Angewandte Chemie International Edition in English

Cover image for Vol. 34 Issue 3

February 21, 1995

Volume 34, Issue 3

Pages 251–363

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 3/1995)

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199502491

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      The cover picture shows an intramolecular electron-transfer reaction through duplex DNA. The DNA has been covalently and site-specifically labeled with two different redox-active ruthenium complexes to produce a donor –DNA–acceptor system. After laser excitation, the kinetics of intramolecular electron transfer from RuII to RuIII center through DNA was measured by transient-absorption techniques. This system is designed to delineate the roles of base sequence and π stacking in modulating the rates of long-range electron-transfer reactions. More about this elegant method for providing well-defined model systems to probe the important and topical issue of electron-transfer through DNA is reported by T. J. Meade and J. F. Kayyem on p. 352 ff.

  1. Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Atom Economy—A Challenge for Organic Synthesis: Homogeneous Catalysis Leads the Way (pages 259–281)

      Prof. Barry M. Trost

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199502591

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      If all atoms of the starting materials are found in the product and only catalytic amounts of other reagents are needed, a reaction may be defined as ideal. A promising route to this ideal state is approached by the use of transition metal complexes as catalysts for addition and isomerization reactions. In this way, for instance, seven rings have been formed very efficiently from an acyclic precursor in a single step according to Equation (a).

    2. Digitalis Research in Berlin–Buch—Retrospective and Perspective Views (pages 282–294)

      Prof. Dr. Kurt R. H. Repke, Dr. Rudolf Megges, Dr. Jürgen Weiland and Dr. Rudolf Schön

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199502821

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      The analysis of the relation between configuration and action of steroids at the receptor level has led to the discovery that–contrary to the ruling dogma–C/D-trans steroids 1 of hormone type can improve cardiac contractility like the therapeutically applied C/D-cis steroids 2 of digitalis type, and that the former may thus be used as lead structures for the design of novel cardioactive drugs.

  2. Highlights

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Five-Membered Aromatic and Antiaromatic Rings with Gallium, Germanium, and Bismuth Centers: A Short March through the Periodic Table (pages 295–298)

      Prof. Dr. Hansjörg Grützmacher

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199502951

      Criteria for aromaticity–a topic with staying power! Planarity of the rings, bonds of equal length, stabilization energies, and the number of π electrons were considered among the characteristics of the important phenomenon of aromaticity, but no one of these features is generally valid. Schleyer et al. (p. 334 in this issue) have now correlated the criteria with ab initio IGLO calculations on five-membered heterocycles. In addition this highlight collates the synthesis methods and the chemical properties of these interesting compounds.

    2. Oxidative Polycyclization versus the “Polyepoxide Cascade”: New Pathways in Polyether (Bio)synthesis? (pages 298–300)

      Dr. Ulrich Koert

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199502981

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      By which route is monensin A biosynthesized? Is an (E.E.E.) triene first epoxidized and the polyepoxide then transformed into the natural product in a cascade of ring openings and ring closures? Or does a (Z.Z.Z.) triene undergo successive oxidative cyclizations to give monensin A directly? New results from McDonald and Towne, who carried out oxidations of (Z) dienes with pyridinium chlorochromate, support the second route.

  3. Communications

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Efficient Heterogeneous Biocatalysts by Entrapment of Lipases in Hydrophobic Sol–Gel Materials (pages 301–303)

      Prof. Dr. Manfred T. Reetz, Dipl.-Biochem. Albin Zonta and Dr. Jörg Simpelkamp

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503011

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      Alkyltrimethoxysilanes yield much better host matrices for lipases than tetramethoxysilane (see picture). This is revealed by the esterifications discussed herein catalyzed by lipases that are immobilized in RSi(OMe)3 gels. These heterogeneous biocatalysts are readily reusable and should also be suitable for continuous processes.

