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Modern Oxidation Methods. Edited by Jan-Erling Bckvall

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Angewandte
Books
Chemie
Modern Oxidation Methods
Edited by Jan-Erling
Bckvall. WileyVCH, Weinheim
2003. 336 pp.,
hardcover
E 139.00.—ISBN
3-527-30642–0
This is a valuable book, which covers
some of the main topics in modern
organic oxidation chemistry. Much
attention is devoted to sustainable
chemistry, in particular to processes
with low environmental impact, using
benign oxidants such as oxygen or
hydrogen peroxide under mild conditions. The individual chapters are wellwritten (with some exceptions) by leading scientists in the fields covered. Each
chapter includes a large number of general and specific literature references.
The title Modern Oxidation Methods
gives a good description of the overall
concept of the book, which also devotes
special attention to green methodology;
this presents challenges not only in
chemistry but in science generally.
Chapter 1 gives a comprehensive
overview of the dihydroxylation of
alkenes catalyzed by OsO4. Some important aspects of these processes are considered, in particular those related to
the cost and toxicity of OsO4, and the
consequent need for catalyst recycling.
The possibility of using O2 and H2O2 as
alternative primary oxidants is emphasized, and the chapter discusses the
question of stereoselectivity, which is
often required in dihydroxylation. Special attention is given to the mechanistic
Angew. Chem. Int. Ed. 2005, 44, 2321 – 2323
aspects, and to how their elucidation has
led to improved reaction systems. Heterogeneous systems and those based on
ionic liquids are also discussed.
In Chapter 2, the necessity of a clean
and efficient catalytic system for the
epoxidation of olefins is discussed.
H2O2 is considered to be the oxidant of
choice, whereas the limitations on the
direct use of O2 are outlined. The most
widely used catalysts are tungsten complexes, and according to the author
some of these have potential for industrial applications (e.g., production of
propylene oxide). Heterogeneous systems that allow easy recycling are
reviewed.
Other catalytic systems based on
manganese and iron complexes are
also discussed. However, catalysis by
MeReO3, which does not offer any particular advantage compared with
cheaper and safer systems, is treated
more fully than it deserves to be.
Chapter 3 is mainly concerned with
the epoxidation of olefins catalyzed by
ketones under metal-free conditions.
This topic is very interesting because of
the possibility of achieving stereoselective epoxidation by using suitable
chiral ketones. Unfortunately, the chapter fails to emphasize key examples that
give an idea of the present state of the
art. Although many examples and
schemes are presented, they are all
rather similar, and are only likely to confuse a reader who is not deeply involved
in stereochemistry.
Chapter 4 reviews new methods for
the oxidation of alcohols, including
some emerging TEMPO-type catalytic
systems. The importance of ruthenium
compounds coupled with TEMPO for
the aerobic oxidation of alcohol is overemphasized: the method requires comparatively severe conditions, whereas
other systems that use cheaper catalysts
under mild conditions give efficient conversion and excellent selectivity. Several
ruthenium-based heterogeneous systems are also described, and some
important copper- and palladium-based
catalytic systems are discussed.
Chapter 5 gives an excellent description of a new and very attractive organocatalyst for oxidation reactions: Nhydrophthalimide. The authors emphasize its advantages compared with conventional methods for performing
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some important transformations, including industrial processes (e.g., production
of adipic acid from cyclohexane and of
terepthalic acid from p-xylene). Unfortunately, the chapter does not mention
some important research contributions
to the understanding of the mechanistic
aspects of this kind of catalysis.
The most important part of Chapter 6 is that concerned with the interesting catalytic activity of low-valent ruthenium salts for the oxidation of alcohols,
amines, amides, and phenols. This
method offers a unique opportunity to
prepare important intermediates for
the synthesis of complex molecules,
including some that are very significant
from a biological point of view. Biomimetic transformations catalyzed by
RuIII are also discussed.
Chapter 7 reviews stoichiometric
methods and other more interesting catalytic and biocatalytic systems for the
selective oxidation of amines and sulfides. Considerable space is devoted to
stereoselective oxidations of sulphides
to sulfoxides, by using classical oxidation procedures in the presence of suitable chiral ligands. The difficult selective
oxidation of sulfides in the presence of
double bonds is described, with several
examples, including some in which flavines are used as catalysts. As in other
parts of the book, there is an emphasis
on procedures in which oxygen and
hydrogen peroxide are used as primary
oxidants.
Chapter 8 contains an excellent
review of catalysis by polyoxometallates, with particular emphasis on sustainable processes in which O2, H2O2,
or N2O is used as a benign oxidant,
and water or an organic medium of
low environmental impact is the solvent.
By varying the polyoxometallate structure it is possible to perform a variety
of oxidation reactions with high selectivity. The fundamental aspects of catalyst
recycling are also discussed.
The first part of Chapter 9 describes
many different processes for the oxidation of carbonyl compounds by stoichiometric reagents. The author concludes
that the environmental aspects of these
oxidation processes need further
improvement. It would have been
useful to follow this with descriptions
of catalytic reactions using benign oxidants.
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
2321
Books
Chapter 10 provides a good example
of an approach to the improvement of
oxidation processes. It describes oxidations that use H2O2 with various manganese compounds as catalysts, and discusses their present limitations and proposed improvements in detail.
