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Quaternary Stereocenters. Challenges and Solutions for Organic Synthesis. Edited by Jens Christoffers and Angelika Baro

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Quaternary Stereocenters
Challenges and
Solutions for
Organic Synthesis.
Edited by Jens
Christoffers and
Angelika Baro.
Wiley-VCH, Weinheim 2005. 336 pp.,
hardcover
E 139.00.—ISBN
3-527-31107-6
Is number four the winner? The stereoselective synthesis of quaternary carbon
atom centers is one of the most challenging tasks of organic chemistry. Of
the many synthetic methods that are
nowadays available, only a relatively
small fraction can be confidently relied
on to overcome this fundamental obstacle of chemical synthesis. In addition to
those, however, there also exist many
individual approaches that may have
been devised as a part of a specific
synthetic project. Work on the development of methods and on targeted syntheses has generated a broad spectrum
of such alternatives, with a richness and
variety that even the insider finds it
increasingly difficult to grasp. There has
long been a clear need for an up-to-date
and well-structured survey of the problem, both as a reference source and as an
introduction for beginners. Now, at last,
that gap has been filled by the publication of this monograph.
The title Quaternary Stereocenters
will perhaps give rise to some disagreement, as purists of synthetic chemistry
will insist that a quaternary carbon atom
normally means one that carries four
other carbon atoms as substituents (an
all-carbon quaternary center). The edi-
540
tors of this book have decided that it
should also cover other carbon centers
with four substituents other than hydrogen, in which a carbon atom as substituent is replaced by a functional group
(e.g., as in a tertiary alcohol or tertiary
amine). However, readers may think it
unfortunate that these fundamentally
different structural elements are not
treated consistently by the authors of
the chapters, but receive varying levels
of attention and emphasis. The introductions to several of the chapters show
that their authors disagree considerably
about the meaning of the term quaternary, despite the fact that it is clearly
defined!
However, an examination of the
actual contents of the book shows that
the editors have succeeded well in
assembling a collection of articles on
the different topics to give a clear overall picture. The material is arranged
according to classes of reactions
(broadly grouped under rearrangements
and free-radical reactions) and, where
appropriate, according to key reactions
(e.g., aldol reactions and Michael additions). Separate chapters on specific
topics (syntheses of natural products
and of drugs) are also included, and
the editors wisely chose these as introductory chapters, as they provide an
ideal context in which to illustrate the
state of the art in the synthesis of
quaternary stereocenters, and also its
limitations.
In Chapter 1, H. Arimoto and D.
Uemura describe a number of very nice
total syntheses of polycyclic natural
products. The authors have arranged
these according to reaction types, but in
doing so they have fortunately largely
avoided any overlapping with discussions in other chapters. Their choice of
subjects is certainly personal rather than
comprehensive, but that makes this part
of the book suitable for dipping into as
bedtime reading. Chapter 2, by J. G.
de Vries, gives the reader an interesting
insight into industrial methods for the
synthesis of drugs and important intermediates. It is especially interesting that
biosynthetic methods are now used
almost exclusively for the synthesis of
products based on quaternary carbon
centers with four other carbon substituents, as this offers the only economical
route.
+ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
In Chapter 3, B. Schetter and R.
Mahrwald cover the many different
facets of aldol reactions controlled by
the substrate and catalyst. Unfortunately, the authors have not divided
their discussion clearly between quaternary stereocenters (trisubstituted enolate equivalents and aldehydes) and
tertiary alcohols (enolate equivalents
and ketones). In Chapter 4 the editors,
J. Christoffers and A. Baro, contribute
an excellent article on stereoselective
Michael reactions and conjugate addition reactions of methylene-active compounds and enamines.
Two chapters deserve to be especially mentioned because of their “student-friendly” character. In Chapter 5,
A. Pollex and M. Hiersemann summarize the applications of rearrangements,
and in Chapter 11 K. Patil and M. P. Sibi
deal with free-radical reactions. The
graphics in these chapters (showing
transition states, and using Newman
projections) are excellent from a didactic standpoint, and help the reader to
quickly grasp the nature of the underlying mechanisms and the stereoselectivities involved. The extensive subject
of cycloadditions ([2 + 1], [2 + 2], Diels–
Alder, and 1,3-cycloadditions) is also
very well covered in Chapter 6, by G.
Desimona and G. Faita.
The topic of palladium-catalyzed
reactions is treated in Chapter 7, by L.
Barriault and E. L. O. Sauer (Heck
reactions and cross-couplings), and in
Chapter 9 by M. Braun (allylic alkylations). Reactions of other electrophiles,
as well as nucleophilic allylations, are
discussed in detail.
Two chapters are devoted to the
stereoselective synthesis of heteroatomsubstituted quaternary carbon centers.
In Chapter 8, D. J. RamFn and M. Yus
describe methods for the alkylation of
ketones and imines; however, the chapter would have been even more useful if
it had included asymmetric 1,2-addition
of carbon nucleophiles to ketones and
imines. In Chapter 12 (the last), U. T.
Bornscheuer, E. Henke, and J. Pleiss
give a short description of enzymatic
methods for the asymmetric synthesis of
sterically-hindered tertiary alcohols.
In Chapter 10, T. Ooi and K. Maruoka give a really excellent survey of
asymmetric reactions of C H-acidic
Angew. Chem. Int. Ed. 2006, 45, 540 – 542
Angewandte
Chemie
compounds with an acidic hydrogen
atom) by using phase-transfer catalysis.