    2. Oligothiophenes—Yet Longer? Synthesis, Characterization, and Scanning Tunneling Microscopy Images of Homologous, Isomerically Pure Oligo(alkylthiophene)s (pages 303–307)

      Prof. Dr. Peter Bäuerle, Dipl.-Chem. Thomas Fischer, Bernd Bidlingmeier, Prof. Dr. Jürgen P. Rabe and Dipl.-Chem. Andreas Stabel

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503031

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      Sixteen thiophene units make up the longest oligothiophene to date, the 64 Å-long oligomer 4. Like its shorter homologues 1–3, 4 forms molecular structures on surfaces, which can be examined by scanning tunneling microscopy with submolecular resolution. Oligomers 1-4 can be considered components of “molecular wires” and serve as model compounds for the study of charge transport in electrically conducting polymers.

    3. New Selenolato-Bridged Clusters of Iron and Nickel; the Structures of [Fe12(SePh)24] and [Na2(POPh3)6][Ni20Se12(SeMe)10] (pages 307–309)

      Prof. Dr. Dieter Fenske and Dipl.-Chem. Andreas Fischer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503071

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      A twelve-membered ring made up of Fe2+ ions is present in the cluster framework of 1 (shown on the right without phenyl groups; Fe atoms are white, Se atoms shaded). The Fe2+ ions are located in the centers of edge-sharing Se4 tetrahedra, which in turn form a ring. The shiny black needles of 1 are prepared from FeCl3, PPh3, and PhSeSiMe3, and decompose readily upon heating.

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    4. Side-Chain Polyrotaxanes with a Tandem Structure Based on Cyclodextrins and a Polymethacrylate Main Chain (pages 309–311)

      Markus Born and Prof. Dr. Helmut Ritter

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503091

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      A new structural type for polyrotaxanes (shown schematically on the right) results from the condensation of an amino-substituted cyclodextrin semirotaxane with the free acid groups of a dicarboxylic acid group in the side chain of a polymethacrylate. The structure of the novel polyrotaxane was determined unequivocally by NMR spectroscopic studies and by comparisons with a cyclodextrin-free model compound.

    5. Structures of UV-B Induced Sunscreen Pigments of the Scots Pine (Pinus sylvestris L.) (pages 312–314)

      Dipl.-Chem. Tim P. Jungblut, Dr. Jörg-P. Schnitzler, Dr. Werner Heller, Prof. Dr. Heinrich Sandermann Jr., Dr. Norbert Hertkorn, Dr. Wilfried Szymczak and Dr. Jörg W. Metzger

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503121

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      Diacylated flavonol glycosides are the response of Scots pine seedlings to UV-B irradiation. The two induced compounds 1 and 2 both have their absorption maximum at 315 nm (ϵ = 50300) in the range of UV-B radiation (290–320 nm), are compartmented in the epidermis, and offer much better protection than the monoacylated analogues at the same molarity.

    6. Self-Assembled Helicates of Zinc and Cadmium Cyanides, [Mx(CN)2x+1], x ≤ 27 (pages 314–316)

      Prof. Ian Dance, Prof. Phillip Dean and Dr. Keith Fisher

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503141

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      Laser ablation of Zn(CN)2 and Cd(CN)2 gives rise to a series of anions [Mx(CN)2x+1], which have helical structures according to density functional and force-field calculations. M atoms with trigonal-planar coordination and each bearing a terminal CN ligand are linked by linear M[BOND]CN[BOND]M bridges to form helices. The supramolecular helices are stabilized by interstrand coulombic interactions. The calculated structure of [Zn27(CN)55] is shown on the right equation image = Zn, equation image = C, equation image = (N)

    7. Novel Alkali Metal Phosphanide Aggregates (pages 316–318)

      Priv.-Doz. Dr. Matthias Driess, Prof. Dr. Gottfried Huttner, Dipl.-Chem. Norbert Knopf, Dr. Hans Pritzkow and Dr. Laszlo Zsolnai

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503161

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      Clusters from lithium or sodium, phosphorus, and silicon form the frameworks of the title compounds 1–4. Compound 2 consists of two clusters 1, which are “glued together” by a (LiCI)2 ring. Compounds 3 and 4 form under the same conditions; 4 relieves the ring strain by opening the polyhedron. Two Na centers in 4 are each η2-coordinated to one toluene (L) molecule. SiR2 = SitBuIs, Is = 2,4,6-iPr3C6H2; PR = PSiiPr3.

