JOHN E. BALDWIN PETER BEAK DALE L. BOGER ANDRÉ B. CHARETTE ENGELBERT CIGANEK DENNIS CURRAN SAMUEL DANISHEFSKY HUW M. L. DAVIES SCOTT E. DENMARK JOHN FRIED JACQUELYN GERVAY‐HAGUE HEINZ W. GSCHWEND STEPHEN HANESSIAN LOUIS HEGEDUS PAUL J. HERGENROTHER JEFFREY S. JOHNSON ROBERT C. KELLY LAURA KIESSLING |
MARISA C. KOZLOWSKI STEVEN V. LEY JAMES A. MARSHALL MICHAEL J. MARTINELLI STUART W. MC COMBIE SCOTT J. MILLER LARRY E. OVERMAN T. V. RAJANBABU HANS J. REICH JAMES H. RIGBY WILLIAM R. ROUSH TOMISLAV ROVIS SCOTT D. RYCHNOVSKY MARTIN SEMMELHACK CHARLES SIH AMOS B. SMITH, III BARRY M. TROST PETER WIPF |
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 | JAMES D. WHITE |
P. ANDREW EVANS, Editor‐in‐Chief
STEVEN M. WEINREB, Executive Editor
JEFFREY AUBÉ | JEFFREY N. JOHNSTON |
DAVID B. BERKOWITZ | JOHN MONTGOMERY |
PAUL R. BLAKEMORE | ALBERT PADWA |
REBECCA L. GRANGE | JENNIFER M. SCHOMAKER |
DENNIS G. HALL | KEVIN H. SHAUGHNESSY |
DONNA M. HURYN | CHRISTOPHER D. VANDERWAL |
JEFFREY B. JOHNSON |
BARRY B. SNIDER, Secretary
JEFFERY B. PRESS, Treasurer
DANIELLE SOENEN, Editorial Coordinator
DENA LINDSAY, Secretary and Processing Editor
LANDY K. BLASDEL, Processing Editor
DEBRA DOLLIVER, Processing Editor
ENGELBERT CIGANEK, Editorial Advisor
JAMES R. GREEN | |
UROŠ GROŠELJ | |
KENNETH M. NICHOLAS | |
JURIJ SVETE | |
YOSHIHIKO YAMAMOTO |
P. ANDREW EVANS, Editor‐in‐Chief
STEVEN M. WEINREB, Executive Editor
JEFFREY AUBÉ | JEFFREY N. JOHNSTON |
DAVID B. BERKOWITZ | JOHN MONTGOMERY |
PAUL R. BLAKEMORE | ALBERT PADWA |
REBECCA L. GRANGE | JENNIFER M. SCHOMAKER |
DENNIS G. HALL | KEVIN H. SHAUGHNESSY |
DONNA M. HURYN | CHRISTOPHER D. VANDERWAL |
JEFFREY B. JOHNSON |
BARRY B. SNIDER, Secretary
JEFFERY B. PRESS, Treasurer
DANIELLE SOENEN, Editorial Coordinator
DENA LINDSAY, Secretary and Processing Editor
LANDY K. BLASDEL, Processing Editor
DEBRA DOLLIVER, Processing Editor
ENGELBERT CIGANEK, Editorial Advisor
JAMES R. GREEN | |
UROŠ GROŠELJ | |
KENNETH M. NICHOLAS | |
JURIJ SVETE | |
YOSHIHIKO YAMAMOTO |
Copyright © 2020 by Organic Reactions, Inc. All rights reserved.
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Library of Congress Cataloging‐in‐Publication Data:
ISBN: 978‐1‐119‐65125‐3
Printed in the United States of America
10 9 8 7 6 5 4 3 2 1
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.
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.