Scientific and technological literature can sometimes identify trends that
offer promise for the future. That is particularly true when the topic is closely
related to achieving a better quality of
life. With that in mind, this book represents an excellent contribution towards
encouraging the chemical community
to plan new oxidation processes with
low environmental impact.
Francesco Recupero
Department of Chemistry, Materials,
and Chemical Engineering
Politecnico di Milano
Milan (Italy)
DOI: 10.1002/anie.200485257
Fluorine in Organic Chemistry
By Richard D.
Chambers. Blackwell Publishing,
Oxford 2004.
406 pp., hardcover
£ 99.50.—ISBN
1-4051-0787-1
2004 is a good year for a reader interested in the field of organofluorine
chemistry. Along with Peer Kirchs
Modern
Fluoroorganic
Chemistry
(Wiley-VCH, 2004), the above monograph makes an excellent contribution
to the diverse and rich field. This revised
and updated edition of the original book
Fluorine in Organic Chemistry, first published in 1973 by John Wiley and Sons, is
skillfully crafted by one of the doyens of
the
organofluorine
chemistry,
Richard D. Chambers, to cover the various synthetic and mechanistic facets of
the subject. The foreword is by Nobel
2322
laureate George A. Olah, who is also
an excellent fluorine chemist.
The book is exactly patterned after
the original monograph, with ten chapters (same chapter titles!). The number
of pages of the revised version is
almost similar to that of the original
(391 pp.). This, in a way, restricted the
author from covering newer aspects of
the ever-expanding field. Chapter 1
deals very briefly with the general
aspects of organic fluorine chemistry,
including the use of organofluorine
compounds in materials, medicinal, and
agrochemical
applications.
Some
aspects of PET imaging, as well as biotransformations of fluorinated compounds, are briefly touched on. A short
discussion of the electronic effects of
fluorocarbon systems that make these
applications possible is also presented,
along with the nomenclature of fluorocarbon compounds, including special
nomenclature for CFC, HCFC, and
HFC compounds (Freon and Freon substitutes).
Chapter 2 dwells on the methods for
the preparation of highly fluorinated
compounds, including the use of metal
fluorides, HF, and elemental fluorine.
Along with the addition and displacement reactions, cobalt-trifluoride-based
polyfluorinations of aliphatic and aromatic derivatives, electrochemical fluorinations, and fluorination using elemental fluorine are covered. Various
experimental methodologies, including
the use of microreactors, are described.
The use of halogen fluorides for polyfluorinations is briefly mentioned.
Chapter 3 is concerned with selective and partial fluorination procedures
using a wide variety of synthetic protocols. Applications of silver and alkalimetal fluorides, elemental fluorine as
an electrophile, hypofluorides, N-Ftype onium systems, XeF2, HF and
related onium polyhydrogen fluorides,
SF4, DAST and related systems, etc.,
are briefly covered. Several functional
group transformations to fluorinated
derivatives are succinctly described.
Since this area has a vast amount of literature, brevity certainly does not help
here.
Chapter 4 has a distinct mechanistic
flavor, and describes the influence of
fluorine or fluorocarbon groups on reaction centers. In addition to steric and
2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
electronic effects, the role of electronegative fluorine and perfluoroalkyl substitutents in modulating the strengths (H0
and pKa) of carboxylic and sulfonic
acids, as well as basicity of amines
(pKb), is discussed. The concepts of “fluorine hyperconjugation” in benzotrifluorides and “ fluorine negative hyperconjugation” in carbanions are also discussed. Some discussion on fluorinesubstituted carbocations, fluorocarbanions, and fluorine-substituted carbon
radicals is also presented.
Chapters 5 and 6 are devoted,
respectively, to the various aspects of
nucleophilic displacement of halogen
from fluorocarbon systems, and elimination reactions. In the latter, both b and a
elimination reactions are covered. The
preparation and reactions of fluorosubstituted carbenes are also included.
Some structural aspects fluorocarbenes
and polyfluoroalkylcarbenes are discussed.
Chapter 7 covers most aspects of
polyfluoroalkanes, -alkenes, -alkynes,
and derivatives. The defluorination and
functionalization of polyfluoroalkanes
(and polyfluorocycloalkanes) using
alkali-metal fusion or reactions with
alkali-metal complexes are described.
Such electron-transfer reactions can
lead to a variety of unsaturated products. The use of polyfluoroalkanes as fluorous-phase media for biphase separation techniques is briefly mentioned.
The chemistry of perfluoroalkenes is
rich and diverse; their reactions are
compiled in the form of tables and figures. Fluoride-ion-induced additions,
rearrangements, and oligomerizations
of perfluoroalkenes are also briefly covered. Electrophilic and free-radical
additions to polyfluoroalkenes are also
discussed, including the steric and electronic orientation of the attack. Some
aspects of the polymerization of perfluoroalkene monomers, and the role
of perfluoroalkenes in cycloaddition
reactions, are discussed. Short accounts
of the chemistry of fluoroalkynes, fluoroalkylalkynes, and fluoroallenes are
included.
Chapter 8 covers the rich chemistry
of fluoro-substituted oxygen, sulfur,
and nitrogen compounds. These include
carbonyl derivatives, alcohols, alkoxides, oxiranes, peroxides, sulfides, sulfonic acid derivatives, thiocarbonyls,
Angew. Chem. Int. Ed. 2005, 44, 2321 – 2323
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