The reader who searches diligently
for shortcomings in any book, however
carefully it has been edited and checked,
will certainly manage to find a few, and
that is also the case here. One criticism is
that a glossary of abbreviations common
to all the chapters would have been
desirable. Also, the work has the weakness that is now common in many books,
namely that the index needs improvement. For example, desymmetrization
reactions, which are mentioned in many
of the chapters, have not found their way
into the index. However, that is essentially the full extent of the criticisms, as
the presentation of the material is very
good throughout, leaving aside the
rather vague definition of a quaternary
stereocenter.
This book will be an excellent addition to the collections of chemistry
departmentsJ libraries. Not only graduate students but also leaders of research
groups will benefit from reading it, and
will also enjoy simply dipping into it.
Number four is the winner!
Martin Oestreich
Institut f2r Organische Chemie und
Biochemie
Albert-Ludwigs-Universit6t
Freiburg im Breisgau (Germany)
DOI: 10.1002/anie.200585353
Elegant Solutions
Ten Beautiful
Experiments in
Chemistry. By Philip
Ball. Royal Society
of Chemistry, Cambridge 2005.
212 pp., hardcover
£ 19.95.—ISBN
0-85404-674-7
To many chemists, their discipline is not
only a science, it is also an art. This
creative power was introduced by the
French chemist Marcelin Berthelot as
early as 1860, by stating “La chimie crKe
Angew. Chem. Int. Ed. 2006, 45, 540 – 542
son object” (“chemistry creates its
object”). Like the artist, the chemist
discovers and often invents original
processes and molecules shaped and
decorated with a particular aesthetic
quality. But how and where does
beauty reside in chemical experiments?
This difficult question constitutes the
core of this new book by Philip Ball, a
scientific writer and consultant editor
for Nature, who has become a prolific
and innovative popularizer of chemistry.
In fact, I cannot think of anyone else
who is able to present this chemical
history tour with such precision and
clarity as Ball achieves. Previous works
include, among others, Lifes Matrix: A
Biography of Water; Stories of the Invisible: A Guided Tour of Molecules;
Bright Earth: Art and the Invention of
Color, and The Ingredients: A Guided
Tour of the Elements. Ball has even
thoroughly explored theoretical ideas, in
both the physical and social sciences
(Critical Mass: How One Thing Leads to
Another).
In Elegant Solutions, Ball offers ten
suggestions for what may be called
beautiful experiments. There is an introductory chapter that I found most
appealing, which tries to answer the
questions “what is an experiment?” and
“what is beauty?”. He begins with a
remarkable (probably unknown to readers) experiment that was conducted by
Sir Francis Bacon (1561–1626). In order
to work out whether snow would delay
putrefaction, he stopped his carriage,
purchased a hen, and stuffed it with
snow (the erroneous theory of spontaneous generation of living organisms
was only disproved later by Pasteur).
Bacon caught a severe bronchitis that
caused his death within a few weeks.
BaconJs major work, Novum Organum,
is then used by Ball as starting point on
inductive reasoning and the planning of
experiments, in contrast to the approach
of the alchemists. These introductory
remarks recognize that beauty can be
expressed in terms of simplicity, elegance, patience, or imagination, which
are employed as useful metaphors
throughout the book. Ball distinguishes
clearly between experiment and discovery, the former characterized by its
conception, execution, and result. In
this context, serendipity is not highlighted as a leitmotiv of beauty, but
rather as another factor that requires a
prepared mind.
The subsequent chapters provide a
well-balanced mixture of history and
chemistry, a journey in which the author
transports us from the earliest beginnings of chemistry to the latest in
molecular complexity and quantum
transmutation. Chapter 1 is devoted to
the Flemish alchemist Jan Baptista van
Helmont (1579–1644) and his famous
tree experiment, to prove that water was
the chief constituent of matter. With the
addition of nothing but water over a
five-year period, a willow tree increased
in weight by 164 pounds, whereas the
soil weight decreased by only a few
ounces. We now know that van Helmont
was wrong; however, he was a careful
observer and exact experimenter, who
anticipated the law of conservation of
matter. Water is also at the core of
Chapter 2, on the life and achievements
of Henry Cavendish, who discovered
that water is a compound, not an
element, and thought he had captured
phlogiston (hydrogen) in a bottle. The
isolation of radium and polonium by
Marie and Pierre Curie is the subject of
Chapter 3. It may be dubious to call
their long and arduous work elegant.
However, the discovery of such radioactive elements demonstrated a beauty
of spirit and perseverance. The chapter
that follows describes in detail the
experiments conducted by Rutherford,
who conclusively demonstrated the
nature of the mysterious radiation that
emanated from radioactive elements.
Thus, he found the modern “PhilosopherJs stone”, paving the way for the
isolation of artificial superheavy elements, an achievement exemplified in
Chapter 5, which describes the isolation
of seaborgium. PasteurJs mechanical
resolution of tartrate enantiomers
(Chapter 6) was elegantly simple, and
there is no doubt that crystalline materials are inherently beautiful. This
experiment was selected by the readership of Chemical & Engineering News,
the official ACS magazine, as the most
memorable experiment in the history of
chemistry (C&EN 2003, Aug. 25, p. 27).
Chapter 7 deals with the crucial Urey–
Miller experiment that generated compounds essential for the formation of
living matter from a mixture of gases
and water, which might have existed on
+ 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
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