    8. Reactions of 1,1′-Ferrocenediylbis{chloro-[(1,2,5,6-η)-1,5-cyclooctadiene]}diplatinum with Triarylphosphane and Molecular Oxygen (pages 319–321)

      Toshiya Yoshida, Shigeaki Tanaka, Dr. Kiyotaka Onitsuka, Prof. Dr. Kenkichi Sonogashira, Tomohiro Adachi and Prof. Dr. Toshikatsu Yoshida

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503191

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      The paramagnetic hydroxo-bridged diplatinum complex 1 (X = CI) results from the reaction of the title compound with O2 and triphenylphosphane. The ferrocene unit in 1 not only fixes the two Pt atoms at an appropriate distance but also functions as an electron pool, as reactions with CO and pyridine show.

    9. Complexes from Polyazacyclophanes, Fluorescence Indicators, and Metal Cations—An Example of Allosterism through Ring Contraction (pages 321–323)

      Dipl.-Chem. Ralf Baldes and Prof. Dr. Hans-Jörg Schneider

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503211

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      A cavity can be made to fit an aromatic guest molecule in certain polyazacyclophanes by contraction of the inner volume, which is initiated by the binding of metal cations. The anticipated cooperative effects can be quantified by fluorescene spectroscopy with suitable indicators, which opens new possibilities for the detection of, for instance, zinc ions in aqueous solution. The ternary complex formed from ligand, metal ion M, and guest G is depicted on the right.

    10. Preparation and Detection of Enantiomerically Enriched and Configurationally Stable α-Thioalkyllithium Compounds (pages 323–325)

      Bernd Kaiser and Prof. Dr. Dieter Hoppe

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503231

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      Sterically demanding and carbanion-stabilizing substituents like SiMe3 raise the barrier to the configurational inversion of α-thioalkyllithium compounds. With such substituents these compounds can undergo, for example, electrophilic substitution [Eq. (a)] without changes in configuation. Experiments with deuterated compounds proved that alkyllithium intermediates from primary S-alkylthiocarbamates are typically not configurationally stable.

    11. [Fe(2,4,6-tBu3C6H2)2], a Monomeric Diaryl Complex with Two-Coordinate Iron(II) (pages 325–327)

      Prof. Dr. Wolfgang Seidel, Dr. Hardy Müller and Dr. Helmar Görls

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503251

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      The surprising thermal stability of the first monomeric, homoleptic diaryliron(II) complex 1 arises because its Fe center is very well shielded by the sterically demanding ligands. The magnetic moment of 4.77 μB indicates a high-spin state of the highly soluble, air- and moisture-sensitive complex.

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    12. Compounds with Planar Tetracoordinate Boron Atoms: Anti van't Hoff/Le Bel Geometries without Metal Centers (pages 327–329)

      Dipl.-Chem. Matthias Menzel, Dirk Steiner, Heinz-Jürgen Winkler, Dieter Schweikart, Dr. Sigrid Mehle, Dipl.-Chem. Stefan Fau, Prof. Dr. Gernot Frenking, Prof. Dr. Werner Massa and Prof. Dr. Armin Berndt

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503271

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      Electropositive elements are prerequisites for the formation of anti van't Hoff/Le Bel geometries, as evident in compounds 1, which contain planar tetracoordinate boron atoms in the CB2H framework. These compounds extend the range of molecules of this structural type to include those without metal atoms. R = CH(SiMe3)2, R′ = 2,3,5,6-Me4C6H.

