Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 5

January 21, 2005

Volume 44, Issue 5

Pages 653–827

    1. Cover Picture: Highly Efficient Dynamic Kinetic Resolution of Azlactones by Urea-Based Bifunctional Organocatalysts (Angew. Chem. Int. Ed. 5/2005) (page 653)

      Albrecht Berkessel, Felix Cleemann, Santanu Mukherjee, Thomas N. Müller and Johann Lex

      Version of Record online: 18 JAN 2005 | DOI: 10.1002/anie.200590014

      Ureas have come a long way from Wöhler's preparation of urea from ammonium cyanate in 1828 to the chiral ureas that play an important role in asymmetric organocatalysis today. In their Communication on page 807 ff. Berkessel et al. report the use of bifunctional urea-based organocatalysts for the highly enantioselective dynamic kinetic resolution of azlactones. The cover picture shows the hydrogen-bonded supramolecular aggregate formed from the urea catalyst and an azlactone substrate (graphic: K. Etzenbach-Effers).

    2. Quasi-Periodic Organization in Soft Self-Assembling Matter (pages 672–673)

      Georg H. Mehl

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200461639

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      Micelles made up of dendritic molecules can form a liquid quasi-crystalline phase. The phase structure (see picture) is characterized by a 12-fold symmetry, defying the rules of classical crystallography. The phase structure is assembled from only one set of building blocks, differentiating this system from metal alloys, in which at least two different types of atoms are required.

    3. Catalysts for Cross-Coupling Reactions with Non-activated Alkyl Halides (pages 674–688)

      Anja C. Frisch and Matthias Beller

      Version of Record online: 18 JAN 2005 | DOI: 10.1002/anie.200461432

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      The trends and latest developments in metal-catalyzed cross-coupling reactions of alkyl halides are examined in an overview of this highly topical area of research. Mechanistic investigations have led to a variety of procedures for the selective cross-coupling of non-activated alkyl halides with a variety of organometallic nucleophiles under mild reaction conditions (see scheme).

    4. Dithiol Proteins as Guardians of the Intracellular Redox Milieu in Parasites: Old and New Drug Targets in Trypanosomes and Malaria-Causing Plasmodia (pages 690–715)

      R. Luise Krauth-Siegel, Holger Bauer and R. Heiner Schirmer

      Version of Record online: 18 JAN 2005 | DOI: 10.1002/anie.200300639

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      Parasitic diseases such as sleeping sickness, Chagas' disease, and malaria are widespread throughout the world, and there is an urgent need for affordable antiparasitic medication. An approach in the search for new drugs is based on the use of enzyme inhibitors that block the antioxidative pathways in the pathogens. The picture shows glutathione reductase from the malaria parasite Plasmodium falciparum.

    5. Single-Triggered Trimeric Prodrugs (pages 716–720)

      Keren Haba, Mikhail Popkov, Marina Shamis, Richard A. Lerner, Carlos F. Barbas III and Doron Shabat

      Version of Record online: 18 JAN 2005 | DOI: 10.1002/anie.200461657

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      The knock-on effect of a single catalytic reaction by a specific enzyme on a prodrug platform initiates the sequential collapse of the whole array to release the active drug units (see scheme). Such a dendritic system may provide a means to improve selective chemotherapeutic approaches in cancer therapy.

    6. Unusual Magnetic Properties of the Edge-Sharing Bioctahedral Dirhenium(IV) Complex of Pyridine-2-thiolate (pages 720–724)

      Keisuke Umakoshi, Noriko Misasa, Chikako Ohtsu, Takashi Kojima, Maxim Sokolov, Makoto Wakeshima, Yukio Hinatsu and Masayoshi Onishi

      Version of Record online: 13 DEC 2004 | DOI: 10.1002/anie.200460532

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      A thermally accessible triplet excited state: The dirhenium(IV) complex [Re2Cl2O(pyt)4] (1; Hpyt=pyridine-2-thiol) and its one-electron-reduced species were prepared and structurally characterized. Unique temperature-dependent magnetic behavior was observed for the ReIV2 species (see picture).

