Angewandte Chemie International Edition

Cover image for Vol. 42 Issue 9

March 3, 2003

Volume 42, Issue 9

Pages 957–1069

    1. Cover Picture: Molecular Mousetraps: Gas-Phase Studies of the Covalent Coupling of Noncovalent Complexes Initiated by Reactive Carbenes Formed by Controlled Activation of Diazo Precursors (Angew. Chem. Int. Ed. 9/2003) (page 957)

      Ryan R. Julian, Jeremy A. May, Brian M. Stoltz and J. L. Beauchamp

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390276

      Molecular mousetraps are an unprecedented class of host–guest reagents. In the example shown in the cover picture, 18-crown-6 ether is utilized as the “bait” to attract target molecules with a protonated primary amine functional group. Appropriate activation of the noncovalent complex springs the diazo “trap”, which leads to covalent attachment of the two molecules depicted in the reaction scheme. The research is detailed in the Communication by J. L. Beauchamp, B. M. Stoltz et al. on page 1012 ff.

    2. Graphical Abstract: Angew. Chem. Int. Ed. 9/2003 (pages 960–967)

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390277

    3. Web Site: Science: Viewing La Vega (page 968)

      Pankaz K. Sharma and Sason Shaik

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390278

    4. Möbius Strips of NbSe3: Morphology Design and Solid-State Chemistry (pages 972–974)

      Greta R. Patzke

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390282

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      A preparative challenge in inorganic solid-state synthesis is to control the morphology of the arising products, for example, of vaterite microsponges (see picture). An important breakthrough in this area has now been achieved with the preparation of microcrystalline Möbius strips and rings from niobium selenide. The synthesis was achieved by a versatile combination of chemical transport reactions and templating techniques.

    5. Proline-Catalyzed Asymmetric α-Amination of Aldehydes and Ketones—An Astonishingly Simple Access to Optically Active α-Hydrazino Carbonyl Compounds (pages 975–978)

      Rudolf O. Duthaler

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390283

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      Simple, direct, and highly enantioselective α-amination of carbonyl compounds 1 with azodicarboxylates 2 no longer requires prior enolization of the substrate. The “magic” small-organic-molecule catalyst for this reaction in dichloromethane at room temperature is once again L-proline (3).

    6. Organic Templates for the Generation of Inorganic Materials (pages 980–999)

      Kjeld J. C. van Bommel, Arianna Friggeri and Seiji Shinkai

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390284

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      Shapely structured inorganic materials of diverse morphologies and compositions are nowadays obtainable through the transcription of organic templates (see picture). This review gives an overview of the various kinds of templates, precursors, and methods that have been employed for this purpose, as well as the diversity of inorganic materials that have been obtained.

    7. Metallacarborane-Based Nanostructures: A Carbon-Wired Planar Octagon (pages 1002–1005)

      Haijun Yao, Michal Sabat, Russell N. Grimes, Fabrizia Fabrizi de Biani and Piero Zanello

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390255

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      A planar C16B8octagonal macrocycle that incorporates four identical metallacarborane units, linked by four diethynyl chains, has been prepared from a monomeric cobaltacarborane through a designed multistep synthesis (see picture). The air-stable molecule undergoes stepwise electrochemical reduction in THF solution to generate mono-, di-, and tetraanions, with the cyclic and square-wave voltammetric data indicating significant electron delocalization in the ring system.

    8. Preparation of Artificial Metalloenzymes by Insertion of Chromium(III) Schiff Base Complexes into Apomyoglobin Mutants (pages 1005–1008)

      Masataka Ohashi, Tomomi Koshiyama, Takafumi Ueno, Manabu Yanase, Hiroshi Fujii and Yoshihito Watanabe

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390256

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      Insertion of a symmetric metal complex, [CrIII(5,5′-tBu-salophen)]+ (H2salophen=N,N′-bis(salicylidene)-1,2-phenylenediamine), into the active site of apomyoglobin is demonstrated (see picture). The metal ion and the ligand structure are very important factors that influence the binding affinity of the metal complex with the myoglobin (Mb) cavity. Semisynthetic metalloenzymes can catalyze enantioselective sulfoxidation by using the chiral protein cavity.

