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Book Review Titanium and Zirconium in Organic Synthesis Edited by Milan Marek.

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Books
Titanium and Zirconium in
Organic Synthesis
Edited by Milan
Marek. Wiley-VCH,
Weinheim 2002.
512 pp., hardcover
E 159.00.—ISBN
3-527-30428-2
It is now 16 years since Reetz wrote the
first monograph reviewing this subject:
Organotitanium Reagents in Organic
Synthesis (Springer Verlag 1986). Since
then, there have been numerous other
books relating to the topic (among
others: Organometallics in Synthesis—
A Manual, Ed.: Schlosser, Wiley 1994;
Synthesis of Organometallic Compounds, Ed.: Komiya, Wiley 1998). In
view of the enormous increase in knowledge during those 16 years, it is time to
review the topic again and to show the
present capabilities of titanium and
zirconium for organic chemistry. In his
book Titanium and Zirconium in Organic Synthesis the editor Milan Marek
has now attempted that task.
The book begins with a detailed
introduction by Victor Snieckus. That
is followed in Chapter 1 by a very good,
clear, and comprehensive survey by Eiichi, Negishi, and Huo of the preparation of zirconocene derivatives and their
use in organic syntheses. They have
succeeded in bringing order and clarity
to the sometimes very confused literature on this topic, and they describe
some fascinating examples of applications in natural products syntheses. In
Chapter 2 Takahashi and Li describe the
syntheses of zirconacyclopentadienes
852
and their applications in organic chemistry, and this is followed in Chapter 3
(Dixon and Whitby) by a review of
reactions in which a-halogen-a-lithium
species (carbenoids) are inserted into
zirconium – carbon bonds. In Chapter 4
Lipshutz and co-authors describe the
hydrozirconylation of alkenes and alkynes, which is one of the most important applications of zirconocene chloride (the Schwartz reagent which has
been known for nearly 30 years). They
illustrate the usefulness and versatility
of this method by describing some impressive applications in natural products
syntheses. In Chapter 5 Hanzawa reviews the preparation and uses of acylzirconocenes. Chapter 6 (Hoveyda) describes the use of zirconium catalysts for
enantioselective formation of C – C and
C – N bonds. This chapter is a mine of
information for every chemist who has
to solve problems in the area of stereoselective synthesis (enantioselective introduction of magnesium, intramolecular alkylations, alkylation of alkenes,
allylation of aldehydes, alkylation of
imines, addition of cyanides to aldehydes and meso-epoxides, the Strecker
reaction, aldol additions, the Mannich
reaction, cycloadditions). In Chapter 7
Dembitsky and Srebnik describe the
preparation and applications of gemmetallozirconocenes. Here, unfortunately, there is considerable duplication
of material in Chapter 4 by Lipshutz
(e.g., Scheme 7.17 duplicates information in Schemes 4.43 and 4.44 of Chapter
4; also in Scheme 7.17 “cyclopentanone”
should be cyclopentenone). Chapter 8,
by Suzuki and co-authors, reviews the
use of cationic zirconium species in
organic synthesis. These are formed as
intermediates by the interaction of zirconocenes with silver perchlorate. The
authors describe nice examples of applications to the synthesis of glycosides and
oligoglycosides. Other applications of
these reagents are in nucleophilic reactions with epoxides, in carbometalation
of alkynes and alkenes, in allylzirconylation and alkylzirconylation reactions,
and as Lewis acids in Diels – Alder and
Mukaiyama reactions. In Chapter 9 Sato
and Urabe review the preparation of
dialkoxytitanium species and their uses
in organic synthesis. The formation of
low-valent titanium species from alkyl
derivatives of titanium by b-hydride
) 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
0044-8249/03/4208-0852 $ 20.00+.50/0
elimination followed by further rearrangement has led to a number of very
important reactions, such as intramolecular nucleophilic acyl substitution (the
INAS or Kulinkovich reaction). However, the treatment of these titanium
complexes in this chapter under the
heading “Titanium(ii)Alkoxides” alkoxides is probably not quite correct and
even misleading. The reaction is discussed again in a lucid and understandable way in Chapter 11 by De Meijere
and co-authors. They describe the synthesis of cyclopropanols and cyclopropylamines by the reaction of low-valent
titanium species with carboxylic acid
esters and amides respectively, clearly
explained with equations and tables. For
organic synthetic chemists, it is a pleasure to read this excellent chapter. It is
unfortunate that some overlapping has
resulted from the premature treatment
of this reaction in Chapter 9 (e.g.,
between Equation 9.36 and Table 11.7
and between Equation 9.41 and Scheme
11.11). Chapter 10, by Rosenthal and
co-authors, again deals with an important area of organometallic chemistry,
titanocene and zirconocene complexes
of bistrimethylsilylacetylene, and presents a review of the groupAs research on
the topic. The authors could have made
it easier for readers by including more
equations, as only a small proportion of
the schemes (about 30 %) take the form
of equations, while the rest appear as
lists summarizing the compounds prepared. Consequently one has to work
out from the text which transformations
were carried out. In Chapter 12 GansDuer and Rinker review both racemic and
enantioselective epoxide ring-opening
reactions catalyzed by titanocenes. The
studies reported by Szymoniak and
Moise in Chapter 13 appear to be
developing into a useful extension of
existing allylboron chemistry. These authors summarize the synthesis and reaction properties of allytitanium derivatives. The examples of allylation of
aldehydes are especially impressive. The
transformations in which an allylation is
combined with a Mukaiyama reaction
open up possibilities for building up
stereopentads and stereosextads of defined stereochemistry in a single synthetic step. The book ends with a review
by Takeda of the use of titanium compounds in metathesis reactions. This
Angew. Chem. Int. Ed. 2003, 42, No. 8
Angewandte
Chemie
relates to both the classical Tebbe reaction and the Peterson olefination of
carbonyl compounds. The author discusses the formation of titanacyclobutenes by the addition of a Tebbe reagent
to a triple bond, followed by further
reactions involving carbonyl compounds
and nitriles.
