Eclectic Transformers

Lewis Acids in Organic Synthesis.Vol. 1�2. Edited by Hisashi Yama-moto. Wiley-VCH, Weinheim2000. ixx � 995 pp., 750 figs., hard-cover DM 748.00 (ca. 382 E).ÐISBN 3-527-29579-8

The demands for efficient organicsynthesis are continously increasing. Re-actions are not only required to proceedin high yields andwith high selectivi-ty, they should alsobe carried out in aneconomically andecologically favor-able manner. A re-cent active area ofresearch meetingthese demands isthe utilization ofLewis acids in organic synthesis. In thistwo-volume work a team of internation-ally renowned authors has succeeded indemonstrating the usefulness of many me-tal complexes as Lewis acids in a plethoraof synthetically important reactions

The first volume deals with ªclassicalºLewis acidic compounds such as lithium,magnesium, boron, aluminum, silicon,and tin complexes. After a short discus-sion of the historical background, in-cluding for example the use of Friedel ±

Crafts catalysts, special emphasis is givento investigations leading to highly activeand selective species. Separate chaptersare devoted to the preparatively highlyimportant chiral aluminum and boronLewis acids, to emphasize the usefulnessof enantioselective transformations inmodern research. The frequently em-ployed Lewis acid catalyzed reactions ofallylic tin and indium reagents are alsotreated adequately.

The second volume deals with Lewisacids derived from transition metals.Today these compounds constitute anintegral part of modern organic synthe-sis. Although the main focus is on the useof achiral and chiral titanium Lewisacids, other reagents, including somemore ªexoticº examples such as anti-mony and hafnium complexes, are notneglected. As well as enantioselectivereactions, the volume also covers dia-stereoselective processes, which are atleast as important from a preparativestandpoint. A rather interesting chapterdiscusses transition metal complexesfrom vanadium to platinum. It is nicelypointed out that the electronic charac-teristics of the ligand, as well as of themetal itself, are important in influencingselectivity and reactivity.

In principle the subject of Lewis acidsin organic synthesis can be organizedeither according to the metals (as it ishere) or according to the types ofreactions. Although the chapters treatthe subject under the various types ofmetal complexes, the well sorted indexallows one to quickly find informationabout a given reaction, such as theDiels ± Alder reaction or the Mukaiya-ma aldol reaction.

The work is well worth buying for thewealth of information that it contains,

and for the extensive literature coverage.The clear discussion of modern conceptsleads the way for exciting novel develop-ments. It is fun to read this extensivecoverage of an exciting field.

Andreas GansäuerKekule -Institut für

Organische Chemie und BiochemieUniversität Bonn (Germany)

Contemporary Boron Chemistry.Edited by Matthew G. Davidson,Andrew K. Hughes, Todd B. Marderand Ken Wade. Royal Society ofChemistry, Cambridge 2000. xvi �538 pp., hardcover £ 92.50.ÐISBN0-85404-835-9

Contemporary Boron Chemistry is atypical ªproceedingsº volume, and con-tains the texts of papers discussed at the10th International Conference on BoronChemistry (IMEBORON X), held at theUniversity of Durham. (The previousvolume, reporting on IMEBORON IX,was published in 1997.) The presentvolume contains 80 contributions, whichvary in length from 3 to 8 pages and giveinterim reports on progress in the vari-ous research topics. In most cases thepublications cited are not confined to theauthors� earlier work, but also includeother key references, so that the readercan dig more deeply into the topicconcerned. As well as a detailed list ofcontents, there is an index of authors anda comprehensive subject index. Theindividual articles mainly follow a uni-form clear layout, although occasionally

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This section contains book reviews and a list ofnew books received by the editor. Book reviewsare written by invitation from the editor. Sug-gestions for books to be reviewed and for bookreviewers are welcome. Publishers should sendbrochures or (better) books to the RedaktionAngewandte Chemie, Postfach 10 1161, 69451Weinheim, Germany. The editor reserves theright of selecting which books will be reviewed.Uninvited books not chosen for reviews will notbe returned.

