2‐(3‐Methyl‐1‐phenethylbut‐3‐ene‐1‐ylidene)‐1‐cyclohexanol [Stereospecific Allylation of a (

Z

)‐γ‐Trimethylsilyl Allylic Alcohol (Brook Rearrangement of a Hydroxysilane)].

195,196

(

R

)‐1‐(Benzyloxy)‐3‐(2‐{(

R

)‐3‐(benzyloxy)‐2‐[(

tert

‐butyldimethylsilyl)oxy]propyl}‐1,3‐dithian‐2‐yl)propan‐2‐ol [Reaction of a Dithiane Anion with a Terminal Epoxide (Brook Rearrangement of a Silyl Carbanion)].

219,221

[(1,2‐Diphenylvinyl)oxy]dimethyl(phenyl)silane [Reduction of an α‐Silyloxy Ketone Using Phenyldimethylsilyllithium (Brook Rearrangement of a Silylmetallic Compound)].

233

Tabular Survey

Chart 1.

Catalysts Used in the Tables

Chart 2.

Ligands Used in the Tables

Table 1A.

Brook Rearrangement of Acylsilanes with Aldehydes as Electrophiles

Table 1B.

Brook Rearrangement of Acylsilanes with Ketones as Electrophiles

Table 1C.

Brook Rearrangement of Acylsilanes with Carboxylic Acid Derivatives as Electrophiles

Table 1D.

Brook Rearrangement of Acylsilanes with Imines as Electrophiles

Table 1E.

Brook Rearrangement of Acylsilanes with Electrophilic Alkenes as Electrophiles

Table 1F.

Brook Rearrangement of Acylsilanes with Organohalides and Their Analogs as Electrophiles

Table 1G.

Brook Rearrangement of Acylsilanes with Heteroatom Electrophiles

Table 1H.

Brook Rearrangement of Acylsilanes with Protons as Electrophiles

Table 1I.

Brook Rearrangement of Acylsilanes Followed by Elimination

Table 1J.

Brook Rearrangement of Acylsilanes Followed by Other Miscellaneous Transformations

Table 2A.

Brook Rearrangement of Keto Silanes with Carbonyl Acceptors as Electrophiles

Table 2B.

Brook Rearrangement of Keto Silanes with Epoxides as Electrophiles

Table 2C.

Brook Rearrangement of Keto Silanes with Organohalides and Their Analogs as Electrophiles

Table 2D.

Brook Rearrangement of Keto Silanes with Heteroatom Electrophiles

Table 2E.

Brook Rearrangement of Keto Silanes with Protons as Electrophiles

Table 2F.

Brook Rearrangement of Keto Silanes Followed by Miscellaneous Transformations

Table 3A.

Brook Rearrangement of Epoxysilanes with Carbonyl Acceptors as Electrophiles

Table 3B.

Brook Rearrangement of Epoxysilanes with Electrophilic Alkenes as Electrophiles

Table 3C.

Brook Rearrangement of Epoxysilanes with Epoxides or Aziridines as Electrophiles

Table 3D.

Brook Rearrangement of Epoxysilanes with Organohalides and Their Analogs as Electrophiles

Table 3E.

Brook Rearrangement of Epoxysilanes with Protons as Electrophiles

Table 3F.

Brook Rearrangement of Epoxysilanes Followed by Miscellaneous Transformations

Table 4A.

Brook Rearrangement of Hydroxysilanes with Carbonyl Acceptors as Electrophiles

Table 4B.

Brook Rearrangement of Hydroxysilanes with Electrophilic Alkenes as Electrophiles

Table 4C.

Brook Rearrangement of Hydroxysilanes with Epoxides as Electrophiles

Table 4D.

Brook Rearrangement of Hydroxysilanes with Organohalides and Their Analogs as Electrophiles

Table 4E.

Brook Rearrangement of Hydroxysilanes with Heteroatom Electrophiles

Table 4F.

Brook Rearrangement of Hydroxysilanes with Protons as Electrophiles

Table 4G.

Brook Rearrangement of Hydroxylsilanes Followed by Miscellaneous Transformations

Table 5A.

Brook Rearrangement of Silyl Carbanions with Carbonyl Acceptors as Electrophiles

Table 5B.

Brook Rearrangement of Silyl Carbanions with Electrophilic Alkenes as Electrophiles

Table 5C.

Brook Rearrangement of Silyl Carbanions with Epoxides as Electrophiles

Table 5D.

Brook Rearrangement of Silyl Carbanions with Organohalides and Their Analogs as Electrophiles

Table 5E.

Brook Rearrangement of Silyl Carbanions with Heteroatom Electrophiles

Table 5F.

Brook Rearrangement of Silyl Carbanions with Protons as Electrophiles

Table 5G.

Brook Rearrangement of Silyl Carbanions Followed by Elimination

Table 5H.

