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Book Review Microwaves in Organic Synthesis Edited by Andr Loupy.

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cost and applicability. I cannot really see
graduate students wanting to perform
them either, because they may find them
a bit dry and, with a few exceptions, not
particularly relevant. I think this chapter
could have done with more thought in
writing the second edition of the book,
since many of the experiments are
reproduced directly from the first edition. It would have been nice to see this
chapter increased in size with, perhaps,
reactions classified in categories with
representative examples of each,
together with some thought-provoking
examples from the recent literature.
Although on the whole the book is
well-written (perhaps with the exception
of the final chapter), it is let down
considerably by the layout and presentation. As mentioned earlier, the text is
very small and densely packed onto the
pages. This makes reading rather hard
going at times. Also, there are lots of
photographs of apparatus in the book,
all in black and white, the quality of
which is on the whole not good. These
would have been so much better if color
had been used. With modern technology
that should be possible. It would also
have enhanced the figures and schemes
considerably. The figures could also
have done with a bit more artistic
licence. It looks as though they were
scanned in from those submitted by the
authors, who are scientists not professional artists. All in all, the presentation
in the book is a bit drab and uninspiring.
On the plus side, each of the chapters
ends with a useful list of references to
both books and primary literature sources for further reading.
In summary, the book offers a useful
introduction to the principles of ultrasound and its applications to practical
chemistry. It includes a useful discussion
of commercially available apparatus,
and also addresses scale-up issues. The
practical examples are not ideal, but
taken as a whole I would recommend
the book to university libraries as a
useful addition.
Nicholas E. Leadbeater
Department of Chemistry
King’s College London
London (Great Britain)
2334
Microwaves in Organic Synthesis
Edited by André
Loupy. WileyVCH, Weinheim
2002. 524 pp.,
hardcover
E 159.00.—ISBN
3-527-30514-9
Microwave-assisted synthesis is an area
of increasing research interest as evidenced by the number of papers and
recent reviews appearing in the literature. As well as being energy efficient,
microwaves can also enhance the rate of
reactions and in many cases improve
product yields. The book edited by
André Loupy brings together contributions from a collection of world experts
in the field of microwave-promoted
organic synthesis, ranging from those
who were instrumental in the initial
development of the technique through
to people developing new ideas based
around microwave chemistry. The book
comes at a timely point, is well-written,
and is a valuable addition to the library
of synthetic chemists working in both
academia and industry.
The first chapter addresses some of
the physical concepts of microwave
chemistry as well as introducing some
of the modern equipment used. This is
written in a style which is easily accessible by synthetic chemists who have
little or only rusty physical chemistry
background. Much of the work in the
field of microwave-assisted synthesis has
been carried out using modified domestic microwave ovens. However, there
are problems associated with this, in
particular poor reproducibility of reactions and the fact that it is hard to
control the reaction precisely. With the
advent of scientifically focused microwave systems, many of these problems
can be overcome. There is a brief
discussion of the main commercial
microwave reactors for both smallscale and industrial use. My feeling is
that this could have been expanded,
since this is very valuable information to
chemists who are considering embark-
0 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
ing on a programme of work in the
field.
Following on from this introduction,
there are a number of chapters from
synthetic chemistry groups who present
aspects of their work in the microwave
chemistry field as well as reviewing
other contributions in the area on
which they are focusing. Some of the
topics discussed are metal-mediated
catalysis, radiochemistry, and combinatorial chemistry using microwaves, the
use of pressurized reactors for performing microwave chemistry, microwavepromotion in heterocyclic synthesis, in
cycloaddition chemistry, and in phasetransfer catalysis, and microwaveassisted organic synthesis both in homogeneous media and with supported
reagents. In short, there is something
for everyone. On the whole these chapters are well-written and bring together
much of the work undertaken in the
field. They are illustrated with lots of
examples that provoke new ideas, and
would certainly act as a good starting
point for anyone wishing to become
familiar with the field. Also the work
presented is useful for people already
involved in microwave chemistry. My
only criticism would be that some of the
chapters seem to have been simply
modified from reviews previously written by the authors in chemistry journals.
That is rather unfortunate, but, having
said this, the advantage of this book is
that all the information is in one place,
and often chemists do not have immediate access to all the chemistry journals
in which the sections have previously
appeared in some form.
There is a chapter on the somewhat
controversial issue of nonthermal effects
of microwaves in organic synthesis.
Since the start of research on microwave-assisted synthesis, reaction rates
much higher than those using “conventional” heating have been reported, and
this has sparked debate about the nature
of the microwave heating. The acceleration of reactions could simply be an
effect of the thermal energy generated
by the microwaves interacting with the
substrates, or it could be an effect
specific to microwave heating. In most
cases the observed differences between
microwave and conventional heating
can be attributed to simple thermal
effects. In their chapter, Loupy and
Angew. Chem. Int. Ed. 2003, 42, 2331 – 2335
Angewandte
Chemie
Perreux address the issue and propose a
rationalization of microwave effects in
organic synthesis based on solvent
effects and also on mechanistic considerations. They suggest that if the polarity
of a system is enhanced from the ground
state to the transition state, it can result
in an acceleration of the reaction as a
result of an increase in the interaction
between the microwaves and the material during the course of the reaction.
They also discuss work by other research
groups and suggest that the origin of
microwave effects lies in perturbation of
terms in the Arrhenius equation. Certainly, in our experience of microwavepromoted synthesis, we have not seen
any effects that cannot be rationalized in
terms of efficient thermal heating of the
reaction mixture. With a conventional
heating system such as an oil bath, heat
must be transferred through reaction
vessel walls, whereas microwave promotion allows efficient direct heating of the
sample itself. This internal heat transfer
minimizes wall effects (no thermal
boundary layer), and reaction mixtures
Angew. Chem. Int. Ed. 2003, 42, 2331 – 2335
can be heated to high temperatures
rapidly and very efficiently. The issue
will no doubt remain a hot topic for
discussion.
The final two chapters of the book
are devoted to microwave-promoted
radiochemistry and microwave photochemistry. In radiochemistry, where
molecules have to be made, purified,
and used within the period of a few
lifetimes of the radiolabeled constituents, microwave chemistry can have a
big advantage, since it is possible to
prepare compounds rapidly using microwave promotion. Despite this, the technique has not attracted the attention one
may have expected within the synthetic
chemistry community. In their chapter,
Jones and Lu mainly address the use of
microwaves in the preparation of
longer-lived tritium- and deuteriumlabeled compounds. Following this,
there is a brief discussion of compounds
containing the shorter-lived isotopes 11C
and 18F (lifetimes of 20.4 min and
110 min, respectively). In their chapter
Klán and C7rkva discuss the area of
www.angewandte.org
microwave
photochemistry.
This,
together with other combinations of
microwaves with techniques such as
ultrasound and grinding, promises to
be an area of increased research activity
in the future and so is a fitting end to the
book.
In summary, the book offers a useful
introduction to the area of microwaveassisted organic synthesis as well as
being a valuable research tool. It offers
an insight into a wide range of uses and
applications of microwaves in synthesis,
and the combination of discussion and
illustrative examples is well-balanced in
most chapters. In addition the large
number of citations in all chapters
stimulates further reading. I certainly
will be recommending it to my graduate
students.
Nicholas E. Leadbeater
Department of Chemistry
King’s College London
London (Great Britain)
0 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2335
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