Angewandte Chemie International Edition

Cover image for Vol. 43 Issue 5

January 23, 2004

Volume 43, Issue 5

Pages 531–645

    1. Cover Picture: σ-Bond Stretching: A Static Approach for a Dynamic Process (Angew. Chem. Int. Ed. 5/2004) (page 531)

      David Scheschkewitz, Hideki Amii, Heinz Gornitzka, Wolfgang W. Schoeller, Didier Bourissou and Guy Bertrand

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200490004

      A motion picture of chemical transformation can be pieced together only from femtosecond spectroscopic techniques. The Communication by G. Bertrand and co-workers on page 585 ff. describes how the reaction profile corresponding to the inversion of bicyclo[1.1.0]butane, which involves the stretching of the B[BOND]B bond as symbolized by the tugging men, can be modeled by series of analogues that contain the boron–phosphorus ring.

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      Synthesis and Biological Evaluation of an Indomethacin Library Reveals a New Class of Angiogenesis-Related Kinase Inhibitors (page 540)

      Claudia Rosenbaum, Patrick Baumhof, Ralf Mazitschek, Oliver Müller, Athanassios Giannis and Herbert Waldmann

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200490006

    3. Web Site: The Living Cell (page 542)

      Georg Pohnert

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200490007

    4. Trigonal Prismatic or not Trigonal Prismatic? On the Mechanisms of Oxygen-Atom Transfer in Molybdopterin-Based Enzymes (pages 546–549)

      Martin Kaupp

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200301690

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      Nature is versatile and can make use of even seemingly exotic bonding situations. Recent quantum chemical evidence suggests trigonal-prismatic intermediates and transition states occur in oxygen-atom transfer catalysis of molybdopterin-based enzymes from the DMSO reductase family (see structure, green C, yellow S, blue N, red O, white H). This Highlight presents the fascinating theoretical and experimental findings within the general framework of “non-VSEPR” structures of d0–d2 transition metal complexes.

    5. New Catalytic Approaches in the Stereoselective Friedel–Crafts Alkylation Reaction (pages 550–556)

      Marco Bandini, Alfonso Melloni and Achille Umani-Ronchi

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200301679

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      Still going strong after 125 years: The development of new catalytic systems for the enantioselective construction of benzylic stereocenters is a significant goal for the chemical community. Recently numerous chiral metal-based and metal-free, homogeneous and heterogeneous catalysts have been reported that control the stereochemical course of Friedel–Crafts alkylations of electron-rich aromatic systems (see scheme).

    6. Emerging Supramolecular Chemistry of Gases (pages 558–571)

      Dmitry M. Rudkevich

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200300606

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      The ins and outs of gases: A deeper understanding into the interaction of gases with biological molecules is obtained by using the principles and techniques of supramolecular chemistry (see schematic representation). This approach not only provides knowledge about the structure and dynamics of receptor–analyte complexes on a molecular level, it also allows for the synthesis of more-selective and sensitive receptors for gas sensing, storage, and controlled release.

    7. Anion Encapsulation by Neutral Supramolecular Assemblies of Cyclic CuII Complexes: A Series of Five Polymerization Isomers, [{cis-CuII(μ-OH)(μ-pz)}n], n=6, 8, 9, 12, and 14 (pages 574–577)

      Gellert Mezei, Peter Baran and Raphael G. Raptis

      Version of Record online: 29 DEC 2003 | DOI: 10.1002/anie.200352636

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      Concentric circles: The interplay of metal-coordination geometry, dipolar interactions, and hydrogen bonding orchestrate the complex supramolecular assembly of three or four neutral metallacycles of [{cis-Cu(μ-OH)(μ-pz)}n] n=6, 8, 9, 12, 14, that encapsulate anions (encapsulated SO42− depicted; Cu blue; O red; N light blue; C black; S yellow) by multiple hydrogen bonding. This orchestration of several chemical forces for the accomplishment of a specific task imitates the strategies of Nature for similar purposes.

