Angewandte Chemie International Edition

Cover image for Vol. 46 Issue 10

February 26, 2007

Volume 46, Issue 10

Pages 1545–1747

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlight
    9. Minireview
    10. Review
    11. Communications
    12. Preview
    1. Cover Picture: Asymmetric Organocatalytic Domino Reactions (Angew. Chem. Int. Ed. 10/2007) (page 1545)

      Dieter Enders, Christoph Grondal and Matthias R. M. Hüttl

      Version of Record online: 22 FEB 2007 | DOI: 10.1002/anie.200790031

      A gentle nudge is all it takes to set off a line of dominoes, and the same principle applies to domino reactions with a suitable catalyst as initiator. Just as dominoes fall down sequentially, the intermediate compounds in a domino reaction react successively under the same reaction conditions to give the desired product. Thus, complex structures can often be constructed from simple precursors, as D. Enders et al. describe in their Minireview on page 1570 ff. on asymmetric organocatalytic domino reactions.

  2. Inside Cover

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlight
    9. Minireview
    10. Review
    11. Communications
    12. Preview
    1. Inside Cover: Layer-by-Layer Constructed Macroporous Architectures (Angew. Chem. Int. Ed. 10/2007) (page 1546)

      Yujie Ma, Wen-Fei Dong, Mark A. Hempenius, Helmuth Möhwald and G. Julius Vancso

      Version of Record online: 19 FEB 2007 | DOI: 10.1002/anie.200790032

      Colloidal particles of manganese carbonate covered with multilayers of high-molar-mass double-stranded DNA and cationic poly(ferrocenylsilane) (PFS) polyelectrolytes (SEM image shown) are described in the Communication by W.-F. Dong, G. J. Vancso, et al. on page 1702 ff. The macroporous structures, confirmed also by AFM (inset image), were constructed by simple sequential supramolecular assembly controlled by the persistence-length mismatch of the constituents. Upon MnCO3 core removal porous capsules were obtained.

  3. Graphical Abstract

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlight
    9. Minireview
    10. Review
    11. Communications
    12. Preview
  4. Corrigendum

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlight
    9. Minireview
    10. Review
    11. Communications
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      Multifunctional Iridium Complexes Based on Carbazole Modules as Highly Efficient Electrophosphors (page 1558)

      Wai-Yeung Wong, Cheuk-Lam Ho, Zhi-Qiang Gao, Bao-Xiu Mi, Chin-Hsin Chen, Kok-Wai Cheah and Zhenyang Lin

      Version of Record online: 19 FEB 2007 | DOI: 10.1002/anie.200790034

      This article corrects:

      Multifunctional Iridium Complexes Based on Carbazole Modules as Highly Efficient Electrophosphors1

      Vol. 45, Issue 46, 7800–7803, Version of Record online: 24 OCT 2006

  5. News

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlight
    9. Minireview
    10. Review
    11. Communications
    12. Preview
  6. Book Reviews

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlight
    9. Minireview
    10. Review
    11. Communications
    12. Preview
  7. Highlight

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlight
    9. Minireview
    10. Review
    11. Communications
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    1. Block Copolymers with Functional Inorganic Blocks: Living Addition Polymerization of Inorganic Monomers (pages 1565–1568)

      Ian Manners

      Version of Record online: 9 FEB 2007 | DOI: 10.1002/anie.200604503

      Thumbnail image of graphical abstract

      Doesn't have to be strictly organic to live: Living polymerizations of inorganic monomers provide a route to block copolymers that self-assemble in thin films or selective solvents to form functional nanodomains containing inorganic elements. An exciting addition to this field involves the recently reported living anionic addition polymerization of phosphaalkenes (see scheme; Mes=2,4,6-Me3C6H2).

  8. Minireview

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlight
    9. Minireview
    10. Review
    11. Communications
    12. Preview
    1. Asymmetric Organocatalytic Domino Reactions (pages 1570–1581)

      Dieter Enders, Christoph Grondal and Matthias R. M. Hüttl

      Version of Record online: 16 JAN 2007 | DOI: 10.1002/anie.200603129

      Thumbnail image of graphical abstract

      Domino rally: Organocatalytic domino reactions are characterized by the efficient and stereoselective construction of complex molecules from simple precursors in a single process (see scheme; TMS=trimethylsilyl). This strategy circumvents the common drawbacks of classical synthesis, such as costly protecting-group strategies and lengthy purification procedures after each synthetic step.