    9. Oligonucleotide-Templated Self-Assembly of Nucleotide Bolaamphiphiles: DNA-Like Nanofibers Edged by a Double-Helical Arrangement of A–T Base Pairs (pages 1009–1012)

      Rika Iwaura, Kaname Yoshida, Mitsutoshi Masuda, Mayumi Ohnishi-Kameyama, Mitsuru Yoshida and Toshimi Shimizu

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390257

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      A stack with a twist is formed when a thymidine bolaamphiphile (green rod with red ends in the scheme) is allowed to interact with strands of oligoadenylic acid (purple chain with yellow pentagons) in aqueous solution. Complementary A–T hydrogen bonding leads to nanofibers having a DNA-like double helix.

    10. Molecular Mousetraps: Gas-Phase Studies of the Covalent Coupling of Noncovalent Complexes Initiated by Reactive Carbenes Formed by Controlled Activation of Diazo Precursors (pages 1012–1015)

      Ryan R. Julian, Jeremy A. May, Brian M. Stoltz and J. L. Beauchamp

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390258

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      The covalent linking of noncovalently bound host–guest complexes in the gas phase is achieved by the formation of a highly reactive carbene from the host molecule, which is generated by collision-activated dissociation. Possible mechanisms for the resulting intermolecular reactions are explored by theory and experiment.

    11. A Rare-Earth Metal TCNQ Magnet: Synthesis, Structure, and Magnetic Properties of {[Gd2(TCNQ)5(H2O)9][Gd(TCNQ)4(H2O)3]}⋅4 H2O (pages 1015–1018)

      Hanhua Zhao, Mervin J. Bazile, Jr., José R. Galán-Mascarós and Kim R. Dunbar

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390259

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      A lanthanide/organic radical based molecular magnet (Tc=3.5 K) has been prepared from a reaction of GdCl3⋅6 H2O with Li[TCNQ] (TCNQ=7,7,8,8-tetracyanoquinodimethane). The title compound was structurally characterized by single-crystal X-ray diffraction and contains distinct anionic and cationic (see picture) networks containing Gd, TCNQ, and H2O in different ratios.

    12. Direct Liquid-Phase Sulfonation of Methane to Methanesulfonic Acid by SO3 in the Presence of a Metal Peroxide (pages 1019–1021)

      Sudip Mukhopadhyay and Alexis T. Bell

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390260

      Activation of methane by metal peroxides: Calcium peroxide serves as an effective radical initiator in the liquid-phase sulfonation of methane to methansulfonic acid (MSA) by SO3 [Eq. (1)]. Under the best reaction conditions a 91 % conversion of SO3 to MSA was achieved.

      • equation image
    13. Control of α/β Stereoselectivity in Lewis Acid Promoted C-Glycosidations Using a Controlling Anomeric Effect Based on the Conformational Restriction Strategy (pages 1021–1023)

      Satoru Tamura, Hiroshi Abe, Akira Matsuda and Satoshi Shuto

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390261

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      The kinetic anomeric effect has been used to control both α and β stereoselectivity in glycosidation reactions. Depending on the restricted conformation 4C1 or 1C4 of the substrate, the anomeric α (1[RIGHTWARDS ARROW]2) or β product (3[RIGHTWARDS ARROW]4) was obtained highly stereoselectively from the Lewis acid promoted anomeric allylation with allyltrimethylsilane (TIPS=triisopropylsilyl).

    14. An Unexpected, Sterically Driven, Methyl Halide Elimination in Pentacoordinate Siliconium Halide Salts: Silicon Complexes with Equatorial Nitrogen Coordination (pages 1023–1026)

      Daniel Kost, Boris Gostevskii, Nikolaus Kocher, Dietmar Stalke and Inna Kalikhman

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390262

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      Sterically hindered pentacoordinate tert-butylsiliconium halide complexes undergo methyl halide elimination. The products have one covalent and one dative N[BOND]Si bond, both in the unprecedented equatorial position. A complete pseudorotation coordinate is demonstrated with suitable crystal structures.