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the readability suffers from figures thatare too small, lines too closely spaced, orformula schemes cluttered with toomuch fine detail.

The editors have succeeded well inpresenting the very heterogeneous sub-ject matter in as clear a form as possible,grouping the contributions in nine chap-ters. There is a good balance betweenarticles on fundamental research topicsand those where the main emphasis is onapplications. Comparable amounts ofspace are devoted to electronicallywell-defined boron compounds and tocluster molecules.

Chapter 1 is concerned with the use ofboron compounds in catalytic olefinpolymerization, and provides a usefulsurvey of the latest developments in thishighly topical area. The aspects treatedrange from the design of boron-contain-ing ligands as a way of controlling theelectronic properties of the central met-al, through self-activating systems basedon Lewis acid boryl substituents, tonovel noncoordinating anions based oncarboranes or adducts of B(C6F5)3.

Chapter 2 is devoted to materials andpolymers. The topics covered includeoptimized precursors for producing BNor SiBCN ceramics, and arylene-carbor-ane polymers, which show great promiseas high temperature resistant plastics.Polymers in which boron centers formpart of a p-conjugated system offerinteresting possibilities for nonlinearoptics and the development of (blue)light-emitting diodes.

Chapter 3 describes the newest gen-eration of boron carriers for treatingtumors by neutron capture therapy.Some of the material here overlaps withthe following chapters, which deal withthe general chemistry of boron clusters,carboranes, metallaboranes, and metal-laheteroboranes. Even after many yearsof research, the chemistry and photo-chemistry of these classes of compoundscontinues to produce a wealth of unex-pected results, which are clearly andcomprehensively summarized in thisbook. One also learns about improvedmethods for preparing small clusters orlarge conjuncto-boranes.

Compounds containing M ± B 2e2cbonds (where M is a transition metal),which were scarcely known ten yearsago, have now been thoroughly cata-logued, and have already found applica-

tions in homogeneously catalyzed organ-ic transformations. These discoveries arecertainly a highlight of the chapter onthe organic and inorganic chemistry ofmono- and diborane systems. It alsobecomes evident that there are still someunsolved fundamental problems in themolecular chemistry of boron (for ex-ample, the problem of synthesizing aB� Si double bond), and these providemany ideas for future research projects.The last chapter of the book presentsexamples of the valuable informationyielded by theoretical methods, both formolecular boron compounds and inrelation to solid-state structures.

To summarize, Contemporary BoronChemistry is an indispensable referencesource for specialists in the field, and itwill also be a valuable guide for thesynthetic chemist with a taste for exper-imenting in areas away from the well-trodden paths. The book is not verysuitable for students. On the other hand,it will certainly be a valuable addition tolibraries.

Matthias WagnerInstitut für Anorganische Chemie

Universität Frankfurt am Main(Germany)

Flat Panel Displays. Advanced Or-ganic Materials. (Materials Mono-graphs. Series editor: J. A. Connor.)By Stephen M. Kelly. Royal Societyof Chemistry, Cambridge 2000.232 pp., hardcover £ 59.50.ÐISBN0-85404-567-8

In the late 1990s flat imaging screens,as space-saving display devices with alow energy consumption, became a veryimportant part of almost every area ofour daily life. The most familiar of theseare liquid crystal displays (of which morethan two billion units were producedworldwide in the year 2000), but recentlyvarious types of electroluminescent dis-plays have also played an increasing role.Many of the display systems now on themarket use technologies based on ad-vanced organic materials. In this book

S. M. Kelly presents the first concisesurvey explaining the principles of themost important types of flat panel dis-plays, and describing the relevant prop-erties of the organic materials used.

The first chapter briefly reviews themost important display technologies,and discusses the advantages and dis-advantages of the different types from anapplications viewpoint. All the followingchapters are devoted to the two organic-materials-based technologies that are ofgreatest commercial importance, namelyliquid crystal displays (LCDs) and elec-troluminescent devices based on organiclight-emitting diodes (OLEDs). Eachchapter includes an extensive bibliogra-phy, providing a solid basis for more in-depth reading.

