Angewandte Chemie International Edition in English

Cover image for Vol. 31 Issue 8

August 1992

Volume 31, Issue 8

Pages 931–1100

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 8/1992)

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199209311

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      The cover picture depicts in the colors of Princeton University two interpenetrating tetrahedra which are nonsuperposable mirror images of each other. According to one of the measures of chirality discussed by Mislow et al. On p. 989 ff., these tetrahedra have attained the highest possible degree of asymmetric. Classical asymmetric shapes in organic chemistry result from the tetrahedral arrangement of four different atoms around a central carbon atom, as illustrated by the ball-and-stick models of the enantiomers above the tetrahedra. The review by by Mislow et al. Offers a critical discussion of the measures of chirality as well as an up-to-date report on this field—and thus certainly provides food for thought, discussion, and Correspondence.

    2. Graphical Abstract (Angew. Chem. Int. Ed. Engl. 8/1992)

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199209312

  1. Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Preparation and Properties, Reactions, and Applications of Radialenes (pages 931–954)

      Prof. Dr. Henning Hopf and Prof. Dr. Gerhard Maas

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199209313

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      The unusual molecular structures and π-electron systems of radialenes are as much a challenge for preparative chemists as for theoreticians. Two proven methods of synthesis that afford this class of compounds with parent compounds 1–4 are olefin-forming reactions at an existing cycloalkane skeleton and the thermal and metal-induced cyclooligomerization of [n]cumulenes. Most recently materials scientists have discovered these compounds in their search for organic conductors and ferromagnets.

    2. Nitrido Complexes of Transition Metals (pages 955–978)

      Prof. Dr. Kurt Dehnicke and Prof. Dr. Joachim Strähle

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199209551

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      New syntheses and numerous structure determinations have stimulated activity in the relatively new field of nitrido complexes. The nitrido ligand can be found in many different types of coordination, as exemplified by the T-shaped bridging function (N l) in the structure right. Practical applications of these complexes have already been realized: complexes with terminal nitrido groups are used in radiotherapy, and nitrido molybdenum complexes are suitable catalysts for olefin metathesis.

    3. In Vitro Selection of Specific Ligand-binding Nucleic Acids (pages 979–988)

      Dr. Michael Famulok and Prof. Jack W. Szostak

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199209791

      The more variety in the products of a synthesis the better! Although this strategy seems crazy to most chemists, it has recently become the guiding principle for a group of chemists and molecular biologists. From a very large number of different nucleic acid molecules (DNA and RNA), they increase the concentration of those that have particular properties, for example, the ability to bind specifically certain proteins, other oligonucleotides, or other “small” molecules. This is done on the assumption that some molecules in the original pool must have the right receptor structure; these are selected, for example by affinity chromatography, then amplified by the polymerase chain reaction. Even if the terminology disguises the fact, the field here is Organic Chemistry!

    4. On Quantifying Chirality (pages 989–1007)

      Dr. Andrzej B. Buda, Dr. Thomas Auf der Heyde and Prof. Kurt Mislow

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199209891

      “More” or “less” chiral—what does that mean? Are quantitative statements on chirality possible at all? Using triangles and tetrahedrons, that is figures in two-and three-dimensional space, the authors present the methods they developed for quantifying chirality and compare them with attempts by other research groups. The measures of chirality can be divided into two classes: one compares the object under consideration with an achiral reference object, while the other compares it with its enantiomorph. The second class was shown to be more widely applicable, and in particular, the Hausdorff measure, which is based on the distances between identical points of the enantiomorphs of an object when they are superimposed so that overlap is optimal, was selected by the authors as the best chirality measure to date. However, form analysis of rigid, abstract objects is still far removed from analysis of flexible molecules, and there is a long way to go before the degree of chirality can be measured by physical or chemical properties.

  2. Highlights

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Peptide Nucleic Acids(PNAs)—Unusual Properties of Nonionic Oligonucleotide Analogues (pages 1008–1010)

      Dr. Chris Meier and Prof. Dr. Joachim W. Engels

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210081

      The phosphate–sugar backbone of oligonucleotides was replaced with peptides in recent work by P. E. Nielsen et al. Specially designed by molecular modeling, these oligonucleotides offer several advantages over chemically modified natural oligonucleotides: they are available on a large scale by the Merrifield synthesis, relatively inert to nucleases because of the nonionic peptide section, and have very good hybridization properties as PNA–DNA binding studies testify. These new DNA mimics are thus exceptionally interesting subjects for study since they may be employed as antisense agents.