    7. Generation of Monodisperse Particles by Using Microfluidics: Control over Size, Shape, and Composition (pages 724–728)

      Shengqing Xu, Zhihong Nie, Minseok Seo, Patrick Lewis, Eugenia Kumacheva, Howard A. Stone, Piotr Garstecki, Douglas B. Weibel, Irina Gitlin and George M. Whitesides

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200462226

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      Small-scale engineering: A new strategy for the production of monodisperse colloid particles with precise control of their size, shape, and composition has been developed. Highly monodisperse liquid droplets are formed by using a microfluidic device. The droplets are shaped in a microchannel (spheres, disks, and rods; see images) and solidified in situ by either polymerization or thermal setting.

    8. Gas-Phase Synthesis of [Ag4H]+ and Its Mediation of the C[BOND]C Coupling of Allyl Bromide (pages 728–731)

      George N. Khairallah and Richard A. J. O'Hair

      Version of Record online: 23 DEC 2004 | DOI: 10.1002/anie.200461328

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      Collision-induced dissociation (CID) of silver–amino acid clusters results in the formation of the silver hydride cluster [Ag4H]+, which mediates C[BOND]C bond coupling of allyl bromide (see scheme). Energy-resolved CID experiments reveal that the product is 1,5-hexadiene and suggest analogies between the chemistry of the clusters and that of silver surfaces and nanoparticles.

    9. The Effect of the f–f Interaction on the Dynamic Magnetism of a Coupled 4f8 System in a Dinuclear Terbium Complex with Phthalocyanines (pages 731–733)

      Naoto Ishikawa, Satoshi Otsuka and Youkoh Kaizu

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200461546

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      The sandwich complex tris(phthalocyaninato)diterbium with a coupled 4f8 system exhibits dynamic magnetic properties, which were clarified by means of alternating current magnetic susceptibility measurements on the bis-terbium and isostructural Tb–Y complexes (see picture, R=C4H9).

    10. A Double Iodoetherification of σ-Symmetric Diene Acetals for Installing Four Stereogenic Centers in a Single Operation: Short Asymmetric Total Synthesis of Rubrenolide (pages 734–737)

      Hiromichi Fujioka, Yusuke Ohba, Hideki Hirose, Kenichi Murai and Yasuyuki Kita

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200461584

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      Tetrahydrofuran units with multiple chiral centers are formed in a highly diastereoselective manner through the one-pot double intramolecular haloetherification of σ-symmetric diene acetals (see scheme). The utility of the method was demonstrated by the short asymmetric synthesis of (+)-rubrenolide.

    11. Preparation of Nitrogen-Rich Nanolayered, Nanoclustered, and Nanodendritic Carbon Nitrides (pages 737–739)

      My Hang V. Huynh, Michael A. Hiskey, Jose G. Archuleta and Edward L. Roemer

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200461758

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      Only C and N atoms are present in the high-nitrogen compound 4,4′,6,6′-tetra(azido)azo-1,3,5-triazine (TAAT), which is thus an ideal precursor for carbon nitrides. Controlled pyrolysis of TAAT afforded novel nitrogen-rich carbon nitrides in the form of nanolayers (C2N3), nanoclusters (C3N5), and nanodendrites (C3N5, see SEM image). The pyrolyses occur at low temperature and without applied pressure and require no vacuum systems, extraction, carbonization, or purification.

    12. Nonsolvated, Aggregated 1,1-Dilithiosilane and the Derived Silyl Radicals (pages 739–743)

      Dmitry Bravo-Zhivotovskii, Ilya Ruderfer, Semyon Melamed, Mark Botoshansky, Boris Tumanskii and Yitzhak Apeloig

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200461765

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      A triplet-state silyl biradical 2 and a family of silyl radicals, in which the silyl radical center is part of a silyllithium aggregate, are generated photochemically from the gem-dilithiosilane [(R2SiLi2)(R2HSiLi)2] (1, see scheme; R′: unknown). The EPR spectrum of 2 consists of four side lines from ΔM=1 transitions and a signal at half-field resulting from the forbidden ΔM=2 transitions.

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      Catalytic Nanomotors: Remote-Controlled Autonomous Movement of Striped Metallic Nanorods (pages 744–746)

      Timothy R. Kline, Walter F. Paxton, Thomas E. Mallouk and Ayusman Sen

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200461890

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      A move in the right direction: Micrometer-sized rods with Pt/Ni/Au/Ni/Au segments move autonomously with good directionality in the presence of a magnetic field when placed in aqueous hydrogen peroxide (see picture). The propulsive force results from an interfacial tension gradient generated by the catalytic decomposition of H2O2 at the Pt end while the orientation stems from the interaction of the magnetic field with the magnetized Ni segments.