    15. Oxidation of Unactivated Primary Aliphatic Amines Catalyzed by an Electrogenerated 3,4-Azaquinone Species: A Small-Molecule Mimic of Amine Oxidases (pages 1026–1029)

      Martine Largeron, Anne Neudorffer and Maurice-Bernard Fleury

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390263

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      High catalytic performance of the electrogenerated amine oxidase mimic 3,4-iminoquinone 1ox is observed under metal-free conditions in the chemoselective oxidation reaction of unactivated primary aliphatic amines.

    16. Efficient Degradation of Organic Pollutants by Using Dioxygen Activated by Resin-Exchanged Iron(II) Bipyridine under Visible Irradiation (pages 1029–1032)

      Wanhong Ma, Jing Li, Xia Tao, Ju He, Yiming Xu, Jimmy C. Yu and Jincai Zhao

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390264

      Excellent response to visible light is shown by the [FeII(bpy)3]–amberlite photocatalyst, which can effectively activate molecular oxygen in such a way as to put us one giant step nearer to our goal—the development of the ultimate green technology for decontamination [Eq. (1)].

      • equation image
    17. A Highly Enantioselective Catalyst for the Asymmetric Nozaki–Hiyama–Kishi Reaction of Allylic and Vinylic Halides (pages 1032–1035)

      Albrecht Berkessel, Dirk Menche, Christoph A. Sklorz, Michael Schröder and Ian Paterson

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390265

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      Catalytic asymmetric addition of vinylic halides and triflates to aldehydes, with useful levels of stereoinduction, has been achieved for the first time using the salen-type ligand (S,S)-5 (see scheme; PMB=para-methoxybenzyl), which contains the novel endo,endo-2,5-diamino norbornane building block. This asymmetric Nozaki–Hiyama–Kishi reaction leads to the coupling of various halides and aldehydes with high yields and enantioselectivities (up to 92 % ee).

    18. A Catalytic Carbon–Phosphorus Ylide Reaction: Phosphane-Catalyzed Annulation of Allylic Compounds with Electron-Deficient Alkenes (pages 1035–1037)

      Yishu Du, Xiyan Lu and Chunming Zhang

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390266

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      Readily available starting materials and high selectivity: These are two appealing features of the phosphane-catalyzed carbon–phosphorus ylide reaction described. Bromide, acetate, or tert-butyl carbonate derivatives of adducts formed by the Morita–Baylis–Hillman reaction react with PPh3 to form an allylic ylide. Phosphane-catalyzed annulation of the ylides with electron-deficient alkenes results in the facile construction of cyclopentenes [Eq. (1)]. X=Br, OAc, OBoc; E=CO2Et.

    19. Stabilization of Low-Oxidation-State Early Transition-Metal Complexes Bearing 1,2,4-Triphosphacyclopentadienyl Ligands: Structure of [{Sc(P3C2tBu2)2}2]; ScII or Mixed Oxidation State? (pages 1038–1041)

      Guy K. B. Clentsmith, F. Geoffrey N. Cloke, Jennifer C. Green, John Hanks, Peter B. Hitchcock and John F. Nixon

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390267

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      ScIIor mixed oxidation state ScIII/ScI? Reduction of the homoleptic ScIII complex [Sc(P3C2tBu2)3] allows access to the subvalent [{Sc(P3C2tBu2)2}2] complex (see picture), in which the metal centers are formally bivalent. DFT calculations support fomulation of the reduced species as a mixed oxidation state ScIII/ScI complex.

