Angewandte Chemie International Edition

Cover image for Vol. 43 Issue 21

May 17, 2004

Volume 43, Issue 21

Pages 2727–2863

    1. Cover Picture: Efficient Asymmetric Hydrogenation of Pyridines (Angew. Chem. Int. Ed. 21/2004) (page 2727)

      Frank Glorius, Nick Spielkamp, Sigrid Holle, Richard Goddard and Christian W. Lehmann

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200490062

      The stereoselective hydrogenation of oxazolidinone-substituted pyridines shown in the cover picture gives piperidines containing up to four new stereocenters. One of the biologically active compounds readily accessible by this method is (S)-coniine, the poisonous hemlock alkaloid used in ancient Greece for executions. The famous painting by David shows Socrates shortly before drinking from the poison chalice. F. Glorius et al. describe this synthetic method on pages 2850 ff.

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      Dianions of Tetraboranes(4): Puckered Aromatic Four-Membered Rings and Their Reactions with Conservation of Aromaticity (page 2737)

      Wahid Mesbah, Carsten Präsang, Matthias Hofmann, Gertraud Geiseler, Werner Massa and Armin Berndt

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200490064

    3. Micrometer-to-Nanometer Replication of Hierarchical Structures by Using a Surface Sol–Gel Process (pages 2746–2748)

      Rachel A. Caruso

      Version of Record online: 3 MAY 2004 | DOI: 10.1002/anie.200301747

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      The sol–gel process has been shown to replicate materials with high precision on both the micro- and nanometer scales. Paper, cotton, and cloth templates combine with a surface sol–gel process in order to maintain details of hierarchical structural properties by producing a self-supporting material consisting of interwoven and branched tubes that result from fibers less than 100 nm in diameter (see SEM image; scale bar=2 μm).

    4. A New Hydrosilylation Mechanism—New Preparative Opportunities (pages 2749–2750)

      Henri Brunner

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200301742

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      One up in limiting reactivity: The monosubstitution of multifunctional molecules is a general problem in synthetic chemistry. The catalyst [Cp*(PiPr3)(H)2Ru[DOUBLE BOND]Si(H)Ph⋅Et2O][B(C6F5)4] (Cp*=η5-C5Me5) can be used for the alkylation of phenylsilane PhSiH3 with simple olefins. The reaction stops at the monoalkylation level to give PhSi(Alk)H2 (see scheme; R=H, C6H5, C4H9).

    5. Chemically Catalyzed Asymmetric Cyanohydrin Syntheses (pages 2752–2778)

      Jean-Michel Brunel and Ian P. Holmes

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200300604

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      Versatile synthetic intermediates: Chiral cyanohydrins (see formula) can be readily converted into a number of key functional groups with control of absolute stereochemistry. Advances in chemically catalyzed asymmetric cyanation reactions of aldehydes and ketones to form cyanohydrins are described and compared.

    6. Shear Patterning of Microdominos: A New Class of Procedures for Making Micro- and Nanostructures (pages 2780–2783)

      Byron D. Gates, Qiaobing Xu, Venkat R. Thalladi, Tingbing Cao, Tanya Knickerbocker and George M. Whitesides

      Version of Record online: 2 APR 2004 | DOI: 10.1002/anie.200353009

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      A simple technique for fabricating complex, repetitive 3D microstructures, and the application of this procedure to the generation of arrays of nanoscale (in-plane) features is described. This technique, which involves the use of shearing forces, is capable of fabricating regular, 3D arrays of microstructures that are difficult or impossible to obtain by other methods (see picture).

    7. Well-Defined Carbon Nanoparticles Prepared from Water-Soluble Shell Cross-linked Micelles that Contain Polyacrylonitrile Cores (pages 2783–2787)

      Chuanbing Tang, Kai Qi, Karen L. Wooley, Krzysztof Matyjaszewski and Tomasz Kowalewski

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200353401

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      An alternative approach to nanostructured carbon materials relies on the use of covalently stabilized micellar precursors that are soluble in aqueous systems (see picture). These precursors belong to a class of shell cross-linked nanoparticles (SCKs) that are formed by self-assembly and stabilization of amphiphilic block copolymers.