Brook Rearrangement of Silyl Carbanions Followed by Other Miscellaneous Transformations

Table 6A.

Brook Rearrangement of Silylmetallic Compounds with Carbonyl Acceptors as Electrophiles

Table 6B.

Brook Rearrangement of Silylmetallic Compounds with Organohalides and Their Analogs as Electrophiles

Table 6C.

Brook Rearrangement of Silylmetallic Compounds with Protons as Electrophiles

Table 6D.

Brook Rearrangement of Silylmetallic Compounds Followed by Elimination

Table 6E.

Brook Rearrangement of Silylmetallic Compounds Followed by Other Miscellaneous Transformations

References

Introduction

The Brook rearrangement describes the intramolecular silyl group migration from a carbon to an oxygen atom.1–15 It constitutes a well‐known and powerful approach for the functionalization of organosilanes. The research on this rearrangement dates back to the 1950s, wherein Gilman and co‐workers unexpectedly observed an “abnormal” product from the addition of triphenylsilyl potassium to benzophenone (Scheme 1).16–18 A more complete and accurate understanding of the mechanism of this process was not established until a few years later when Brook and co‐workers discovered that the abnormal product arose from a normal addition followed by an intramolecular anionic carbon to oxygen silyl group migration.19 The migratory aptitude of silyl groups in this context was found to be more general when treating various silylcarbinols with base (Scheme 2).20–23 The fascination with this rearrangement has resulted in many significant contributions which comprise a family of intramolecular carbon‐to‐oxygen silyl group migrations now widely recognized as the Brook rearrangement. The notation “[1,n]‐” is used as a prefix to the term “Brook rearrangement” in which “n” refers to the number of chemical bonds between the migrating silicon and the terminal oxygen atom (Scheme 3). The reverse of this process constitutes the intramolecular oxygen to carbon silyl migration, which was first reported by Speier24 and was later systematically studied by West.25 These types of reverse silyl migrations only occur under specific circumstances and are typically referred to as retro‐Brook (or West) rearrangements.

Scheme 1

Scheme 2

Scheme 3

The Brook rearrangement is associated with a shift of negative charge from oxygen to carbon in a “through‐space” fashion by silyl migration. This feature has been extensively applied to develop numerous useful transformations of diverse organosilanes. Some representative examples include the anionic Peterson olefination;26–29 formal [3 + 2]‐ and [4 + 3]‐annulations to construct diverse ring systems;30–33 the synthesis of configurationally defined silyl enol ethers;34–37 multi‐component reactions through a Brook rearrangement based ARC (anion relay chemistry);9,10 and various umpolung processes such as silyl benzoin condensations38–41 and sila‐Stetter reactions.42–45

This chapter presents a thorough overview of the Brook rearrangement. The scope is largely confined to anionic and neutral Brook rearrangements featuring carbon‐to‐oxygen silyl migrations. Thus, miscellaneous variants of the Brook rearrangements such as silyl migration between carbon and nitrogen, carbon and sulfur, silicon and oxygen, and sulfur and oxygen are not covered in this chapter. The retro‐Brook rearrangement is only discussed in the Mechanism and Stereochemistry section where it is deemed appropriate. The examples of [1,3]‐Brook rearrangement based anionic Peterson olefinations, which should be treated as a separate topic, are not covered in the chapter. A number of Hiyama–Denmark cross‐coupling reactions, which involve an exocyclic C–Si bond cleavage of cyclic silicates are also not covered. The tables cover the literature through 2019.

Mechanism and Stereochemistry

The Anionic Brook Rearrangement

Mechanism

The general mechanistic profile of the Brook rearrangement is outlined in Scheme 4. Silyl migration between alkoxide 1 and carbanion 3 is proposed to be an equilibration achieved through the endocyclic C–Si bond cleavage of pentacoordinate silicate 2. This intermediate has been investigated by DFT calculations46 and has even been isolated as a stable compound in some studies, which confirms its existence (Scheme 5).47–50 The greater strength of the oxygen–silicon bond (120–130 kcal mol–1) compared to the carbon–silicon bond (75–85 kcal mol–1) is suggested to drive the direction of this equilibrium towards 3 (i.e., the Brook rearrangement). When an anion‐stabilizing group is located on the carbon α to the silyl group, the Brook rearrangement can be facilitated as the result of forming a stabilized carbanion. Lithium alkoxides, which are typically aggregated in ethereal solvents and possess tight ion pairing characteristics, disfavor the silyl migration from 1 to 3 in [1,4]‐ and higher‐order silyl migrations. Thus, polar aprotic solvents such as HMPA, DMPU, or DMF, which can activate the alkoxide by solvating the lithium ions, are frequently used to shift the equilibrium in favor of carbanion 3.