  9. Review

    1. Top of page
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    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlight
    9. Minireview
    10. Review
    11. Communications
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    1. Scanning Electrochemical Microscopy for Direct Imaging of Reaction Rates (pages 1584–1617)

      Gunther Wittstock, Malte Burchardt, Sascha E. Pust, Yan Shen and Chuan Zhao

      Version of Record online: 7 FEB 2007 | DOI: 10.1002/anie.200602750

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      Scanning the horizon: Scanning electrochemical microscopy has become an indispensible tool for the investigation of localized processes at interfaces. The basics of this method will be detailed along with applications and perspectives in the areas of corrosion, surface technology, membrane processes, (bio)catalysis, as well as in biological and biochemical assays.

  10. Communications

    1. Top of page
    2. Cover Picture
    3. Inside Cover
    4. Graphical Abstract
    5. Corrigendum
    6. News
    7. Book Reviews
    8. Highlight
    9. Minireview
    10. Review
    11. Communications
    12. Preview
    1. THF Solvates of Extremely Soluble Bis(2,4,6-trimethylphenyl)calcium and Tris(2,6-dimethoxyphenyl)dicalcium Iodide (pages 1618–1623)

      Reinald Fischer, Martin Gärtner, Helmar Görls, Lian Yu, Markus Reiher and Matthias Westerhausen

      Version of Record online: 30 JAN 2007 | DOI: 10.1002/anie.200604436

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      United for better solubility: A diaryl calcium compound could be isolated for the first time by fractionated crystallization of mesitylcalcium iodide. The aryl calcium iodide and diaryl calcium compounds show an extremely high solubility in THF even at −90 °C. Quantum chemical calculations point to dimerization or tetramerization through a novel η6 coordination as a possible explanation (see picture; C mauve, H white, Ca orange, I purple).

    2. Overcoming Thermodynamic and Kinetic Limitations of Aldolase-Catalyzed Reactions by Applying Multienzymatic Dynamic Kinetic Asymmetric Transformations (pages 1624–1626)

      Johannes Steinreiber, Martin Schürmann, Michael Wolberg, Friso van Assema, Christoph Reisinger, Kateryna Fesko, Daniel Mink and Herfried Griengl

      Version of Record online: 24 JAN 2007 | DOI: 10.1002/anie.200604142

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      Dynamic and successful: The asymmetric synthesis of 2-amino-1-phenylethanol was achieved by aminomethylation of benzaldehyde in the presence of the two enzymes L-threonine aldolase and L-tyrosine decarboxylase in a novel one-pot, two-enzyme process (see scheme). A modified method with three enzymes led to the enantioenriched amino alcohol in very high yield.

    3. Domino N[BOND]H/C[BOND]H Bond Activation: Palladium-Catalyzed Synthesis of Annulated Heterocycles Using Dichloro(hetero)arenes (pages 1627–1629)

      Lutz Ackermann and Andreas Althammer

      Version of Record online: 19 JAN 2007 | DOI: 10.1002/anie.200603833

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      One after the other: A novel palladium-catalyzed domino reaction consisting of an amination and a direct C[BOND]H bond arylation allows for a general synthesis of annulated heterocycles starting from readily available 1,2-dichloroarenes and primary as well as secondary anilines (see scheme; Cy=cyclohexyl). This is highlighted by an efficient synthesis of the natural product murrayafoline A.

    4. Selective Dimetalation of [Mn(η5-C5H5)(η6-C6H6)]: Crystal Structure and Conversion to Strained [n]Metalloarenophanes (pages 1630–1633)

      Holger Braunschweig, Thomas Kupfer and Krzysztof Radacki

      Version of Record online: 18 JAN 2007 | DOI: 10.1002/anie.200604391

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      The heteroleptic sandwich complex [Mn(η5-C5H5)(η6-C6H6)] was selectively dilithiated with BuLi/pmdta to afford the highly reactive derivative [Mn(η5-C5H4Li)(η6-C6H5Li)]⋅pmdta, which was structurally characterized by X-ray diffraction (pmdta=pentamethyldiethylenetriamine). Reactions with element dihalides yielded the corresponding [2]borametalloarenophane and [1]silametalloarenophane in good yields (see scheme).