First the author gives a short intro-duction to the physical properties ofthermotropic liquid crystals and thegeneral principles of LCDs. This isfollowed by a more thorough discussionof the technologies involved in thedifferent detailed aspects of LCDs, inan informative and carefully presentedaccount which emphasizes the logic oftheir historical development. Kelly de-votes special attention to structure ±properties relationships in the variousorganic materialsÐa highly topicaltheme, the theoretical aspects of whichare only just beginning to be understood.

For chemists especially, it would havebeen helpful to include here at least afew examples of reaction schemes forsynthesizing the most important classesof liquid crystals. It is also rather un-fortunate that the discussion of materialsfor active matrix liquid crystal displays(AM-LCDs), in which there has been anenormous upsurge of development ac-tivity in the last five years, does not giveenough information relating to real sys-tems. In particular, although Tables 3.11and 3.12 list various materials used ascomponents in liquid crystal mixtures forcommercial AM-LCDs, they do notinclude a single one of the fluorinatedphenylbicyclohexyl derivatives that havebeen by far the most common singleconstituents, in terms of quantity, inrecent years. On the other hand, it ispleasing to note that even some very newtechnologies, such as the IPS (in-planeswitching) mode of operation, are dis-cussed from both the materials and themechanistic viewpoints.

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The section on OLED technology,which was only in its infancy until quiterecently, is arranged in two parts. Thefirst begins with a concise explanation ofthe physical fundamentals of organiclight-emitting diodes, then goes on todescribe display systems using small-molecule organic materials. The secondpart deals with LEDs based on organicpolymers. In both parts the author de-votes particular attention to describingspecial types of display configurations,and discusses the different requirementsfor the materials to be used in suchsystems. The chapters include accountsof progress with different approaches tosolving the technical problems that havehindered the advance of OLED tech-nology from the R & D phase intocommercial production, and these makevery absorbing reading.

In discussing the outlook for organicmaterials in flat displays, Kelly returns toconsidering the products in which theyfinally reach the end-user: notebookcomputers, PCs, mobile telephones, tele-vision receivers, etc. Starting from theperspectives of the technology and thecommercial needs, he develops whatseems to be a very realistic forecast ofadvances in the next few years.

Although the book has some smallfaults (too many printing errors, some ofwhich are seriously misleading, and a notvery attractive page layout), the overallverdict is positive. The book is wellstructured from a learning standpoint,concentrates on the most importanttechnologies, and provides sound ex-planations of the physical principles ina clear way that will also be understoodby nonspecialists. It also conveys a feel-ing for the characteristics of research onmaterials for flat displays that make itespecially attractive: the interdisciplina-ry collaboration between chemistry,physics, and engineering, and the unusu-ally close connection between funda-mental research and technological ap-plications. Therefore the book can berecommended unreservedly for interest-ed chemists and physicists as a soundintroduction to this fascinating and veryactive field of research.

Peer KirschMerck KGaA, Liquid Crystals Division

Darmstadt (Germany)

High-Resolution NMR Techniquesin Organic Chemistry. By Timo-thy D. W. Claridge. Pergamon Press,Oxford 1999. vix � 382 pp., soft-cover $ 49.50.ÐISBN 0-08-042798-7

Modern NMR spectroscopy has hadan enormous analytical impact on struc-tural questions in nearly all fields ofchemistry, and that is still evolving. To-day�s combination of modern instrumen-tal equipment and established, as well asnewer, NMR methods puts a vast num-ber of important analytical experimentsat the chemist�s disposal. However, inorder to be able to use the wholeanalytical range of NMR spectroscopymost effectively, and to tailor it tospecific problems, there is a price topay. Anyone wishing to use it withreasonable efficiency needs to acquire asolid knowledge of the basic principles,as well as an overview of the mostimportant experimental techniques andtheir analytical meaning. That is exactlythe purpose of this book by T. D. W.Claridge, which aims to provide a firmbasis of fundamental knowledge as ap-plied to small and mid-sized molecules.In a nonmathematical approach, basedfirmly on using pictorial descriptions andnumerous instructive figures, the authorpresents a selection of more recentlydeveloped methods as well as alreadyestablished experiments, which are chos-en for their wide applicability. More thanten years after Andy Derome�s famousbook Modern NMR Techniques forChemistry Research, this book is pub-lished in the same series and can be seenas its modern successor.