    2. Synthetic Models for Iron–Oxygen Aggregation and Biomineralization (pages 1010–1012)

      Prof. Karl S. Hagen

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210101

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      A description of the formation and structure of naturally occurring hydroxo(oxo)polyiron compounds is important in understanding the chemistry of iron in the biosphere and in the earth's crust. To this end a series of model compounds has been synthesized; the preparation of Fe[BOND]O clusters with 17 and 19 iron atoms by Powell et al. is the latest advance. The cluster cores represent the beginning stages of the biomineralization of iron oxides. The structure of the Fe19 aggregate 1 [• = Fe, • = O, ◯ = N (amine ligand)] is depicted here.

    3. Artificial Replication Systems (pages 1013–1016)

      Professor Dr. Siegfried Hoffmann

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210131

      Replicative information systems were the signal for the departure of Evolution into its biological phase and the leitmotiv for our scientific attempts at its imitation. This research diverted the paths of chemistry into complexity. The latest journeys along these routes taken by the research groups of von Kiedrowski, Orgel, and Rebek cover a wide area and are reported against the panorama of the historical development.

  3. Communications

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Molecular Recognition of Primary Amines by Three-Point Binding with Boron-Containing Host Molecules (pages 1017–1019)

      Prof. Dr. Manfred T. Reetz, Dipl.-Chem. Christof M. Niemeyer, Marcus Hermes and Dr. Richard Goddard

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210171

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      The reversible formation of a dative bond between the boron center (M) of the host and the N atom of the primary amine, with simultaneous formation of hydrogen bonds between the amine H atoms and two oxygen atoms (D) of the crown ether host presents a new concept in molecular recognition (depicted schematically right). The control of the degree and direction of the molecular recognition by variation of the groups R on the amine is unprecedented.

    2. Effect of Torsional Strain and Electrostatic Interactions on the Stereochemistry of Nucleophilic Additions to Cyclohexanone and Related Systems (pages 1019–1021)

      Prof. Dr. Yun-Dong Wu, Prof. Dr. Kendall N. Houk and Prof. Dr. Michael N. Paddon-Row

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210191

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      The equatorial attack of a nucleophile on the cyclic ketones 1–3 was compared at the ab initio level with the axial attack. The more stable transition structure was provided by the equatorial attack of LiH in the case of 2 and 3E = 1.5 and 7.9 kcalmol−1, respectively) but the axial attack in 1E = 1.4 kcalmol−1). This change in the stereoselectivity can be explained by the different torsional strains and electrostatic interactions. The fact that in experiments the axial attack is preferred for 2 is rationalized by the solvent effects which were not considered in the calculations.

    3. The Reaction of [Cpmath imageNb2(B2H6)2] (Cp+ = η/-EtMe4C5) with Sulfur: Stabilization of the Tetrathioborato Ligand in Novel Sulfido Niobium Clusters (pages 1021–1023)

      Prof. Dr. Henri Brunner, Günther Gehart, Dr. Joachim Wachter, Dr. Bernd Nuber and Prof. Dr. Manfred L. Ziegler (deceased)

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210211

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      An equilateral Nb3 triangle the edges of which are spanned by a BS4 tetrahedron and bridged by sulfido ligands on the “underside” is found in cluster 1. The synthesis of this cluster with an unusual electron configuration shows that tetrathioborates can serve as ligands in organometallic chemistry. Cmath image = η5-EtMe4C5.

    4. Palladium-Catalyzed C[BOND]H Activation of Methoxy Groups: A Facile Synthesis of Substituted 6H-Dibenzo[b,d]pyrans (pages 1023–1025)

      Dr. Gerald Dyker

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210231

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      A threefold domino coupling reaction of ortho-iodoanisole (1) affords dibenzopyran 2 in high yield (90%). This C-H activation at a methoxy group is a new reaction principle in palladium-catalyzed reactions.