Serendipity: The faculty or phenomenon of making fortunate discoveries by accident
Horace Walpole, 1754
The serendipitous discovery of a new phenomenon has inspired scientists for centuries and is arguably responsible for countless important and groundbreaking discoveries. The word “serendipity” itself has a rather unusual origin, having been coined by Horace Walpole based on his interpretation of a Persian fairytale, called The Three Princes of Serendip. Nevertheless, this principle has inspired the evolution of the so‐called Scientific Method, in addition to promoting new strategies to improve the chances of making such unexpected discoveries. Irrespective of the origin of this word, when the British chemist Humphrey Davy accidentally discovered acetylene in 1836 while trying to isolate potassium metal by heating potassium carbonate with carbon at very high temperatures: he could never have imagined the impact this discovery would have on synthetic organic chemistry. The aforementioned reaction provided a residue known as potassium carbide, which reacts with water to generate acetylene gas. The French chemist Marcellin Berthelot later discovered an alternative method for its preparation and called the gas acétylène. The notion of finding different ways to prepare the same compound is now a foundation of modern synthetic chemistry and represents the very essence of Organic Reactions, which is a preeminent reference for the synthetic organic chemistry community. In this volume, the three seemingly different themed chapters all employ alkynes in different ways; however, each serves to illustrate the importance of Davy's original discovery, by taking advantage of the unique orbital symmetry, and the associated reactivity, to provide orthogonal chemical behavior that illustrates the chameleon‐like character of alkynes.
The first chapter by Yoshihiko Yamamoto is an excellent treatise on the preparation of arylalkenes via the transition‐metal‐catalyzed alkyne hydroarylation with arylmetals and aryl halides. Although arylalkenes can be prepared by a classical Friedel‐Crafts acylation, followed by functional group interconversions, these processes were later superseded by the formal C‐H hydroarylation of alkynes. Nevertheless, the lengthy reaction sequences needed in the former process, coupled with the challenges with attaining chemo‐, site‐, and stereoselectivity with both strategies, have prompted the development of methods of generating such products by indirect strategies that employ arylmetal reagents as donors. This chapter delineates the renaissance in this approach following a hiatus after the original report by Duboudin and Jousseaume on the nickel‐catalyzed hydroarylation of internal alkynes and propargylic alcohols with arylmagnesium bromides. Additionally, the disadvantage of using reactive arylmetal intermediates is addressed by the alternative method that employs aryl halides in Heck‐type additions, which was pioneered by Cacchi and coworkers. Hence, the chapter is ordered according to the scope of the aromatic component and its role in the reaction, namely, alkyne hydroarylations using arylmetal reagents (alkyne carbometallation/protonation) and aryl halides (reductive Heck reaction). The mechanism, selectivity, scope, and limitations for the two different approaches are logically delineated throughout. For instance, the section on arylmetal reagents outlines examples of the various metals that have been employed (e.g., Li, Mg, Zn, B, Si, and Sn). In contrast, the addition of aryl halides and arenediazonium salts to alkynes is divided into inter‐ and intramolecular reactions, in conjunction with some cascade processes that are based on 1,4‐metal shifts. The Applications to Synthesis section provides excellent examples that showcase some of these processes, which is followed by an inclusive Comparison with Other Methods section. The comprehensive Tabular Survey is primarily organized in terms of the nucleophilic and electrophilic character of the aryl donor reagent in conjunction with the alkyne, which makes identification of the optimal reaction and the associated conditions relatively simple for the reader. Overall, this is an outstanding chapter on an important reaction, which will be invaluable to anyone wishing to prepare arylalkenes in a site‐ and stereodefined manner.