    13. 1,3,5,7-Tetra-tert-butyl-4-aza- and 1,3,5,7-Tetra-tert-butyl-4-phospha-s-indacene (pages 330–332)

      Dipl.-Ing. Stefan Schardt, Prof. Dr. Klaus Hafner, Dr. Teodor Silviu Balaban and Dr. Volker Sturm

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503301

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      s-Indacenes reveal the limits of the Hückel rules: These 12π systems are formally antiaromatic, but the results of more recent quantum mechanical calculations indicate π-electron delocalization. The synthesis and spectroscopic investigation of the non-electronically stabilized 4-hetero-s-indacenes 1 and 2 have now been achieved for the first time.

    14. Surprising Formation of a Carborane-Substituted Digallane (pages 332–334)

      Dr. Anil K. Saxena, Dr. Hongming Zhang, Prof. Dr. John A. Maguire, Prof. Dr. Narayan S. Hosmane and Prof. Dr. Alan H. Cowley

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503321

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      A very short Ga[BOND]Ga bond, stabilized by carborane moieties, is present in the digallane 1, which is air- and moisture-sensitive, and soluble in both polar and nonpolar organic solvents. The coordination of each Ga atom to the respective C2B3 carborane face is “slip distorted”. • = H, □ = SiMe3.

    15. The Cope Rearrangement Transition Structure Is Not Diradicaloid, but Is It Aromatic? (pages 334–337)

      Dipl.-Chem. Haijun Jiao and Prof. Dr. Paul von Ragué Schleyer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503341

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      IGLO computations reveal the aromatic character of the transition structures 1 a and 1 b for the Cope rearrangement of 1,5-hexadiene. In addition, high-level ab initio calculations favor a synchronous concerted mechanism via intermediates not having sigificant diradicaloid character.

    16. Aromaticity and Antiaromaticity in Five-Membered C4H4X Ring Systems: “Classical” and “Magnetic” Concepts May Not Be “Orthogonal” (pages 337–340)

      Prof. Dr. Paul von Ragué Schleyer, Dipl.-Chem. Haijun Jiao, Dipl.-Chem. Bernd Goldfuss and Prof. Peter K. Freeman

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503371

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      Energetic, geometric, and magnetic criteria yield quantitatively the same order of aromaticity (antiaromaticity) for the five-membered ring systems 1: the aromatic 6π electron systems are stabilized, their bond lengths are equalized, and the magnetic susceptibility exaltations are diamagnetic. In contrast, the antiaromatic 4π electron systems are destabilized, double bonds are localized, and susceptibility exaltations are paramagnetic.

    17. Topochemical Aspects of the Formation of Networks in Layered Langmuir–Blodgett (LB) Assemblies (pages 340–343)

      Dipl.-Chem. Michael Seufert, Dr. Matthias Schaub, Prof. Dr. Gerhard Wegner and Prof. Dr. Gerhard Wenz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503401

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      The potential of rigid macromolecules as building blocks of supramolecular architectures is shown here by the reactions in LB layers from cellulose derivatives. With an appropriate sequence of layers, a two-dimensional network is accessible by Diels-Alder reaction between the side chains in the zones of overlap shown schematically on the right.

    18. Characterization of an Oxo(porphyrinato)manganese(IV) Complex by X-ray Absorption Spectroscopy (pages 343–346)

      Dr. John M. Charnock, Prof. Dr. C. David Garner, Prof. Dr. Alfred X. Trautwein, Dr. Eckard Bill, Dr. Heiner Winkler, Khadija Ayougou, Dr. Dominique Mandon and Prof. Dr. Raymond Weiss

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503431

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      The MnIV[DOUBLE BOND]O unit in the five-coordinate oxo(porphyrinato)manganese(IV) complex 2, which is formed by oxidation of the bromo(porphyrinato)manganese(III) complex 1 with potassium peroxycarbonate, was characterized by X-ray absorption spectroscopy. The relatively long Mn[DOUBLE BOND]O bond (1.69±0.03 Å) is probably attributable to the high-spin state and the low polarizability of the half-filled tmath image subshell of high-spin MnIV.