    5. Carbene Osmium Complexes by Double Metalation of Alkoxylalkyl- and Aminoalkylphosphanes (pages 1025–1027)

      Prof. Dr. Helmut Werner, Dipl.-Chem. Birgit Weber, Dipl.-Chem. Oliver Nürnberg and Dr. Justin Wolf

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210251

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      The transformation of a methoxy or methylamino group into a carbene ligand is possible if it is part of a phosphane. Complexes 1 and 2 can be prepared from the efficient one-pot reaction of OsCl3 · 3H2O or [OsCl2(PPh3)3] and the phosphanes iPr2PCH2CH2Y (Y = OMe or NMe2). The reaction with the phosphane iPr2PCH2CO2Me provides an osmium(II) complex which reacts with phenylacetylene to furnish the vinylidene complex 3 in quantitative yield.

    6. Double Open-Edged P10 Dihydrofulvalene as a 16-Electron Donor Ligand (pages 1027–1028)

      Prof. Dr. Otto J. Scherer, Dipl.-Chem. Bernd Höbel and Dr. Gotthelf Wolmershäuser

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210271

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      Two P[BOND]P bonds in the P10 ligand of an allphosphorus analogue of dihydrofulvalene must be opened so that each Rh atom in complex 1 attains 18 valence electrons (structure shown without l,3-C5H3tBu2 ligands). The polycyclic Rh4P10 framework is centrosymmetric.

    7. Stepwise Synthesis of Binuclear Photoactive Complexes with a Bridging 3, 4-Dihy droxyphenylterpyridine Ligand (pages 1028–1030)

      Christine A. Howard and Dr. Michael D. Ward

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210281

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      Heteropolynuclear compounds with photoactive groups can be synthesized in a controlled, stepwise manner, if first the N atoms of the 3,4-dimethoxyphenylterpyridine ligands are coordinated to a RuII complex fragment, then the second binding positions (OR groups) are unmasked and coordinated to a Pd complex fragment. Strong electronic interactions exist between the two parts of the complex in dication 1, which result in interesting photochemical properties.

    8. Tetraphosphafulvalene Dianions: Isoelectronic Species of Tetrathiafulvalene Dications (pages 1031–1032)

      Nicole Maigrot, Dr. Louis Ricard, Dr. Claude Charrier and Prof. Dr. François Mathey

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210311

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      The planar aromatic dianion 1 is formed by the selective cleavage of four P[BOND]C(phenyl) bonds in octaphenyltetraphosphafulvalene with Li or K. The tetraphosphafulvalenes cannot be stacked to give charge-transfer complexes because of the pyramidal environment at the P atoms; however, this is possible with dianion 1. If, for example, 1 is allowed to react with [Cp(xylene)Fe](PF6), each of the five-membered rings is coordinated to a [CpFe]+ fragment.

    9. Diacetoneglucose as Auxiliary Group for the Asymmetric Hetero-Diels–Alder Reaction with Nitrosoalkenes (pages 1033–1035)

      Dipl.-Ing. Thomas Arnold, Dipl.-Ing. Beate Orschel and Prof. Dr. Hans-Ulrich Reissig

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210331

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      Even without complexation effects, sugar auxiliaries can be employed to achieve high asymmetric induction. This is borne out by the highly diastereoselective transformations providing preparatively useful dihydrooxazines 1. The compound 1, R = Ph, was converted into the primary amine 2 (ee > 80%). DAG = diacetoneglucose.

    10. A One-Pot Synthesis of Ketones and Aldehydes from Carbon Dioxide and Organolithium Compounds (pages 1035–1036)

      Dipl.-Chem. Guido Zadel and Prof. Eberhard Breitmaier

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210351

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      Ketones and aldehydes with almost any substitution pattern can be prepared from carbon dioxide according to Reaction (a). By varying the reaction conditions (short reaction time, excess of the alkyllithium compound) certain tertiary alcohols may also be obtained.

    11. The Pentagonal Bipyramid as Fundamental Structure for Compounds with the Coordination Number Seven (pages 1036–1039)

      Dipl.-Chem. Ali-Reza Mahjoub, Thomas Drews and Prof. Dr. Konrad Seppelt

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210361

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      A capped octahedron, a capped trigonal prism, and a pentagonal bipyramid are the three structural types possible for compounds with coordination number 7. TeFmath image, CH3OTeFmath image, and trans-(CH3O)2TeFmath image are all pentagonal bipyramidal; the large methoxy groups take up axial positions. The equatorial F atoms deviate slightly from an ideal plane. The picture on the right shows the crystal structure of TeFmath image, which contains fourfold disordered equatorial fluorine atoms.