    8. [SiNb12O40]16− and [GeNb12O40]16−: Highly Charged Keggin Ions with Sticky Surfaces (pages 2787–2792)

      May Nyman, François Bonhomme, Todd M. Alam, John B. Parise and Gavin M. B. Vaughan

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200353410

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      The α-Keggin ions [TNb12O40]16− (T=Si, Ge) have been synthesized hydrothermally as water-soluble sodium salts. These clusters are very highly charged, and are bound to their charge-balancing sodium atoms in the solid state (see picture). NMR spectroscopy experiments show that the sodium atoms remain strongly associated with the clusters in solution.

    9. A Family of Supramolecular Frameworks of Polyconjugated Molecules Hosted in Aromatic Nanochannels (pages 2792–2797)

      Piero Sozzani, Angiolina Comotti, Silvia Bracco and Roberto Simonutti

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200353479

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      Aromatic nanochannels were assembled about linear π-conjugated molecules. The novel supramolecular architectures are cemented by weak interactions and form crystals that melt at much higher temperatures than the standard molecular arrangement. The perfect fitting of the chains in the unusual environment is shown by the close contacts of 2.5 Å that occur between guest hydrogen atoms and the surrounding aromatic groups (see picture).

    10. A Robust Porous Material Constructed of Linear Coordination Polymer Chains: Reversible Single-Crystal to Single-Crystal Transformations upon Dehydration and Rehydration (pages 2798–2801)

      Eun Young Lee and Myunghyun Paik Suh

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200353494

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      Hole in one: A metal–organic framework with permanent microporosity has been constructed from linear coordination polymer chains consisting of [Ni(cyclam)]2+ and bpydc2−. In framework 1 the chains run in three directions (red, green, blue in the picture) and are stacked to form 1D channels that are filled with water molecules, which can be removed completely and reabsorbed with retention of the single crystallinity.

    11. A Dimeric Manganese(III) Tetradentate Schiff Base Complex as a Single-Molecule Magnet (pages 2801–2805)

      Hitoshi Miyasaka, Rodolphe Clérac, Wolfgang Wernsdorfer, Lollita Lecren, Claire Bonhomme, Ken-ichi Sugiura and Masahiro Yamashita

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200353563

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      Slow relaxation of the magnetization reveals the single-molecule magnetic behavior of [Mn2(saltmen)2(ReO4)2] (saltmen2−=N,N′-(1,1,2,2-tetramethylethylene)bis(salicylideneiminate), a simple, out-of-plane MnIII dimeric complex containing a [MnIII(μ-O)2MnIII] core (see structure shown, Mn brown, O red, N blue, Re pink). The two anisotropic MnIII ions are ferromagnetically coupled, which induces an ST=4 ground state.

    12. Light-Activated Transfer of Nitric Oxide from a Porous Material (pages 2806–2809)

      Jeremy T. Mitchell-Koch, Timothy M. Reed and A. S. Borovik

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200352881

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      A light-dark-light-dark sequence was used to demonstrate that only NO is released from a new mesoporous material that contains immobilized Ru(NO) sites. No release is observed during the dark phases (shown schematically). Since this release is regulated by light, the controlled transfer of NO to cobalt(II) tetraphenylphorphyrin as well as equine skeletal muscle myoglobin is possible.

    13. Enzymatic Synthesis of Redox-Labeled RNA and Dual-Potential Detection at DNA-Modified Electrodes (pages 2809–2812)

      Daniel A. Di Giusto, Wjatschesslaw A. Wlassoff, Susanne Giesebrecht, J. Justin Gooding and Garry C. King

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200352977

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      Ferrocene and anthraquinone were used to label RNA (red, dark blue), which could then be detected at an electrode surface bearing complementary DNA oligonucleotide probes (light blue). This approach is an electrochemical analog of popular fluorescence methods for gene expression analysis.