    5. Oxidative Cleavage of 3-Alkoxy-2,5-dihydrofurans and its Application to the De Novo Synthesis of Rare Monosaccharides as Exemplified by L-Cymarose (pages 1634–1637)

      Malte Brasholz and Hans-Ulrich Reissig

      Version of Record online: 12 JAN 2007 | DOI: 10.1002/anie.200604078

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      Donor-substituted α,β-unsaturated γ-keto aldehydes can be formed by the selective oxidative cleavage of 3-alkoxy-2,5-dihydrofurans. These 1,4-dicarbonyl compounds are highly suitable building blocks for the synthesis of rare sugars, for example, the dideoxypyranose L-cymarose (see scheme).

    6. [Au3Ge18]5−—A Gold–Germanium Cluster with Remarkable Au–Au Interactions (pages 1638–1640)

      Annette Spiekermann, Stephan D. Hoffmann, Florian Kraus and Thomas F. Fässler

      Version of Record online: 18 JAN 2007 | DOI: 10.1002/anie.200602003

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      Gold linkers: The first soluble gold–germanium cluster was obtained from the reaction of [Au(PPh3)Cl] and K4Ge9. The formation of the gold complex [Ge9Au3Ge9]5− (see picture) shows also an exciting result for gold chemistry: linearly coordinated gold atoms and the characteristics of aurophilic contacts between the metal atoms can be observed in the presence of polyanionic Zintl ions.

    7. Pronounced Ligand Effects and the Role of Formal Oxidation States in the Nickel-Mediated Thermal Activation of Methane (pages 1641–1644)

      Maria Schlangen, Detlef Schröder and Helmut Schwarz

      Version of Record online: 30 JAN 2007 | DOI: 10.1002/anie.200603266

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      Related but different: The thermal activation of methane by cationic nickel complexes depends crucially on the nature of ligands and the formal oxidation state of the metal, as is illustrated by the isomeric water complexes: whereas [Ni(H2O)]+ is unreactive, the NiIII isomer [Ni(H)(OH)]+ activates the C[BOND]H bond in methane.

    8. Estimation of the Kinetic Acidity from Substrate Conformation—Stereochemical Course of the Deprotonation of Cyclohexenyl Carbamates (pages 1645–1649)

      Jochen Becker, Stefan Grimme, Roland Fröhlich and Dieter Hoppe

      Version of Record online: 19 JAN 2007 | DOI: 10.1002/anie.200603347

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      Get the bends: The kinetic C[BOND]H acidity of cyclohex-2-enyl carbamates is dependent on the torsion angle between the α C[BOND]H bond and the π system of the adjacent double bond. A deprotonation study and DFT calculations of the activation energies for lithiation show that the ease of deprotonation is predictable from a conformational analysis of the substrates. Furthermore, the stereochemical course of substitution reactions was determined.

    9. Small but Effective: Copper Hydride Catalyzed Synthesis of α-Hydroxyallenes (pages 1650–1653)

      Carl Deutsch, Bruce H. Lipshutz and Norbert Krause

      Version of Record online: 15 JAN 2007 | DOI: 10.1002/anie.200603739

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      Mild and efficient: The copper hydride catalyzed diastereoselective SN2′ reduction of propargyl oxiranes provides α-hydroxyallenes bearing various functional groups (ethers, esters, alcohols; see scheme, PMHS=polymethylhydridosiloxane). The best results were obtained with a copper hydride catalyst and an N-heterocyclic carbene ligand. The resulting allenes are useful substrates, as they undergo, for example, regio- and chemoselective cycloisomerization to give 2,5-dihydrofurans.

    10. A Network of Coiled-Coil Associations Derived from Synthetic GCN4 Leucine-Zipper Arrays (pages 1654–1657)

      Michael Portwich, Sandro Keller, Holger M. Strauss, Carsten C. Mahrenholz, Ines Kretzschmar, Achim Kramer and Rudolf Volkmer

      Version of Record online: 9 JAN 2007 | DOI: 10.1002/anie.200603246

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      Two is better than one: Coiled-coil sequence motifs are versatile protein–protein interaction modules. Single and double substitutions of the GCN4 coiled coil (1, 2, and 3) showed that the core positions a and d in the third heptad act as a switch for the transition from the native homodimeric to homotrimeric structures. This creates a synthetic three-membered association network with monomeric, homotrimeric, and heterodimeric coiled-coil states.