    14. Efficient Two-Photon-Sensitized Luminescence of a Europium(III) Complex (pages 747–750)

      Li-Min Fu, Xiao-Fan Wen, Xi-Cheng Ai, Yang Sun, Yi-Shi Wu, Jian-Ping Zhang and Yuan Wang

      Version of Record online: 15 DEC 2004 | DOI: 10.1002/anie.200462382

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      Red emission (λem=614 nm) from EuIII, sensitized by two-photon absorption, has been demonstrated for the europium(III) complex [Eu(tta)3dpbt] (1). A large two-photon-absorption cross section and a high luminescence efficiency of the europium complex ensure a high efficiency of two-photon sensitization.

    15. Self-Assembly and Electrical Conductivity Transitions in Conjugated Oligoaniline–Surfactant Complexes (pages 751–756)

      Zhixiang Wei, Teija Laitinen, Bernd Smarsly, Olli Ikkala and Charl F. J. Faul

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200460928

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      Functional and externally controllable electroactive nanostructures are obtained by an ionic self-assembly process. 2D rectangular columnar structures (see picture) comprising oligoanilines were prepared by complexation with double-tail phosphate surfactants. Upon heating, tetraaniline complexes show an order–disorder transition from this 2D phase structure to a disordered state as a reversible change in the electrical conductivity.

    16. Biomimetic Total Synthesis of Gambogin and Rate Acceleration of Pericyclic Reactions in Aqueous Media (pages 756–761)

      K. C. Nicolaou, Hao Xu and Markus Wartmann

      Version of Record online: 18 JAN 2005 | DOI: 10.1002/anie.200462211

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      A significant rate acceleration of a Claisen rearrangement and of a Claisen/Diels–Alder reaction cascade sequence was observed in the presence of water. This reaction sequence was used in a total synthesis of gambogin (1) from a tricyclic dialkene 3 via 2.

    17. A Novel Dinuclear Chiral Niobium Complex for Lewis Acid Catalyzed Enantioselective Reactions: Design of a Tridentate Ligand and Elucidation of the Catalyst Structure (pages 761–764)

      Shū Kobayashi, Kenzo Arai, Haruka Shimizu, Yoichi Ihori, Haruro Ishitani and Yasuhiro Yamashita

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200462204

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      Two's company: By using a novel chiral ligand a dinuclear chiral niobium catalyst for highly enantioselective Mannich-type reactions was developed. Tridentate binol derivatives provide excellent asymmetric environments around the niobium atom, and the Mannich-type reactions proceeded smoothly in high yields with high enantioselectivities (see scheme; NMI=N-methylimidazole).

    18. Spirocycloisomerization of Tethered Alkylidene Glycocyamidines: Synthesis of a Base Template Common to the Palau'amine Family of Alkaloids (pages 765–769)

      Hugo Garrido-Hernandez, Masakazu Nakadai, Marc Vimolratana, Qingyi Li, Thomas Doundoulakis and Patrick G. Harran

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200462069

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      The facile spirocyclization of tethered bisalkylidene 1 suggests a general synthetic strategy for preparing alkaloids of the palau'amine family. The development and characteristics of this core model system are discussed.

    19. Dibariumplatinide: (Ba2+)2Pt2−⋅2 e and Its Relation to the Alkaline-Earth-Metal Subnitrides (pages 770–773)

      Andrey Karpov, Ulrich Wedig, Robert E. Dinnebier and Martin Jansen

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200462055

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      Solitary confinement: Ba2Pt (see structure) which contains isolated platinide ions (Pt2−) was synthesized from the elements, sealed in tantalum ampoules, at 1223 K in argon. In contrast to the related Cs2Pt, the Ba compound contains excess electrons, which are responsible for its metallic behavior. The presence of isolated Pt2− ions was confirmed by high resolution X-ray diffraction and by theoretical calculations.

