C. Rojas – Molecular Rearrangements in Organic Synthesis (2015)

Автор: C. Rojas
Название книги: Molecular Rearrangements in Organic Synthesis
Формат: PDF
Жанр: Химия
Страницы: 955
Качество: Изначально компьютерное, E-book

Designed for practitioners of organic synthesis, this book helps chemists understand and take advantage of rearrangement reactions to enhance the synthesis of useful chemical compounds.

Provides ready access to the genesis, mechanisms, and synthetic utility of rearrangement reactions
Emphasizes strategic synthetic planning and implementation
Covers 20 different rearrangement reactions
Includes applications for synthesizing compounds useful as natural products, medicinal compounds, functional materials, and physical organic chemistry

There is an aesthetically pleasing quality – a Kekuléan snake-seizing-its-tail appeal – to
molecular rearrangements. A chemist using the arrow-pushing formalism to outline a
rearrangement reaction feels a certain tactile satisfaction in charting the electron flow, an
aspect that makes these reactions fun for instructors to teach or for students to work through at
the blackboard. Rearrangements often have perfect atom economy, satisfying the frugal: bonds
reorganized and nothing wasted. In some cases, a small molecule or other appropriate leaving
group is extruded, initiating the rearrangement; sometimes, a catalyst is involved. Whatever the
details, molecular rearrangements possess an inherent elegance that makes them especially
appealing to students and practitioners of organic chemistry.
But molecular rearrangements do not just satisfy the intellect; they are irreplaceable tools in
getting the work of organic chemical synthesis done. Different types of rearrangements enable
synthetically useful operations, including ring expansions as in certain Beckmann
rearrangements, ring-contracting reactions (e.g., the quasi-Favorskii and Ramberg–Bäcklund
rearrangements), and functional group transpositions as occur in Payne and Mislow–Evans
rearrangements. Another synthetically essential hallmark of many rearrangements is their
stereospecificity, providing, as in the Claisen rearrangement, a means to parlay more readily
established stereochemical features of the starting material into product stereochemistry that
might otherwise be difficult to access.
How to group different molecular rearrangements? There is an understandable desire to
classify and categorize, to find common themes, but there are many possible points of
comparison. One could focus on functionality within the starting material, the type of product
accessible via the rearrangement, or the reaction mechanism. To a certain extent, however, any
categorization scheme is idiosyncratic and imperfect. For example, mechanistic categorization
can be difficult for certain reactions, such as the vinylcyclopropane–cyclopentene
rearrangement, which may have mechanistic variants, including radical, ionic, or metalcatalyzed
versions. In this book, rearrangements are sorted mainly by changes in connectivity
during the reaction: 1,2-migrations, 1,3-transpositions, or ipso rearrangements. However,
sigmatropic rearrangements of differing order, [3,3] versus [2,3], are grouped together as a
mechanistic category so as to hew to tradition and not confound the reader.
The purpose of this book is to provide readers with a clear and interesting point of departure
for thought and further investigation. There is a clear focus on synthetic utility, analyzing how
rearrangement reactions can meet challenges in the synthesis of complex molecular structures,
including biologically active natural products. Importantly, the chapters are not intended as
comprehensive reviews, and each is rendered in a distinctive voice. Some chapters take a
broad outlook, while others concentrate on the authors' own contributions. Some chapters are
more limited to the recent literature, while others provide historical context and discuss
seminal studies in addition to current examples. By highlighting key examples and describing
recent progress in the field, this book aims to help stimulate creative rearrangement-mediated solutions to contemporary challenges in synthetic organic chemistry.
In the realization of this volume, I am indebted foremost to the chapter authors for their
willingness to participate in the project and their insightful, thorough treatment of the
rearrangement topics. I am also grateful to Jonathan Rose, my editor at Wiley, for his patient
guidance in completion of the book. Finally, I thank Ms. Jenny Lam for her invaluable
assistance in compiling the manuscript components.
Christian M. Rojas
Barnard College
New York, NY
March 2015