    11. A Metalloid [Ga23{N(SiMe3)2}11] Cluster: The Jellium Model Put to Test (pages 1658–1662)

      Jens Hartig, Anna Stößer, Petra Hauser and Hansgeorg Schnöckel

      Version of Record online: 18 JAN 2007 | DOI: 10.1002/anie.200604311

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      Not a bird, not a plane, perhaps a superatom: The term “superatom” has been used for “naked” metal atom clusters with a certain electronic structure. On the basis of structural data the question of whether this classification—the Jellium model—is a suitable description of a metalloid cluster with the same number of valence electrons is addressed. The picture shows the superatomic core of naked and ligand-bearing Ga atoms in the title cluster.

    12. Is Eka-Mercury (Element 112) a Group 12 Metal? (pages 1663–1666)

      Nicola Gaston, Ingo Opahle, Heinz W. Gäggeler and Peter Schwerdtfeger

      Version of Record online: 26 JAN 2007 | DOI: 10.1002/anie.200604262

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      Super heavy: According to relativistic Dirac–Kohn–Sham calculations, eka-mercury (element 112) is a semiconductor in the solid state (see band structure; red: filled bands, blue: empty bands). In the absence of relativistic effects, condensed eka-mercury would be a hexagonal close-packed metal similar to zinc and cadmium.

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      Convergent Chemical Synthesis and Crystal Structure of a 203 Amino Acid “Covalent Dimer” HIV-1 Protease Enzyme Molecule (pages 1667–1670)

      Vladimir Yu. Torbeev and Stephen B. H. Kent

      Version of Record online: 24 JAN 2007 | DOI: 10.1002/anie.200604087

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      Synthesizing enzymes: The great potential of recently developed methods for the fully convergent chemical synthesis of proteins has been demonstrated by the synthesis of the 203 amino acid “covalent dimer” HIV-1 protease (see picture). The 21 870 Da protein synthesized has full enzymatic activity and the correct three-dimensional structure, as demonstrated by high-resolution X-ray crystallographic analysis.

    14. Luminescence Detection of Open-Shell Transition-Metal Ions by Photoinduced Electron Transfer Controlled by Internal Charge Transfer of a Receptor (pages 1671–1674)

      Thomas Schwarze, Holger Müller, Carsten Dosche, Tillmann Klamroth, Wulfhard Mickler, Alexandra Kelling, Hans-Gerd Löhmannsröben, Peter Saalfrank and Hans-Jürgen Holdt

      Version of Record online: 17 JAN 2007 | DOI: 10.1002/anie.200603992

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      When push comes to shove: The oxidative photoinduced electron transfer (PET) in anthrylmethylthiomaleonitrile derivatives is regulated by the intramolecular charge transfer (ICT) of the “push–pull” dithiomaleonitrile receptor. Selective complexation with palladium chloride switches off the ICT, stops the PET, and results in fluorescence enhancement (see picture).

    15. A Simple Approach for the Selective and Sensitive Colorimetric Detection of Anionic Surfactants in Water (pages 1675–1678)

      Carmen Coll, Ramón Martínez-Máñez, M. Dolores Marcos, Félix Sancenón and Juan Soto

      Version of Record online: 22 JAN 2007 | DOI: 10.1002/anie.200603800

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      Good color sense: A sensing material (S1) containing imidazolium-anchored binding groups is used with a suitable dye (methylene blue) in a simple two-step protocol for the colorimetric detection of anionic surfactants in water (see picture). A detection limit of 1 ppm can be achieved, and the method is free from the use of hazardous solvents.

    16. Functionalized 3D Oligothiophene Dendrons and Dendrimers— Novel Macromolecules for Organic Electronics (pages 1679–1683)

      Chang-Qi Ma, Elena Mena-Osteritz, Tony Debaerdemaeker, Martijn M. Wienk, René A. J. Janssen and Peter Bäuerle

      Version of Record online: 15 JAN 2007 | DOI: 10.1002/anie.200602653

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      Family tree: Novel functionalized dendritic oligothiophenes up to a fourth generation have been prepared. The highly soluble and structurally defined macromolecules show promising optoelectronic properties and performance in organic photovoltaic devices.