    14. Reductive Electrochemical Cyclization of a Photochromic 1,2-Dithienylcyclopentene Dication (pages 2812–2815)

      Brian Gorodetsky, Hema D. Samachetty, Robert L. Donkers, Mark S. Workentin and Neil R. Branda

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200353029

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      Getting the blues: Electrochemical ring-closing is observed for the photochromic bis(pyridinium) dication of the dithienylethene backbone in which the pale yellow ring-open isomer can be converted to its blue ring-closed isomer by either irradiation with UV light or by electrochemical reduction (see picture). The electrochemical ring-closing reaction also produces a photochemically unobtainable product.

    15. Asymmetric Hydrogenation of Ketones Catalyzed by RuII–bicp Complexes (pages 2816–2819)

      Daniel G. Genov and David J. Ager

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200353441

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      Variations on a theme: A RuII–bicp complex used in combination with an achiral 2-(alkylthio)amine ligand (or achiral 1,2-diamine ligand) is an efficient catalyst for the highly enantioselective hydrogenation of a variety of ketones (see scheme). In some cases simply changing the amine ligand and/or the solvent leads to opposite enantioselectivity.

    16. Nanoporous Metal-Containing Nickel Phosphates: A Class of Shape-Selective Catalyst (pages 2819–2822)

      Jong-San Chang, Jin-Soo Hwang, Sung Hwa Jhung, Sang-Eon Park, Gérard Férey and Anthony K. Cheetham

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200353502

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      A substitute for zeolites: The nanoporous nickel phosphate VSB-1 exhibits zeolitic properties and very weak acidity and basicity (see picture). When VSB-1 is modified by metal-ion exchange or through metal incorporation into the framework, it offers promising catalytic properties, such as shape selectivity, and activity in both redox catalysis and photocatalysis.

    17. Synthesis of Rimocidinolide Methyl Ester, the Aglycone of (+)-Rimocidin (pages 2822–2826)

      Garrick K. Packard, Yueqing Hu, Andrea Vescovi and Scott D. Rychnovsky

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200453697

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      An efficient, convergent route based on cyanohydrin acetonide couplings was used for the synthesis of the aglycone of rimocidin, rimocidinolide methyl ester (1). Cyanohydrin acetonides were used as β-hydroxyketone synthetic equivalents in the assembly of the polyol chain.

    18. A 4-exo-dig Cyclocarbopalladation/8π Electrocyclization Cascade: Expeditious Access to the Tricyclic Core Structures of the Ophiobolins and Aleurodiscal (pages 2826–2830)

      Bahaâ Salem and Jean Suffert

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200453773

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      New perspectives for an unpopular reaction? An 8π electrocyclization has been used to construct the eight-membered ring of 5,8,5- and 6,4,8,5-polycyclic systems in a one-pot 4-exo-dig cyclocarbopalladation/Stille coupling/electrocyclization sequence (see scheme). The polycycles obtained have the framework of biologically important compounds such as the ophiobolins. R=Et, Me; n=0, 1.

    19. The Transition State of Thermal Organic Reactions: Direct Observation in Real Time (pages 2830–2834)

      D. Hern Paik, Ding-Shyue Yang, I-Ren Lee and Ahmed H. Zewail

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200453962

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      A classic in physical organic chemistry, the inversion of cyclooctatetraene (COT), was studied with femtosecond resolution by negative-ion-beam techniques. The transition state for the thermal inversion was accessed directly by detachment of the electron from the planar COT ion.