    8. The Origin of the Magnetic Moments in Compressed Crystals of Polymeric C60 (pages 577–580)

      Jordi Ribas-Ariño and Juan J. Novoa

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352118

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      Magnetism in polymeric rhombohedral C60phases was studied by ab initio calculations. Compression of C60 leads to the formation of C60–C60 bonds in the S0 state, and with increasing pressure the S0 and T2 curves meet (see picture), and some of the bonds can cross to the magnetically active T2 state. When the pressure is released these follow the T2 curve and remain magnetically active at ambient pressure. r=interfullerene distance.

    9. Noncovalent Ligand Strands for Transition-Metal Helicates: The Straightforward and Stereoselective Self-Assembly of Dinuclear Double-Stranded Helicates Using Hydrogen Bonding (pages 581–584)

      Shane G. Telfer, Tomohiro Sato and Reiko Kuroda

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352833

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      A genuinely supramolecular approach to transition-metal helicates is presented in which eight simple components (four ions and four small molecules) self-assemble to form dinuclear double helicates, where the ligand strands are built up through hydrogen-bonding interactions (see picture). The self-assembly process was found to be highly stereoselective.

    10. σ-Bond Stretching: A Static Approach for a Dynamic Process (pages 585–587)

      David Scheschkewitz, Hideki Amii, Heinz Gornitzka, Wolfgang W. Schoeller, Didier Bourissou and Guy Bertrand

      Version of Record online: 8 JAN 2004 | DOI: 10.1002/anie.200352944

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      Ring stretching: The reaction profile corresponding to the inversion of bicyclo[1.1.0]butane derivatives, including the cyclobutane-1,3-diyl transition state, has been modeled by the preparation of a series of boron–phosphorus-containing analogues (see picture: P red; B blue). These differ only in the substituents around the B2P2 core, yet a variation of 40 % in the boron–boron separation is observed.

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      Anti-Markovnikov Hydrofunctionalization of Olefins Mediated by Rhodium–Porphyrin Complexes (pages 588–590)

      Melanie S. Sanford and John T. Groves

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200351941

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      A rationally designed mechanistic approach to anti-Markovnikov olefin hydrofunctionalization and its application to the synthesis of heterocycles are described. Porphyrin–rhodium complexes have been shown to exhibit remarkable reactivity and selectivity for each step of the proposed catalytic cycle (see scheme). A critical step of this reaction sequence is a new, facile, and remarkably general carbon–heteroatom bond-forming reductive elimination.

    12. Imines in Stille-Type Cross-Coupling Reactions: A Multicomponent Synthesis of α-Substituted Amides (pages 590–594)

      Jason L. Davis, Rajiv Dhawan and Bruce A. Arndtsen

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352123

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      An alternative to nucleophilic chemistry for the construction of α-substituted amides and amine derivatives from imines is provided by the Stille-type coupling of imines with organotin reagents and acid chlorides (see scheme). This Pd-catalyzed reaction is suitable for components with a range of functional groups and has been extended into a four-component-coupling reaction with carbon monoxide. dba=dibenzylideneacetone, RT=room temperature.

    13. How Single and Bifurcated Hydrogen Bonds Influence Proton-Migration Rate Constants, Redox, and Electronic Properties of Phenoxyl Radicals (pages 594–597)

      Fabrice Thomas, Olivier Jarjayes, Hélène Jamet, Sylvain Hamman, Eric Saint-Aman, Carole Duboc and Jean-Louis Pierre

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352368

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      Hydrogen-bonded phenoxyl radicals are made and the strength of the hydrogen bond between the O(phenoxyl) and the H(ammonium) atoms strongly affects their stability. The rate constants for the intramolecular proton-migration process in these systems are reported and a bifurcated hydrogen-bonded system has been characterized (see model). Investigations show that the proton transfer from the phenoxyl-radical cation to the tertiary amine is assisted by a neighboring nitrogen atom.