    12. Semiconductor-Catalyzed Photoaddition of Cyclic Enol Ethers to 1, 2-Diazenes (pages 1039–1040)

      Dipl.-Chem. Ronald Künneth, Dipl.-Chem. Christian Feldmer and Prof. Dr. Horst Kisch

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210391

      In contrast to the homogeneous reactions, in which the linear addition of aliphatic C[BOND]H bonds to the N[DOUBLE BOND]N group proceeds only with activated diazenes (R1 = R2 = CO2R), the heterogeneous ZnS- and CdS-catalyzed photoaddition takes place also with nonactivated diaryl- and alkylaryl-l,2-diazenes [Eq. (a); e.g. R1 = R2 = Ph; R3H = 3,4-dihydropyran].

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    13. Bis(trisyl)oxadiborirane (pages 1040–1042)

      Prof. Peter Paetzold, Laurence Géret-Baumgarten and Dr. Roland Boese

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210401

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      The oxadiborirane 1 is unexpectedly unreactive. In this molecule the almost linear C[BOND]B[BOND]B[BOND]C chain and very short B[BOND]B distance agree with predictions based on ab initio calculations that suggest that 1 is a diborane(2) RB[DOUBLE BOND]BR with a side-on coordinated O atom. Compound 1 is formed according to Equation (a) in 54 % overall yield. M = Na/K alloy.

    14. Dual Fluorescence of Novel Modified Carotenoids (pages 1042–1044)

      Dr. Hans Bettermann, Dipl.-Chem. Martin Bienioschek, Dipl.-Chem. Hans Ippendorf and Prof. Dr. Hans-Dieter Martin

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210421

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      Despite only a small energy difference between the lowest energy excited singlet states S1 and S2, both the carotenoids 1 and 2 exhibit dual fluorescence. For the first time the energetic position of the S1 state, which is not accessible by UV/VIS excitation, could be estimated. In 1 it lies 3000–3500 cm−l lower than the S2 state; in 2 this gap is 3400–4000 cm−1, which is also presumed to be the S2–S1 difference in β-carotene.

    15. Ten-Membered Ring Enediynes with Remarkable Chemical and Biological Profiles (pages 1044–1046)

      Prof. Dr. K. C. Nicolaou, Erik J. Sorensen, Dr. Robert Discordia, Dr. Chan-Kou Hwang, Prof. Dr. Robert G. Bergman, Robert E. Minto and Dr. Kamal N. Bharucha

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210441

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      The large effects of minimal structural variations are demonstrated by enediynes 1. At 50 °C the cis isomer cyclizes much faster (t1/2 = 4 h) than the trans isomer (t1/2 = 22 h). The carbonate derivative of trans-l is stable even for several hours at 100 °C. The exploration of the chemistry of cyclic enediynes is prompted by their DNA-cleaving properties.

    16. Kinetics of Hydride Transfers from CH, SiH, GeH, and SnH Groups to Carbenium Ions (pages 1046–1048)

      Prof. Dr. Herbert Mayr and Dipl.-Chem. Nils Basso

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210461

      As a hydride donor, tributylstannane is five orders of magnitude more reactive than triphenylsilane as shown in kinetic studies on the hydride-transfer reactions of hydrides of the type HER3 (E = C, Si, Ge, Sn) with diarylcarbenium ions [Eq. (a)]. The reactivity relationship is independent of the electrophilicity of the hydride abstractors and can thus be used as a guide in planning syntheses.

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    17. [RuO(dppz)(tpy)]2+ : a DNA Cleavage Agent with High DNA Affinity (pages 1048–1050)

      Dr. Nishi Gupta, Neena Grover, Dr. Gregory A. Neyhart, Weigen Liang, Dr. Phirtu Singh and Prof. H. Holden Thorp

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210481

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      A RuIVO functional unit and an intercalating heteroligand, dipyridophenazine (dppz), are united in the complex cation of the title, 1, and responsible for its high DNA-cleavage activity and DNA affinity. In the solid state, the units of the RuOH2 analogue of 1 (C1Omath image counterion) are linked by π-stacking interactions similar to those in acridine orange and other conventional intercalators; the distance between the dppz ligands is 3.5 Å. tpy = 2,2′,2″-terpyridine.