    20. Identifying Specific Conformations by Using a Carbohydrate Scaffold: Discovery of Subtype-Selective LPA-Receptor Agonists and an Antagonist (pages 2834–2837)

      Yoko Tamaruya, Masato Suzuki, Goshu Kamura, Motomu Kanai, Kotaro Hama, Kumiko Shimizu, Junken Aoki, Hiroyuki Arai and Masakatsu Shibasaki

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200454065

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      Stable and potent subtype-selective lysophosphatidic acid (LPA) analogues (agonists and an antagonist) were developed by using carbohydrates as a core structure (see scheme). An array of molecules with the recognition motifs of LPA (a phosphate anion, an oleoyl group, and a hydrogen-bond acceptor) attached to carbohydrate isomers in different three-dimensional arrangements were tested for LPA-receptor activation or inhibition. R=alkyl.

    21. MOCVD-Loading of Mesoporous Siliceous Matrices with Cu/ZnO: Supported Catalysts for Methanol Synthesis (pages 2839–2842)

      Ralf Becker, Harish Parala, Frank Hipler, Olga P. Tkachenko, Konstantin V. Klementiev, Wolfgang Grünert, Hagen Wilmer, Olaf Hinrichsen, Martin Muhler, Alexander Birkner, Christof Wöll, Sven Schäfer and Roland A. Fischer

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200351166

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      Consecutive vaporization cycles for the preparation of heterogeneous catalysts: Active Cu- and ZnO-containing methanol-synthesis catalysts were obtained by vaporizing suitable organometallic precursors into mesoporous silicates, followed by thermal treatment (see scheme). The catalytically active components in the final material have nanoscopic dimensions. The methanol production by the catalysts is similar to that of systems synthesized by the classical route.

    22. Bis(fluoroformyl)trioxide, FC(O)OOOC(O)F (pages 2843–2846)

      Holger Pernice, Michael Berkei, Gerald Henkel, Helge Willner, Gustavo A. Argüello, Michael L. McKee and Thomas R. Webb

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200353369

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      Three of a kind: The open-chain trioxide bis(fluoroformyl)trioxide, FC(O)OOOC(O)F, is prepared on preparative scale by treating CO with F2 in an oxygen atmosphere (see scheme; F green, O blue, C gray). The unstable FC(O)OOOC(O)F is characterized fully including X-ray diffraction. In the crystal structure the most stable rotamer (trans-syn-syn) is present as only one of two possible chiral helical molecules.

    23. Intramolecular C[BOND]H Activation in Complexes with Mo[BOND]Bi Metal Bonds (pages 2846–2849)

      Stefan Roggan, Christian Limberg, Burkhard Ziemer and Marcus Brandt

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200353576

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      Banana bonds” between Bi and C are a feature of 2, which forms in the course of intramolecular alcohol eliminations from 1. C[BOND]H activations through complex-induced proximity effects are responsible for these unexpected eliminations.

    24. Efficient Asymmetric Hydrogenation of Pyridines (pages 2850–2852)

      Frank Glorius, Nick Spielkamp, Sigrid Holle, Richard Goddard and Christian W. Lehmann

      Version of Record online: 28 APR 2004 | DOI: 10.1002/anie.200453942

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      Up to four stereocenters can be created efficiently in a single step by the asymmetric hydrogenation of oxazolidinone-substituted pyridines (see scheme). Furthermore, selective chirality transfer and nondestructive cleavage of the chiral auxiliary occur under the same reaction conditions, making an additional cleavage step unnecessary.

    25. Determination of the Absolute Chirality of Adsorbed Molecules (pages 2853–2856)

      Roman Fasel, Joachim Wider, Christoph Quitmann, Karl-Heinz Ernst and Thomas Greber

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200353311

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      Intramolecular “electron lamp” throws bright shadows: Angle-scanned X-ray photoelectron diffraction (XPD) allows the absolute configuration of adsorbed molecules to be determined in a straightforward way. Owing to intramolecular scattering, the C 1s XPD pattern of tartaric acid adsorbed on Cu(110) (see picture; Cu brown, C blue, O red) has pronounced forward-focusing maxima that directly yield the absolute molecular conformation without the need for complex calculations.

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      Preview: Angew. Chem. Int. Ed. 21/2004 (page 2863)

      Version of Record online: 12 MAY 2004 | DOI: 10.1002/anie.200490065