    17. Chemiluminescent Energy-Transfer Cassettes Based on Fluorescein and Nile Red (pages 1684–1687)

      Junyan Han, Jiney Jose, Erwen Mei and Kevin Burgess

      Version of Record online: 19 JAN 2007 | DOI: 10.1002/anie.200603307

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      The long and the short of it: Luminol chemiluminesces with a beautiful blue color; however, to be useful for biotechnological applications, the emission must be shifted to much longer wavelengths. Energy-transfer cassettes like that shown in the picture provide one solution.

    18. A Thermally Adjustable Multicolor Photochromic Hydrogel (pages 1688–1692)

      Kazuki Matsubara, Masayoshi Watanabe and Yukikazu Takeoka

      Version of Record online: 19 JAN 2007 | DOI: 10.1002/anie.200603554

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      A rainbow of possibilities: A porous polymer gel undergoes light-triggered rapid two-state switching between two arbitrary structural colors at a controlled temperature (see picture; “on”: upon UV irradiation, “off”: in the dark). This switching is attributed to a change between two volume states. As the temperature also contributes to the degree of swelling of the gel, the color of the gel can be tuned thermally over a wide range of wavelengths.

    19. Formation of Vesicular Structures through the Self-Assembly of a Flexible Bis-Zwitterion in Dimethyl Sulfoxide (pages 1693–1697)

      Carsten Schmuck, Thomas Rehm, Katja Klein and Franziska Gröhn

      Version of Record online: 17 JAN 2007 | DOI: 10.1002/anie.200603629

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      Small molecule, large structures: The connection of two zwitterionic binding motifs with a lipophilic alkyl linker results in an amphiphilic bis-zwitterion, which forms self-assembled vesicles even in polar solutions. The data suggest that two bis-zwitterions dimerize and then further aggregate to form vesicles, most likely driven by H-bonding and van der Waals interactions between the linkers.

    20. Improving Solid-Supported Catalyst Productivity by Using Simplified Packed-Bed Microreactors (pages 1698–1701)

      Andrew R. Bogdan, Brian P. Mason, Kevin T. Sylvester and D. Tyler McQuade

      Version of Record online: 19 JAN 2007 | DOI: 10.1002/anie.200603854

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      Going with the flow: Packed-bed microreactors are formed from polymeric tubing and a resin-supported catalyst. By using supported catalysts in flow systems, productivity and recycling are greatly improved. This approach can be used to couple multiple catalysts together for generating complex molecules in one flow-through process.

    21. Layer-by-Layer Constructed Macroporous Architectures (pages 1702–1705)

      Yujie Ma, Wen-Fei Dong, Mark A. Hempenius, Helmuth Möhwald and G. Julius Vancso

      Version of Record online: 25 JAN 2007 | DOI: 10.1002/anie.200604143

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      Bottoms up! Films were built up in a layer-by-layer fashion using high-molar-mass double-stranded DNA and cationic poly(ferrocenylsilane) polyelectrolytes. In this one-step “bottom-up” self-assembly approach, a unique macroporous architecture (see picture) featuring biocompatible and redox-active components was obtained.

    22. Space- and Time-Resolved Visualization of Acid Catalysis in ZSM-5 Crystals by Fluorescence Microscopy (pages 1706–1709)

      Maarten B. J. Roeffaers, Bert F. Sels, Hiroshi Uji-i, Bart Blanpain, Pieter L'hoëst, Pierre A. Jacobs, Frans C. De Schryver, Johan Hofkens and Dirk E. De Vos

      Version of Record online: 23 JAN 2007 | DOI: 10.1002/anie.200604336

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      ZSM-5 at work: Acid-catalyzed condensation of furfuryl alcohol in the pores of zeolite ZSM-5 was followed under the fluorescence microscope. During the lifetime of a catalyst, from the reaction start to deactivation, the reactivity of the different crystal segments varies. The technique allows the heterogeneity of activity within individual crystals to be visualized (see picture).