    18. Empty Octahedral Hexazirconium Clusters with Only Ten Electrons, [Zr6X14(PR3)4] (pages 1050–1053)

      Dr. F. Albert Cotton, Dr. Xuejun Feng, Dr. Maoyu Shang and William A. Wojtczak

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210501

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      No interstitial atom is found in the Zr6 octahedron of the [Zr6X14(PR3)4] cluster 1 (X = Cl, Br; R = Me, Et, Pr) according to the results of NMR studies, SCF-Xα-SW-MO calculations, and X-ray crystallography (structure here for X = Cl, R = Me, phosphane ligands omitted). In all the clusters examined, four terminal PR3 ligands are bound to the Zr atoms in the equatorial plane, two halogen atoms cap the axial Zr atoms, and all the edges of the octahedron are bridged by halogen atoms. Cluster 1 is synthesized by the reduction of ZrX4 with (nC4H9)3SnH followed by addition of phosphane.

    19. An Organometallic Analogue of the “Criss-Cross” Cycloaddition Reaction (pages 1053–1055)

      Dr. Colleen Kelley, Lisa A. Mercando, Michael R. Terry, Prof. Gregory L. Geoffroy, Dr. Noël Lugan, Zhengtian Xu and Prof. Arnold L. Rheingold

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210531

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      High reactivity characterizes the rhenium vinylidene complex 1, which can function, for example, as a potent 1,3-dienophile in the [3 + 2] cycloaddition with azines: its reaction with PhHC[DOUBLE BOND]N[BOND]N[DOUBLE BOND]CHPh yields the complex 2 (M = Re), which has an almost planar bridging ligand composed of two condensed five-membered rings. [2 + 2] Cycloadditions are also possible as demonstrated by the reaction of 1 with tBuN[DOUBLE BOND]C[DOUBLE BOND]NtBu, which provides isocyanide complexes.

    20. Spirocyclization of a Stable Phosphaalkyne with Aluminum Trichloride—Key Reaction for the Production of Triphospha Dewar Benzene Derivatives (pages 1055–1058)

      Dipl.-Chem. Bernhard Breit, Dipl.-Chem. Uwe Bergsträsser, Prof. Dr. Gerhard Maas and Prof. Dr. Manfred Regitz

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210551

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      In a highly selective reaction the spirocyclotrimer 2 is formed when the phosphaalkyne 1 is treated with the Lewis acid AlCl3. The diphosphet is released when dimethyl sulfoxide (DMSO) is added, and it subsequently rearranges to 1,3,5-triphospha Dewar benzene by cleavage of the P[BOND]P bond in the diphosphirene unit. This can be trapped with 1 by a homo–Diels–Alder reaction leading to the formation of the tetraphosphacubane 3. All these reaction steps are novel.

    21. Cyclopentadienyl Cobalt Complexes of Cobalta-pentalenes: Products Formed by Reaction of (μ-Cyclopentadienylidene) Cobalt Complexes with Silylalkynes (pages 1058–1060)

      Priv.-Doz. Dr. Hubert Wadepohl, Dr. Wolfgang Galm, Dr. Hans Pritzkow and Dipl.-Chem. Andreas Wolf

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210581

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      Unusual Co2 complexes like 1 with a cobaltabicyclic unit constructed from a planar CoC4 and a folded C5 ring are formed in the reaction of 2 with certain silylalkynes by (alkyne)C[BOND]Si bond cleavage and a hydrogen shift. The insertion of the alkynes into the M[DOUBLE BOND]C bond characteristic of reactions with Fischer or Schrock carbene complexes is not observed with 2; which contains a cyclopentadienylidene ligand.

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    22. Synthesis of (2-Arylindol-3-yl)acetamides as Probes of Mitochondrial Steroidogenesis—A New Mechanism for GABAA Receptor Modulation (pages 1060–1062)

      Prof. Alan P. Kozikowski, Dr. Dawei Ma, Elena Romeo, Dr. James Auta, Dr. Vissilios Papadopoulos, Dr. Gulia Puia, Erminio Costa and Alessandro Guidotti

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210601

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      High affinity and selectivity for mitochondrial DBI receptors characterize indolylacetamides 1. These compounds stimulate the production of neurosteroids in glial cells allowing possible indirect modulation of the γ-aminobutyric acid receptor complex. In behavioral experiments with rats, 1a was found to have antineophobic action, that is, it reduces the fear of novelty.