Scheme 4

Scheme 5

The relative propensity for silyl migration generally follows the order of [1,2] > [1,3] > [1,4] > [1,5] > [1,6], which is consistent with the notion that shorter transfer distances are more favorable.51–54 The lower efficiency of higher‐order silyl migrations (e.g. [1,5] and [1,6]) may be attributed to the difficulty in forming an entropically less favorable larger‐ring transition state. Many studies provide evidence suggesting that typical Brook rearrangements (n = 2–4) and even the long‐range [1,5]‐variants55,56 proceed by an intramolecular silyl migration. However, [1,6]‐Brook rearrangements occur in part by an intermolecular pathway. As delineated in Scheme 6, a crossover experiment involving a mixture of 4 and 5 (1:1) produces the crossover product 6 in 24% yield.55

Scheme 6

The general migratory aptitude of the silyl groups follow the following order, namely, SiMe2Ph > TMS > SiMePh2 ≈ TBS.07,57,58 The phenyl ring is proposed to have a stabilizing effect on the migrating silyl group, and this electronic effect compensates for the steric hindrance. However, an additional phenyl substituent decreases the rate of silyl migration because the increased bulkiness overrules the favorable electronic effect. For all‐alkyl‐substituted silyl groups, the migration rate is mainly dependent on the steric hindrance: TMS > TES.59

Stereochemistry

The [1,2]‐Brook rearrangement, in which the migrating silicon moiety is chiral, proceeds with retention of the configuration at the silicon center. This stereochemical course has been determined01,60 using Sommer's chiral hydrosilane.61 As shown in Scheme 7, the (+)‐α‐silyl carbinol, generated from (+)‐l‐NpPhMeSi*H, undergoes sodium‐potassium‐anion‐catalyzed Brook rearrangement to furnish the silyl ether product 7. Subsequent reduction with LiAlH4 provides almost enantiomerically pure (–)‐l‐NpPhMeSi*H. Because the stereochemical course of each step is known, with the exception of the silyl migration, the observed configurational inversion of the hydrosilane produced by this sequence is attributed to silyl migration in a highly stereospecific manner with retention of the silicon configuration (Scheme 7). The retention of configuration in the migration is consistent with a "front side" attack by oxygen at silicon to form a pentacoordinate silicate.

Scheme 7

Inversion of the configuration at carbon was observed by Mosher and co‐workers in the [1,2]‐Brook rearrangement of oxygen‐deuterated (R)‐(+)‐phenyltriphenylsilylcarbinol (9), which was prepared from silylcarbinol 8 by exchange with D2O (Scheme 8).62 In the presence of triethylamine, silylcarbinol 9 rearranged to produce (S)‐(+)‐benzyl‐α‐d triphenylsilyl ether 10 in a quantitative yield. Subsequent reduction with LiAlH4 afforded enantioenriched (S)‐(+)‐benzyl‐α‐d alcohol 11, indicating that the configuration at the carbon center of the carbinol is reversed during the silyl migration. A similar stereochemical outcome was also detected by Brook and co‐workers using (R)‐(+)‐l‐NpPhMeSi‐substituted phenylcarbinol.63

Scheme 8

However, if the phenyl substituent on the stereogenic carbon center is replaced by an alkyl group, retention of the configuration is either observed64–67 or inferred.68For example, treatment of the cis and trans α‐hydroxysilanes in Scheme 9with 5 mol % t‐BuOK in 19:1 DMSO/H2O at room temperature provides the cis‐ and trans‐2‐methylcyclohexanols, respectively. These results strongly indicate that the configuration of the carbon center is retained during silyl migration (Scheme 9).64

Scheme 9

The Neutral Brook Rearrangement

Radical‐Type Silyl Migrations

The Brook rearrangement of silyl alkoxyl radicals is related to or reminiscent of the anionic version. Ab initio molecular‐orbital calculations predict that the intramolecular [1,2]‐silyl migration of 12 proceeds through a front‐side mechanism involving the transition state 13, which adopts a tetrahedral arrangement of the ligands rather than a trigonal bipyramidal hypervalent structure (Scheme 10).69 This geometry also suggests that if the chiral silicon migrates, the configuration of silicon would be expected to be retained.69 In some 5‐exo and 6‐exo radical type cyclizations, the silyl migration is suggested to be most likely irreversible because of the strength of the O–Si bond.70 The resulting silyl alkoxyl radical 14 typically undergoes hydride abstraction.71 This intermediate can also be trapped intramolecularly by another radical to produce a cyclopropane.72

Scheme 10

Concerted‐Type Silyl Migration

Under thermal73 or photochemical74 activation, acylsilanes undergo a [1,2]‐Brook rearrangement to produce a siloxycarbene species. The intrinsic reaction coordinate (IRC) calculation predicts that the thermal silyl migration in an acylsilane proceeds through transition state 15