The second chapter by Uroš Grošelj and Jurij Svete provides a detailed account of the historical development of [3+2] cycloadditions with azomethine imines, which are relatively new in comparison with other 1,3‐dipoles. For instance, the first stable azomethine imine was reported by Earl and McKaney; however, it was not until Huigsen and coworkers recognized their dipolar character in a series of [3+2] cycloadditions with alkynes, alkenes, and cumulenes that this area became attractive to synthetic chemists. The chapter subdivides azomethine imines into four general classes, namely, acyclic, in which the dipole moiety is not a part of any cyclic system as well as C,N‐, N,N‐, and C,N,N‐cyclic azomethine imines, in which two or three atoms of the dipole moiety are a part of a cyclic system as the alkene variant. The authors delineate the mechanistic details in the context of concerted, stepwise, and metal‐catalyzed reactions, which include the details of the site‐ and stereochemical preferences in these reactions. The Scope and Limitations section is organized by the type of azomethine ylide used in combination with the requisite dipolarophile, namely, alkynes, alkenes, and related π‐components. The section on Applications to Synthesis provides examples of using the methodology to prepare some important molecules, and the Comparison to Other Methods section delineates the construction of pyrazoles using alternative cycloaddition and cyclocondensation reactions. The Tabular Survey mirrors the Scope and Limitations section, in which the primary rubric is based on the type of azomethine imine applied in conjunction with the requisite dipolarophile, which makes traversing the text and tables effortless based on the reader's specific interest. Overall, this is an important chapter that I believe will be of significant interest to heterocyclic and medicinal chemists.
The third chapter by James R. Green and Kenneth M. Nicholas outlines the discovery and development of propargyl coupling reactions via bimetallic alkyne complexes, the so‐called Nicholas reaction. The early work on metal aryl stabilized benzylic cations inspired Nicholas and Pettit to examine the inherent stability of the propargylic carbocations derived from acetylene dicobalt hexacarbonyl complexes and the ability to formally trap these intermediates. Hence, the stable metal‐complexes of propargylic derivatives provide access to stabilized carbocations that would otherwise be too challenging to employ in conventional synthetic applications. The Mechanism and Stereochemistry section provides details of their structure and reactivity, including the site‐ and stereochemical course of these transformations. Notably, the intricacies of diastereocontrol are delineated based on the type of reactive intermediate, and the section concludes with advances in the enantioselective variants of the reaction. The enantioselective propargylic cation/nucleophile coupling reaction is categorized into three types, namely additions with achiral nucleophiles, diastereoselective additions with chiral complexes, and diastereoselective additions with prochiral nucleophiles, such as enol derivatives and allylsilanes. The Scope and Limitations section is organized in the context of the preparation of bimetallic alkyne complexes followed by inter‐ and intramolecular nucleophile trapping processes, which include both oxidative and reductive decomplexation reactions. The inter‐ and intramolecular reactions are further subdivided by the type of reaction, namely elimination and nucleophilic trapping, in which the latter is subdivided by the type of pronucleophile, for example, hydride, heteroatom, and carbon variants. In addition, there is a section on inter‐ and intramolecular radical couplings and cyclization reactions. Importantly, the chapter permits the reader to determine the current knowledge gaps and limitations within specific classes of reactions, which will undoubtedly inspire further developments in this area. The comprehensive section on the Applications to Synthesis is organized by inter‐ and intramolecular additions, which include radical processes that illustrate the breadth of this process in complex molecule synthesis to provide the reader with an appreciation of the synthetic utility of this process. The Comparison with Other Methods section describes the limitations of direct propargylic displacements and some of the advances with catalytic variants of this type of transformation. The Tabular Survey is organized by methods for preparing both cobalt and molybdenum complexes, followed by tables that parallel the Scope and Limitations section in the context of inter‐ and intramolecular reactions with various pronucleophiles. Overall, this chapter provides the reader with an outstanding perspective on the historical development of this important named reaction and opportunities for further contributions.
I would be remiss if I did not acknowledge the entire Organic Reactions Editorial Board for their collective efforts in steering this chapter through the various stages of the editorial process. I would like particularly to thank John Montgomery (Chapter 1), Jeffrey Aubé (Chapter 2), and Jeffrey B. Johnson (Chapter 3), who each served as the Responsible Editor and marshaled the individual 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 valuable to the practicing synthetic organic chemist.
P. Andrew Evans
Kingston
Ontario, Canada