    23. Dependence of the Reactivity of Ag and Ni Clusters Deposited on Solid Substrates on the Cluster Size (pages 1062–1064)

      Prof. Dr. C. N. Ramachandra Rao, Venugopal Vijayakrishnan, Asok Kumar Santra and Menno W. J. Prins

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210621

      Bulk silver and nickel are less reactive than small clusters of these elements, as reactivity studies with O2 as well as with H2S and CO prove. The dissociation of O2 on small Ag clusters is favored, and the proportion of O2 molecules cleaved does not depend upon temperature, as is the case for larger clusters and silver metal. The change in reactivity is greatest at the metal–insulator transition—a finding that has implications for heterogeneous catalysis.

    24. A Simple Method for the Replacement of the OH Group in Free Carboxylic Acids by the Phosphonium Ylide Group (pages 1064–1066)

      Prof. Dr. Hans Jürgen Bestmann, Dr. Roman Dostalek and Dipl.-Chem. Bernd Bauroth

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210641

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      Acyl ylides and hexamethyldisiloxane are produced in the one-pot reaction of free carboxylic acids with bis(trimethylsilyl)methylenetriphenylphosphorane [Eq. (a)]. Dicarboxylic acids and amino acids also undergo this reaction; only O-protected tartaric acids and monomethyl tartrates yield undefined elimination products.

    25. Inhibition of the [2 + 2 + 2] Cyclization by the Formation of Chelates: Alkyne and Vinylidene Complexes with Cyclopentadienylcobalt(I) (pages 1066–1068)

      Priv.-Doz. Dr. Holger Butenschön, Dr. Ralf T. Kettenbach and Prof. Dr. Carl Krüger

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210661

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      The trimerization of alkynes to arenes usually observed in the reaction of cyclopentadienyl-cobalt(I) complexes with alkynes could be prevented by chelation of the metal center with a “phosphane arm” on the cyclopentadienyl ligand. Instead alkyne complexes were obtained in very good yields. The reaction with ethyne leads to the vinylidene complex 1 (88 % yield), a possible precursor to the carbene–cobalt complex.

    26. Reduction of Dispersed Indigo Dye by Indirect Electrolysis (pages 1068–1069)

      Dr. Thomas Bechtold, Dr. Eduard Burtscher, Angelika Amann and Prof. Ortwin Bobleter

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210681

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      Triethanolamine–iron complexes mediate the electrolysis of dispersed indigo (1) in aqueous alkaline solution to the leuko compound, which is soluble in this medium. This is a central step in the application of indigo as a textile dye. Since conventional reducing agents such as Na2S2O4 cannot be recovered and the process baths cannot be recycled, this new “rechargeable” reducing agent is of great environmental interest.

    27. C36H36—Tetrahedral Clamping of Four Benzene Rings in a Spherical Hydrocarbon Framework (pages 1069–1071)

      Prof. Dr. Fritz Vögtle, Dipl.-Chem. Jens Gross, Dr. Christian Seel and Dr. Martin Nieger

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210691

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      A chiral P-helical conformation is revealed for the 1:1 adduct of the spherical, heptacyclic hydrocarbon C36H361 (spheriphane) and CHCl3, in which the CHCl3 guest molecule is bound to one of the four benzene rings by a short-range H–π interaction. The intramolecular cavity of 1 with a diameter of 568 pm is large enough for metal cations to fit inside.

    28. Diastereoselective Synthesis of Substituted Cyclohexadienes from Enantiomerically Pure Tricarbonyl(2-pheny1-4, 5-dihydrooxazole)chromium Complexes (pages 1071–1073)

      Prof. Dr. Ernst Peter Kündig, Dr. Alberto Ripa and Dr. Gérald Bernardinelli

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210711

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      Two or, as shown here, three organic groups can be added with high diastereoselectivity to a π bond in benzene [Eq. (a)]. This one-pot procedure relies on the combined effects of two auxiliaries on the arene: a chiral, σ-bound heterocycle and a π-bound metal complex fragment.