    20. Chiral-Mn(Salen)-Complex-Catalyzed Kinetic Resolution of Secondary Alcohols in Water (pages 1042–1044)

      Wei Sun, Hongwang Wang, Chungu Xia, Jingwei Li and Peiqing Zhao

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390268

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      A mild, green method for enantioselective kinetic resolution of secondary alcohols has been developed using Mn(salen) complexes as catalysts in water. Up to 97.8 % ee was attained. PTC=phase-transfer catalyst.

    21. Protonation of Cubane in the Gas Phase: A High-Level Ab Initio and DFT Study (pages 1044–1046)

      José-Luis M. Abboud, Ilmar A. Koppel, Juan Z. Dávalos, Peeter Burk, Ivar Koppel and Esther Quintanilla

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390269

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      The tetracyclo[4.2.0.02,4.03,8] oct-7-ylium cation is the protonation product of cubane (1) in the gas phase according to ab initio and DFT calculations. At the G2(MP2) level, the calculated gas-phase basicity of 1 is about 60 kcal mol−1 larger than that determined experimentally. The experimental thermodynamics are consistent with fast deprotonation of 2 to give cuneane (3).

    22. Synthesis and Structure of Cyclic Gold(I) Phosphanyl Complexes [{Au(PR2)}n] (pages 1046–1048)

      Diana M. Stefanescu, Holming F. Yuen, David S. Glueck, James A. Golen and Arnold L. Rheingold

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390270

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      Gold(I) Phosphanyl Complexes, such as [Au(PR2)]n, have been known for more than 25 years. However, the solid-state structure of such complexes, as well as their nature in solution, has remained somewhat of a mystery. The figure displays the cyclic and polymeric forms that are possible (L=endgroup). The structures of the complexes, and the occurrence of Au⋅⋅⋅Au interactions are discussed.

    23. Topomerization of a Distorted Diamond-Shaped Tetraborane(4) and Its Hydroboration to a closo-Pentaborane(7) with a nido Structure (pages 1049–1052)

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

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390271

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      The exchange of the short and long diagonal of the B4 diamond of 1 is the simplest variant to date of the diamond–square–diamond rearrangement, which plays a central role in the isomerization of polyhedral boranes, carboranes, and metallaboranes. Compound 2, which is readily accessible from 1, is the first derivative of pentaborane(7).

    24. The Fluoroacyltris(trifluoromethyl)borate Ion, [(CF3)3BC(O)F], a Fluoroacylboron Complex (pages 1052–1055)

      Maik Finze, Eduard Bernhardt, Helge Willner and Christian W. Lehmann

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390272

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      Nucleophilic addition of fluoride ions at the carbonyl carbon atom in (CF3)3BCO in liquid sulfur dioxide leads to the formation of the boron acyl fluoride ion [(CF3)3BC(O)F] (see structural formula), the first example of a compound with a BC(O)F group and an anionic acyl fluoride.

    25. A Versatile Catalyst for the Sonogashira Coupling of Aryl Chlorides (pages 1056–1058)

      Axel Köllhofer, Thomas Pullmann and Herbert Plenio

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390273

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      Aryl chlorides are suitable substrates for the Sonogashira coupling! By using the versatile catalyst system Na2[PdCl4]/PR3/CuI (PR3=(1-Ad)2PBn, PtBu3), the Sonogashira coupling [Eq. (a)] of aryl chlorides with alkynes generates excellent yields of the corresponding disubstituted aryl alkynes.

    26. Hydrogen-Bonded Sugar-Alcohol Trimers as Hexadentate Silicon Chelators in Aqueous Solution (pages 1058–1062)

      Klaus Benner, Peter Klüfers and Martin Vogt

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390274

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      Building bridges: Fumed colloidal silica can be dissolved in alkaline aqueous solutions of the open-chain sugar alcohols mannitol, xylitol, and threitol. These polyols are able to form six-coordinate silicon complexes that are stabilized by intramolecular hydrogen bonds. The prototypical core is shown (yellow bars: the intramolecular H bonds).

    27. Preview: Angew. Chem. Int. Ed. 9/2003 (page 1069)

      Article first published online: 26 FEB 2003 | DOI: 10.1002/anie.200390275

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