    14. Colloidal Carbon Spheres and Their Core/Shell Structures with Noble-Metal Nanoparticles (pages 597–601)

      Xiaoming Sun and Yadong Li

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352386

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      All wrapped up: Carbon-encapsulated metal nanoparticles, carbon microspheres decorated with metal nanoparticles, and particles with layered structures are all accessible by means of a method based on hydrothermal treatment of glucose, which produces monodisperse colloidal carbon microspheres with reactive surfaces. The picture shows silver-cored carbon spheres obtained by using silver nanoparticles as seeds.

    15. Automated Solid-Phase Synthesis of Protected Tumor-Associated Antigen and Blood Group Determinant Oligosaccharides (pages 602–605)

      Kerry Routenberg Love and Peter H. Seeberger

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352539

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      Speedy synthesis: The development of a novel linker and monitoring each glycosylation reaction during automated solid-phase synthesis allows the rapid assembly of three Lewis-type cell-surface oligosaccharides. The synthesis of the protected tumor-marker Ley–Lex (see structure; Bn=benzyl, Piv=pivaloyl, TCA=trichloroacetyl) from monosaccharide building blocks was achieved in just 23 h, while the syntheses of Lewis X and Lewis Y required only 12 and 14 h, respectively.

    16. The Shape of Neutral Valine (pages 605–610)

      Alberto Lesarri, Emilio J. Cocinero, Juan C. López and José L. Alonso

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352543

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      Jet-cooled rotational spectroscopy with laser ablation has enabled two conformers of neutral valine to be observed in the gas phase. The most stable conformer (I a) exhibits a bifurcated amine-to-carbonyl (NH⋅⋅⋅O[DOUBLE BOND]C) intramolecular hydrogen bond, while the second conformer (II a) presents a hydrogen bond between the lone pair of electrons on the nitrogen atom and the hydroxy group (N⋅⋅⋅O[BOND]H). The isopropyl side chain adopts a similar staggered arrangement in both conformers.

    17. Asymmetric Induction in Ruthenium-Catalyzed [2+2] Cycloadditions between Bicyclic Alkenes and a Chiral Acetylenic Acyl Sultam (pages 610–613)

      Karine Villeneuve and William Tam

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352555

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      Cyclobutene tricyclic products were isolated in good yields (44–99 %) from Ru-catalyzed [2+2] cycloadditions between bicyclic alkenes and a chiral acetylenic acyl sultam (see scheme). The cycloadditions occurred with high stereoselectivity (only exo cycloadducts were formed) and high levels of asymmetric induction (67–98.8 % ee after removal of the chiral auxiliary). X=H, CH2OMe, Br; X–X=Ar; Y=CH2, O, CHPh; Cp*=1,2,3,4,5-pentamethylcyclopentadiene; COD=1,5-cyclooctadiene.

    18. Glycosyltransferase-Catalyzed Synthesis of Thiooligosaccharides (pages 613–615)

      Jamie R. Rich, Adam Szpacenko, Monica M. Palcic and David R. Bundle

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352606

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      An alternative to chemical synthesis: thiooligosaccharides can be prepared from appropriate carbohydrate thiols and sugar nucleotide donors by incubation with glycosyltransferases. The products of these reactions are stable towards glycosylhydrolases and may serve as antigens with extended in vivo availability.

    19. A Tandem Epoxidation/Stereoselective Intramolecular [4+3] Cycloaddition Reaction Involving Nitrogen-Stabilized Oxyallyl Cations Derived from Chiral Allenamides (pages 615–618)

      Challeppan Rameshkumar and Richard P. Hsung

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352632

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      Tandem cycling: Nitrogen-stabilized chiral oxyallyl cation intermediates are generated by chemoselective epoxidation of allenamides tethered to either the α or γ carbon atom of dienes. The stereoselectivity of the subsequent [4+3] cycloaddition step of the tandem reaction shown in the scheme depends on the length of the tether and the chiral auxiliary (N*) on the allenamide. DMDO=dimethyl dioxirane, PG=protecting group.