    29. Strain-Activated Formation of a Triple-Layered Phane (pages 1073–1074)

      Prof. Dr. Henning Hopf, Dipl.-Chem. Bernhard Witulski, Dipl.-Chem. Peter Bubenitschek and Prof. Dr. Peter G. Jones

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210731

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      In a simple, high-yielding reaction the triple-layered compound 2 is obtained from cyclophane 1 by Lewis acid catalyzed dimerization and subsequent aromatization of the central six-membered ring. The reaction allows access to interesting multilayered arenes, and the intramolecular interactions of such π-electron systems can now be studied.

    30. Nitrocalix [4]arenes as Molecules for Second-Order Nonlinear Optics (pages 1075–1077)

      Drs. Erik Kelderman, Dr. Willem Verboom, Dr. Johan F. J. Engbersen, Prof. Dr. Ir. David N. Reinhoudt, Ir. Gerard J. T. Heesink, Dr. Niek F. van Hulst, Drs. Lode Derhaeg and Prof. Dr. Andre Persoons

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210751

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      The frequency-doubling of 820nm laser light is one of the properties of a series of nitrocalix-[4]arenes making them suitable, in principle, for the construction of a blue laser. Derivative 1 is the most promising, since it displays the greatest hyperpolarizability and the largest dipole moment and is stable as a film in a polymer matrix for long periods.

    31. [{Cp*Cr(μ3-H)}4]—a Paramagnetic Chromium Hydride with a Cubane Structure (pages 1077–1079)

      Robert A. Heintz, Brian S. Haggerty, Prof. Dr. Arnold L. Rheingold, Prof. Dr. Klaus H. Theopold and Hong Wan

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210771

      Thumbnail image of graphical abstract

      For the exploration of the organometallic chemistry of divalent chromium, the readily synthesized CrII complex 1 is a simple starting material. The chloro bridges can be exchanged for alkyl groups (R = Me, nBu, CH2SiMe3), and the resulting complexes 2 react with H2 to give the tetranuclear hydrido complex 3 with a cubane structure. Unexpectedly, 3 shows almost ideal Curie paramagnetism according to magnetic measurements.

    32. A Short Diastereoselective Entry to Indole Alkaloids of the Corynanthe Type by the Intramolecular Ene Reaction (pages 1079–1080)

      Prof. Dr. Lutz F. Tietze and Dr. Jürgen Wichmann

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210791

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      Biologically active indole alkaloids are accessible in a convergent and stereoselective fashion by the sequential intramolecular ene reaction of starting compounds such as 1. The first cyclization to 2 in this one-pot procedure is triggered by trifluoroacetic acid, the second by SnCl4.

    33. Synthesis and Structure of a Mononuclear η2-Hydrazine Complex by Protonation of an [N2H2]2− Complex (pages 1081–1082)

      Prof. William J. Evans, Dr. Gabriele Kociok-Köhn and Dr. Joseph W. Ziller

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210811

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      The synthetic route to the η2-hydrazine–samarium complex 1 parallels protonations which were postulated for the N2 fixation in biological systems. Thus 1 was formed by a double H +-transfer onto the bridging (N2H2)2− ligand of the dinuclear complex 2. The hydrazine ligand is bound firmly to the Sm center and cannot be removed by either vacuum or recrystallization in potentially coordinating solvents.

      • equation image
    34. Reduction of a Boron–Nitrogen 1,3-Butadiene Analogue: Evidence for a Strong B[BOND]B π-Bond (pages 1082–1083)

      Afarin Moezzi, Ruth A. Bartlett and Professor Philip P. Power

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210821

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      An ethene analogue with a B[DOUBLE BOND]B bond and two negatively charged boron centers (2) is formed from the reduction of 1 with lithium powder to 2-2 Li. Based on UV data, the B[DOUBLE BOND]B bond energy is estimated at 40 kcal mol−1. This double bond is formed at the expense of two B[DOUBLE BOND]N bonds in 1, as reflected in the significant lengthening of the B[DOUBLE BOND]N bonds on transition from 1 to 2.