    19. Models for Bimetallic Catalysts: Multiple Oxidation States in Pt3Re Cluster Cations (pages 346–348)

      Leijun Hao, Dr. Jianliang Xiao, Dr. Jagadese J. Vittal and Prof. Richard J. Puddephatt

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503461

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      Twelve electrons more than the starting material, but the same cluster framework—this modification was achieved for the first time in the synthesis of the Pt3Re clusters 1 (66e) from [Pt3{Re(CO)3}(μ-dppm)3]+ (54e) and H2O2 or propene sulfide. The metal-oxygen units in 1 could serve as models for the interactions between oxo ligands and metal clusters, which are important in oxide-supported Pt[BOND]Re bimetallic catalysts.

    20. A Highly Stereoselective Optical Switching Process Based on Donor–Acceptor Substituted Dissymmetric Alkenes (pages 348–350)

      Dr. Wolter F. Jager, Dr. Johannes C. de Jong, Dr. Ben de Lange, Drs. Nina P. M. Huck, Drs. Auke Meetsma and Prof. Dr. Ben L. Feringa

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503481

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      The reversible photoisomerization of the helical thioxanthenes 1 and 2 leads to photostationary states with large diastereomeric excesses. These compounds are promising starting materials for optical data storage devices.

    21. Asymmetric Syntheses of Stavudine (d4T) and Cordycepin by Cycloisomerization of Alkynyl Alcohols to Endocyclic Enol Ethers (pages 350–352)

      Prof. Frank E. McDonald and Mark M. Gleason

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503501

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      Anti-AIDS deoxynucleosides like stavudine (d4T, 3) are now accessible in a short (five steps!) asymmetric synthesis. The “missing link” between the acyclic precursors and the product is a Mo(CO)5-catalyzed cycloisomerization. It yields the ether 2, the saccharide building block for many nucleosides, from 1 in 80% yield. R = tBuCO.

    22. Electron Transfer through DNA: Site-Specific Modification of Duplex DNA with Ruthenium Donors and Acceptors (pages 352–354)

      Dr. Thomas J. Meade and Dr. Jon F. Kayyem

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503521

      The rate of the electron transfer between two ruthenium centers at the ends of an octanucleotide duplex (metal-to-metal distance = 21 Å) was determined to be 1.6(4) × 106 s−1. By using automated DNA synthesis techniques, modified oligonucleotides were prepared with a protected phosphoroamidite of 2′-amino-2′-deoxyuridine. The NH2-modified oligonucleotides were hybridized with complementary DNA sequences to protect nucleotide bases, and then treated with ruthenium complexes. In this way the ruthenium complex was bound only to the free NH2 group.

    23. Structure and Bonding of Transition Metal Dihydrogen Complexes [M(CO)5(H2)] (M = Cr, Mo, W) (pages 354–357)

      Dipl.-Chem. Stefan Dapprich and Prof. Dr. Gernot Frenking

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503541

      Important intermediates in catalytic hydrogenation, η2-dihydrogen complexes are also appealing subjects for theoretical studies. The M[BOND]H2 binding enthalpies for the complexes [M(CO)5(H2)] (M = Cr, Mo, W) were calculated at the CCSD(T)/MP2 level as 15.9 (M = Cr), 12.8 (M = Mo), and 16.3 kcal mol−1 (M = W). Charge decomposition analysis suggests that H2 is a significant σ donor and a moderate π acceptor. The topological analysis of the electron density distribution indicates a cyclic structure for the MH2 moiety.

  4. Book Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Book Review: Shikimic Acid. By E. Haslam (page 361)

      Jürgen Rohr

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503611