    20. Solid-State Reshaping of Crystals: Flash Increase in Porosity of Zirconium Phosphate-Hypophosphite That Contains Polyethylenoxa Diphosphonate Pillars (pages 619–621)

      Ernesto Brunet, María José de la Mata, Olga Juanes and Juan Carlos Rodríguez-Ubis

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352711

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      Shape shifting: A novel pillared, solid organic–inorganic phase is prepared by stepwise double topotactic exchange of γ-zirconium phosphate with pentaethylenglycol-derived diphosphonic acid and hypophosphite. The interlayer distance of the title material sharply increases when treated with methylamine. This enormous sensitivity of microcrystalline porosity towards intercalation of small molecules has no precedent.

    21. Combinatorial Synthesis of Functionalized 1,3-Thiazine Libraries Using a Combined Polymer-Supported Reagent/Catch-and-Release Strategy (pages 621–624)

      Gernot A. Strohmeier and C. Oliver Kappe

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352731

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      A dual role: The supported sulfonic acid reagent promotes the ring closure of the thiazine products and also binds them in situ as ion pairs (see scheme). The nonbasic by-products and excess reagents can be removed by filtration and the products subsequently released on treatment with triethylamine (TEA).

    22. Environmental Fluctuations Facilitate Electron-Hole Transfer from Guanine to Adenine in DNA π Stacks (pages 624–627)

      Alexander A. Voityuk, Khatcharin Siriwong and Notker Rösch

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352824

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      The relative energies of radical cation states on nucleobases in DNA are considerably affected by the local distribution of water molecules and counterions. In fact, fluctuations of ΔG are large enough to render electron-hole transfer from G+ to A energetically feasible, thus allowing a changeover from the generally accepted G-hopping mechanism to A-hopping (see picture).

    23. Copper(I) Cyanide: A Simple Compound with a Complicated Structure and Surprising Room-Temperature Reactivity (pages 628–630)

      Simon J. Hibble, Sharon G. Eversfield, Andrew R. Cowley and Ann M. Chippindale

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352844

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      Making Waves: Low-temperature CuCN has a curious wave structure (see picture Cu purple, C/N blue). Interconversion of this and the high-temperature, highly disordered form can be achieved at room-temperature via a novel zeolitic intermediate which is also structurally characterized.

    24. Selenocyclizations: Control by Coordination and by the Counterion (pages 631–633)

      Shaista S. Khokhar and Thomas Wirth

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352884

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      Selective cyclizations of selenium electrophiles lead to either tetrahydrofurans or lactones (see scheme), depending on the counterions and additives. Modification of the selenium electrophiles allow selective cyclizations, irrespective of the reaction conditions applied.

    25. A Porphyrin Dye with Monoexponential Fluorescence Intensity and Anisotropy Decay Behavior in Spherical Micelles (pages 634–636)

      Josef Duschl, Martin Michl and Werner Kunz

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200351773

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      The size and the shape of micelles can be determined with a new fluorescence dye (see picture blue N, turquoise C, red O). The fluorescence lifetime of this new porphyrin derivative is about 10 ns, which is in the order of the rotation time of a micelle. The size of the dye (diameter ca. 37 Å) ensures that it perfectly fits into most micelles. It is the first fluorescent probe that reflects only the rotation of the micelles without the disturbing internal motions of the dye.

    26. Synthesis and Structure of a 1,3-Diphosphacyclobutadienediide: An Aniomesolytic Fragmentation of a 1,3-Diphosphetane-2,4-diyl in Solution (pages 637–641)

      Manuel Sebastian, Martin Nieger, Dénes Szieberth, László Nyulászi and Edgar Niecke

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200352746

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      Stepwise reduction of the 1,3-diphosphetane-2,4-diyl 1 by alkali metals (Li, K) leads to the 1,3-diphoshacyclobutadiendiide salts 2 by aniomesolytic fragmentation. DFT calculations provide insight into the reaction pathway.

    27. Preview: Angew. Chem. Int. Ed. 5/2004 (page 645)

      Version of Record online: 21 JAN 2004 | DOI: 10.1002/anie.200490008

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