    35. Synthesis of (R)- and (S)2-tert-Butyl-6-trifluoro-methyl-1,3-dioxin-4-ones, Transformations into 3-Hydroxy-3-(trifluoromethyl)alkanoates, and Surprising Differences in the Reactivity of CH3- and CF3-Substituted Compounds (pages 1083–1085)

      Dipl.-Chem. Markus Gautschi and Prof. Dr. Dieter Seebach

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210831

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      A surprising inversion of the stereo- and regioselectivity on changing from CH3 to CF3 derivatives is found in the bromination of the appropriate enolates as shown by the products 1 and 2. Furthermore, the conjugate addition of the benzyl group to the related dioxinones leads to 3 and 4. The mechanistic implications of these findings is not yet clear.

    36. Synthesis of Cubane-like and Double Cubane-like Tungsten-Copper-Sulfur Clusters from the “Butterfly” Cluster [Cu2S3W(O)(PPh3)3] (pages 1085–1087)

      Shaowu Du, Nianyong Zhu, Pengcheng Chen and Prof. Xintao Wu

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210851

      The denticity of the thiolato ligand decides whether the cubane-like cluster 1 or the bicubane-like cluster 2 is obtained in the reaction of copper thiolates with the “butterfly” cluster [Cu2S3W(O)(PPh3)3]. This could also be confirmed by further cluster syntheses. Tungsten–copper–sulfur clusters such as 1 and 2 are of interest, inter alia, as models for the active centers of some enzymes.

      • equation image
    37. Docking of a Second Functional Protein Layer to a Streptavidin Matrix on a Solid Support: Studies with a Quartz Crystal Microbalance (pages 1087–1090)

      Dipl.-Chem. Wolfgang Müller, Prof. Dr. Helmut Ringsdorf, Dr. Peter Suci, Dr. James N. Herron, Dipl.-Chem. Hiroshi Ebato and Prof. Dr. Yoshio Okahata

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210871

      Thumbnail image of graphical abstract

      A long, flexible, hydrophilic spacer is needed in the biotinlipid for the specific binding of the protein streptavidin to the lipid-containing membrane. This was shown by measurements with a quartz crystal microbalance, which indicated that 1 was specifically binding. The binding of a second protein layer of biotinylated Fab fragment to the streptavidin matrix could also be monitored in real time by this method.

    38. A Remarkable Change in Framework Cation Positions upon Lithium Exchange: the Crystal Structure of LiMnPO4(OH) (pages 1090–1092)

      Dr. Miguel A. G. Aranda, Prof. Dr. Sebastian Bruque and Dr. J. Paul Attfield

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210901

      Thumbnail image of graphical abstract

      A migration of Mn3+ ions into previously unoccupied octahedral holes, while the oxygen and the phosphorus sites remain virtually unchanged, takes place in the course of the reaction of MnPO4. H2O with LiNO3 to give the title compound (see polyhedral representation right; Li atoms as open circles, MnO6 octahedra and PO4 tetrahedra, H atoms omitted). These crystal-chemical effects are surprising, but such topotactic reactions are also of interest for the preparation of novel materials, for example for batteries and ionic conductors.

    39. The 31P-NMR Spectroscopic Determination of the Enantiomeric Excess of Unprotected Amino Acids (pages 1092–1093)

      Ron Hulst, Prof. Dr. Ben L. Feringa and Dr. N. Koen de Vries

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210921

      Thumbnail image of graphical abstract

      No separation is needed! The enantiomeric excess of unprotected amino acids can be determined very reliable by 31PNMR spectroscopy after derivatization as phosphonic amides 1. This rapid and simple analytical procedure, suitable for aqueous solutions, is also applicable for amino acid derivatives, chiral amines, and alcohols.

    40. A Diels–Alder Route to [5]- and [6]-Helicenes (pages 1093–1095)

      Nikolaos D. Willmore, Dr. Longbin Liu and Prof. Thomas J. Katz

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210931

      Thumbnail image of graphical abstract

      The reaction of acetophenone enol ethers with benzoquinone [Eq. (a)] furnishes functionalized [6]helicenes easily, quickly, in high yields, and on a large scale. This reaction has many advantages over alternative synthetic routes such as the photocyclization of stilbenes.

  4. Book Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Book Review: Quanta. A Handbook of Concepts. 2nd Edition. P. W. Atkins (pages 1095–1096)

      Wolfram Sander

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210951

    2. Book Review: The Green Flame: Surviving Government Secrecy. By A. Dequasie (pages 1096–1097)

      George B. Kauffman

      Article first published online: 22 DEC 2003 | DOI: 10.1002/anie.199210962

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