It is pleasing to note that each
chapter ends with a description of general experimental methods. This allows
even newcomers to the field to get a feel
for the potential uses of the transformations described in the book. Organic
synthetic chemists will certainly regret
that Chapter 6 by Hoveyda on chiral
zirconium catalysts does not have a
counterpart dealing with titanium catalysts. Such a chapter would include
various important topics: the McMurry
reaction, allylations, aldol additions, alkylations, cycloadditions, dihydroxylations, epoxidations, oxidations, hydroaminations of alkynes, etc.
Some chapters of the book would
make easier reading if the compounds
were identified by a sequential numbering system. In five of the fourteen
chapters the compounds are not numbered at all, and in Chapter 8 the same
letters are used for different compounds
(see Schemes 8.21, 8.23, and 8.25).
Rainer Mahrwald
Institut f5r Chemie
Humboldt-Universit7t
Berlin (Germany)
Angew. Chem. Int. Ed. 2003, 42, 852 – 853
Peptides: Chemistry and Biology
By Norbert Sewald
and Hans-Dieter
Jakubke. WileyVCH, Weinheim
2002. xxxiv þ 563
pp., hardcover,
E 98.00.—ISBN
3-527-30405-3
Sewald and Jakubke have produced a
remarkable volume on the chemistry
and biology of peptides, which will be a
valuable addition to the library of peptide chemists who want to keep abreast
of this rapidly growing area. It is a well
balanced book, beginning with a brief
introduction to amino acids and peptides and a review of methods for their
isolation, purification, and analysis, followed by more extended discussions of
the physical and chemical techniques for
characterizing the products. The book
then moves on to a more advanced and
detailed discussion of the strategy and
tactics of peptide synthesis. This begins
with the classical strategy of synthesis in
homogeneous solution, dealing with
protecting groups for a-amino, a-carboxyl, and side-chain functions. However, this is not a simple cataloging of
these groups but a careful attempt to
evaluate and compare the many tactics
available. The critically important matter of selecting activating and coupling
reagents is covered in detail, and their
relative advantages and disadvantages
are weighed, with particular emphasis
on kinetics, racemization, and other side
reactions. In many cases the mechanisms
of the reactions are presented.
Adequate space is also devoted to
solid-phase peptide synthesis, the other
) 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
broad strategy of peptide synthesis. All
the important parameters of this approach are covered, and each of the
many variations is carefully and justly
evaluated. Other ways to produce peptides and proteins are not ignored,
including enzyme-catalyzed synthesis,
genetic engineering, and the most recent
techniques of combinatorial library synthesis and ligation methods. These are
all very important advances which are
continuing to revolutionize the field.
There is an early chapter on biological peptides, and another on special
peptides including glyco-, phospho-, and
lipopeptides, and also cyclic peptides
and peptide mimetics. These chapters
are supplemented by a 114-page glossary of biologically active peptides.
This is a most carefully written and
edited volume, and no significant errors
in the English or the factual material
could be found. All of this large amount
of information is documented by some
1500 references to the relevant publications selected from a much larger literature. Inevitably some of the important
references are not included, but in
general the best ones were chosen. A
detailed table of contents, a list of
abbreviations, and a subject index are
included and are very helpful, especially
when the book is used as a reference
volume. Although a complete alphabetical author index would also have been
valuable, it probably would have added
too much to the present 563 pages.
It comes through clearly that this
monograph is written by experts who
are experienced in the peptide field and
it will be widely accepted.
Bruce Merrifield
Department of Biochemistry
The Rockefeller University
New York (USA)
0044-8249/03/4208-0853 $ 20.00+.50/0
853
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