After a short introduction in Chapter1, the theoretical basis for recordingNMR spectra is given in Chapter 2.The various theoretical aspects are de-scribed in conjunction with the relevantpulse sequences and illustrative exam-ples in a very informative way, thusshowing their direct connection. InChapter 3 all practical requirements torun an NMR experiment are describedin detail, together with their theoreticalbackground. The various acquisition andprocessing parameters are explained,and general aspects such as phase cy-cling, quadrature detection, digital filter-ing, and automatic gradient shimmingare discussed. Sample preparation, spec-trometer calibration, and performance

tests are described in thorough detail,even including the calibration of pulsedfield gradients.

Chapter 4 is dedicated to homo- andheteronuclear one-dimensional techni-ques. The advantages and drawbacks ofthe most important decoupling, editing,and polarization transfer methods aredescribed, and alternative techniquesare compared.

As an example of two-dimensionalspectroscopy, the theoretical and exper-imental basis of the COSY (correlationspectroscopy) experiment, as well as theinterpretation of the spectra thus ob-tained, is explained in detail in Chapter5. After introducing signal selectionusing pulsed field gradients, the authordiscusses different COSY approachesand common types of homonuclearspectra. The propagation of magnetiza-tion within a spin system during aTOCSY (total correlation spectroscopy)experiment is described in a very in-structive way with the help of numerousfigures and examples.

Chapter 6 presents two-dimensionalheteronuclear experiments, and com-pares the two classical pulse sequencesHSQC (heteronuclear single-quantumcorrelation) and HMQC (heteronuclearmultiple-quantum correlation). Togeth-er with their gradient-selected phase-sensitive versions, hybrid experimentswith multiplicity editing, additionalTOCSY or COSY transfer, and long-range correlation are also described.

After a short discussion of J-resolvedspectroscopy in Chapter 7, Chapter 8deals with the NOE (nuclear Overhaus-er effect) and its applications, describingit with many graphic examples. Thebehavior of multispin systems in bothsteady-state and transient NOE experi-ments is described, with many applica-tions. Experimental aspects are alsodiscussed.

Lastly, Chapter 9 provides an over-view of recent experimental develop-ments. Different types of pulses, pulsesequences, and new pulse shapes arediscussed. Other aspects include com-parisons of the different selective pulseshapes and the various water-signal sup-pression methods. Furthermore, theprinciples of measuring diffusion con-stants and experiments on heterogene-ous samples with magic angle spinningare touched on.

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This book offers a detailed overviewof the theoretical basis and the practicalaspects of NMR spectroscopy, and suc-cessfully presents a selection of the mostimportant and commonly used NMRexperiments as applied to small and mid-sized molecules. With only very fewmathematical formulas and in a pictoriallanguage, theory and practice are ex-plained using many well-selected exam-ples and numerous excellent and instruc-tive figures. Thus, for each experiment

the advantages and drawbacks, as well aspossible sources of artefacts, are dis-cussed, and much practical advice isgiven. For the budding NMR spectro-scopist, for the synthetic chemist with aninterest in and contact with NMR spec-troscopy, and also as a foundation forgraduate-level courses on NMR techni-ques, this book is highly recommended,providing a broad basis of backgroundknowledge. Additionally, with its de-tailed explanations of all practical as-

pects, but mainly without giving valuesof experimental parameters, this book isideal if used in combination with thebook 150 and More Basic NMR Experi-ments, by Braun, Berger, and Kalinow-ski. It is essential for every NMR labo-ratory dealing with small and mid-sizedmolecules.

Ruth GschwindFachbereich Chemie

Universität Marburg (Germany)