    20. Field-Induced Switching of Chirality in Undulated Ferroelectric and Antiferroelectric SmCP Phases Formed by Bent-Core Mesogens (pages 774–778)

      Ramaiahgari Amaranatha Reddy, Martin W. Schröder, Michael Bodyagin, Horst Kresse, Siegmar Diele, Gerhard Pelzl and Wolfgang Weissflog

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200461490

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      Switching signs: The polar structure of a tilted smectic C phase formed by a homologous series of bent-core mesogens changes from antiferroelectric to ferroelectric with increasing chain length. The polar switching of the banana-shaped molecules occurs by collective rotation around their long molecular axes (a) or by rotation of the director around the tilt cone (b). Red and blue designate layers of opposite chirality.

    21. Preferential Oxidation of CO in H2 by Aqueous Polyoxometalates over Metal Catalysts (pages 778–782)

      Won Bae Kim, Tobias Voitl, Gabriel J. Rodriguez-Rivera, Steven T. Evans and James. A. Dumesic

      Version of Record online: 23 DEC 2004 | DOI: 10.1002/anie.200461601

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      Stream cleaning: CO in CO/H2 mixtures is oxidized preferentially at room temperature with an aqueous polyoxometalate (POM) solution over gold catalysts (see scheme). The rate of H2 oxidation is slow and is inhibited by CO. This process can be used to remove CO efficiently from H2 gas streams. The solution containing protons and reduced POM can be used to produce electrical energy at a fuel-cell anode through re-oxidation of the reduced POM.

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      Hydrophobic and Ultrahydrophobic Multilayer Thin Films from Perfluorinated Polyelectrolytes (pages 782–785)

      Rana M. Jisr, Hassan H. Rmaile and Joseph B. Schlenoff

      Version of Record online: 23 DEC 2004 | DOI: 10.1002/anie.200461645

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      Making contact: The hydrophobicity of the top layer of a multilayer thin film composed of polyelectrolytes and clay nanorods determines the contact angle of a water drop on the surface (see picture). The film is built up layer-by-layer on a silicon surface, thus enabling the surface properties to be readily modified by changing the polyelectrolyte used.

    23. The First Trimetallic Pd/Tl/Co Carbonyl Cluster, Trigonal [Pd93-TlCo(CO)3L}(μ2-CO)63-CO)3L6]: Ligand-Stabilization of the Trigonal-Bipyramidal [TlCo(CO)3L] Entity (pages 786–790)

      Evgueni G. Mednikov, Charles G. Fry and Lawrence F. Dahl

      Version of Record online: 23 DEC 2004 | DOI: 10.1002/anie.200461124

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      Easy come, easy go: The reaction of [Pd4(CO)5L4] and/or [Pd10(CO)12L6] (L=PEt3) with [TlCo(CO)4] gives the title compound (see structure, CO and ethyl groups removed), in which the [TlCo(CO)4] reactant serves as a ligand (in its monosubstituted [TlCo(CO)3L] form). Temperature-dependent NMR spectroscopy indicates dynamic behavior involving the rapid reversible dissociation/association of the entire [TlCo(CO)3L] ligand.

    24. Polymer-Induced Self-Assembly of Alkynylplatinum(II) Terpyridyl Complexes by Metal⋅⋅⋅Metal/π⋅⋅⋅π Interactions (pages 791–794)

      Cong Yu, Keith Man-Chung Wong, Kenneth Hoi-Yiu Chan and Vivian Wing-Wah Yam

      Version of Record online: 23 DEC 2004 | DOI: 10.1002/anie.200461261

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      Deprotonation of polycarboxylic acids induces the self-assembly of terpyridylplatinum(II) complexes (see picture) and triggers remarkable changes in the UV/Vis spectra and emission intensities. The changes in the electronic spectra arise from metal-metal-to-ligand charge transfer transitions resulting from the aggregation of the complexes.

    25. Enantioselective Organocatalyzed α Sulfenylation of Aldehydes (pages 794–797)

      Mauro Marigo, Tobias C. Wabnitz, Doris Fielenbach and Karl Anker Jørgensen

      Version of Record online: 18 JAN 2005 | DOI: 10.1002/anie.200462101

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      The facile elaboration of optically active α-sulfanyl-substituted aldehydes makes their direct preparation from unmodified aldehydes and 1-benzylsulfanyl-1,2,4-triazole particularly valuable. The substituted aldehydes are formed with excellent enantioselectivities in the presence of sterically demanding chiral pyrrolidine derivatives as organocatalysts (see scheme). R, R′=H, alkyl, allyl, benzyl, Ph.

    26. A Self-Ordered, Crystalline–Glass, Mesoporous Nanocomposite for Use as a Lithium-Based Storage Device with Both High Power and High Energy Densities (pages 797–802)

      Haoshen Zhou, Donglin Li, Mitsuhiro Hibino and Itaru Honma

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200460937

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      Current technology: A lithium-based storage device with both high power and high energy densities is formed by a nanocomposite composed of a framework of three-dimensional glass networks with uniform channels. The channels are filled by electrolyte solution and act as a lithium-ion path and the framework contains an electronic conductive oxide and therefore act as an electronic path (see picture).

    27. The Deposition of Metallopeptide-Based Coordination Polymers on Graphite Substrates: Effects of Side-Chain Functional Groups and Local Surface Structure (pages 803–806)

      Slobodan Novokmet, Mohammad S. Alam, Viatcheslav Dremov, Frank W. Heinemann, Paul Müller and Ralf Alsfasser

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461274

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      The surface dictates: The metallodipeptide complex [{Zn(Dpg-Tyr-O)}n]n+ (Dpg=dipicolylglycyl, Tyr=tyrosine) is a right-handed homochiral helical coordination polymer. Depending on the local structure of a pyrolytic graphite surface, it aggregates to form double-helical plaits (left) or two-dimensional assemblies of linearly stretched strands (right). The strands represent the first step in the formation of a three-dimensional crystal.

    28. Highly Efficient Dynamic Kinetic Resolution of Azlactones by Urea-Based Bifunctional Organocatalysts (pages 807–811)

      Albrecht Berkessel, Felix Cleemann, Santanu Mukherjee, Thomas N. Müller and Johann Lex

      Version of Record online: 18 JAN 2005 | DOI: 10.1002/anie.200461442

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      Novel tasks for a venerable molecule: Bifunctional organocatalysts of the type shown, with a quasi Lewis acidic urea or thiourea unit and a Brønsted basic amine functionality, effect the dynamic kinetic resolution of azlactones with high enantioselectivity. N-Benzoyl amino acid esters were obtained with up to 91 % ee in high yields from racemic azlactones.

    29. Calculation of Clathrate-Like Water Clusters Including H2O-Buckminsterfullerene (pages 811–815)

      Ralf Ludwig and Andreas Appelhagen

      Version of Record online: 23 DEC 2004 | DOI: 10.1002/anie.200460899

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      A true minimum structure, the buckminsterfullerene of water, (H2O)60, was studied by ab initio and density functional calculations of a total of seven water clusters. The water buckyball can be stabilized further by contact with large hydrophobic molecules such as the famous carbon analogue C60 (see picture).

    30. Very Stable and Highly Regioselective Supported Ionic-Liquid-Phase (SILP) Catalysis: Continuous-Flow Fixed-Bed Hydroformylation of Propene (pages 815–819)

      Anders Riisager, Rasmus Fehrmann, Stephan Flicker, Roy van Hal, Marco Haumann and Peter Wasserscheid

      Version of Record online: 21 DEC 2004 | DOI: 10.1002/anie.200461534

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      The advantages of heterogeneous catalysis and transition-metal catalysis in ionic liquids are combined in rhodium bisphosphine catalysts in an ionic-liquid phase on a silica support. These active, regioselective, and highly stable catalysts were applied in a fixed-bed reactor for the continuous-flow gas-phase hydroformylation of propene.

    31. Enantioselective Total Synthesis of Cylindramide (pages 820–822)

      Nicolai Cramer, Sabine Laschat, Angelika Baro, Harald Schwalbe and Christian Richter

      Version of Record online: 28 DEC 2004 | DOI: 10.1002/anie.200461823

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      Key steps in the convergent enantioselective synthesis of the cytotoxic natural product (see structural formula) are tandem Michael addition/electrophilic trapping reactions, Sonogashira coupling, Julia–Kocienski olefination, and macrocyclization. Formation of the tetramic acid completed the synthesis.

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      Preview: Angew. Chem. Int. Ed. 5/2005 (page 827)

      Version of Record online: 18 JAN 2005 | DOI: 10.1002/anie.200590016