    23. Remarkably Simple Fabrication of Superhydrophobic Surfaces Using Electroless Galvanic Deposition (pages 1710–1712)

      Iain A. Larmour, Steven E. J. Bell and Graham C. Saunders

      Version of Record online: 17 JAN 2007 | DOI: 10.1002/anie.200604596

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      Superhydrophobic surfaces with contact angles between 173° and 180° can be produced simply by spontaneous deposition of a textured gold or silver coating layer, followed by a self-assembled monolayer of polyfluoroalkyl thiol. Objects of any size or shape may be coated. For example, the metal “pond skater” (photo) stands on superhydrophobic copper legs.

    24. Anisotropically Phase-Segregated Pd–Co–Pd Sulfide Nanoparticles Formed by Fusing Two Co–Pd Sulfide Nanoparticles (pages 1713–1715)

      Toshiharu Teranishi, Masaki Saruyama, Masafumi Nakaya and Masayuki Kanehara

      Version of Record online: 24 JAN 2007 | DOI: 10.1002/anie.200603865

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      As nutty as a fruitcake! PdSx seed-mediated growth has led to the formation of heterostructured Pd–Co–Pd sulfide peanut-shaped nanoparticles, which were generated by fusing two Co–Pd sulfide acorn-shaped nanoparticles with the Co9S8 phases aligned in the same crystallographic orientation (see TEM image).

    25. Combating Alzheimer's Disease With Multifunctional Molecules Designed for Metal Passivation (pages 1716–1718)

      Harvey Schugar, David E. Green, Meryn L. Bowen, Lauren E. Scott, Tim Storr, Karin Böhmerle, Fancy Thomas, David D. Allen, Paul R. Lockman, Michael Merkel, Katherine H. Thompson and Chris Orvig

      Version of Record online: 25 JAN 2007 | DOI: 10.1002/anie.200603866

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      A trifunctional approach: 3-hydroxy-4-pyridinones that contain phenol groups for antioxidant functionality are further elaborated with pendant glucosyl moieties for improved blood–brain barrier targeting (see structure; R=phenyl, 4-hydroxyphenyl). Glycosidase removal of the carbohydrate substituents gives ligands that are ready to passivate excess metal ions, especially copper and zinc, in the brain. These molecules are potential prodrugs for treatment of neurodegenerative diseases, including Alzheimer's disease.

    26. Chromium–Carbyne Complexes: Intermediates for Organic Synthesis (pages 1719–1722)

      Romain Bejot, Anyu He, John R. Falck and Charles Mioskowski

      Version of Record online: 17 JAN 2007 | DOI: 10.1002/anie.200604015

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      On the same route: Chromium-carbyne complexes are readily prepared by treatment of 1,1,1-trichloromethyl reagents with chromium(II) chloride. They serve as intermediates in the selective formation of a wide variety of products, such as alkynes, alkenes, β-hydroxy ketones, aldehydes, allylic alcohols, and allenes (see scheme, E=electrophile).

    27. A 9-Borylated Acridinyl Radical (pages 1723–1725)

      Ching-Wen Chiu and François P. Gabbaï

      Version of Record online: 19 JAN 2007 | DOI: 10.1002/anie.200604119

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      An odd molecule with an unpaired electron: Reduction of a cationic borane bearing an α-methylium center leads to the formation of a neutral radical, which has been studied by X-ray analysis and EPR spectroscopy. The computed spin density (see picture, right) of this radical shows substantial localization of the unpaired electron in a polarized B[BOND]C π-bonding orbital, a conclusion corroborated by an unusually short B[BOND]C bond.

    28. Domino Ring-Opening/Recyclization Reactions of Doubly Activated Cyclopropanes as a Strategy for the Synthesis of Furoquinoline Derivatives (pages 1726–1729)

      Zhiguo Zhang, Qian Zhang, Shaoguang Sun, Tao Xiong and Qun Liu

      Version of Record online: 19 JAN 2007 | DOI: 10.1002/anie.200604276

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      In one easy step, doubly activated cyclopropanes 1 can be transformed into furoquinoline derivatives 2 through a tandem ring-opening/recyclization reaction mediated by SnCl4⋅5 H2O. A variety of substrates 1 derived from cheap starting materials were converted into the corresponding furoquinolines in good to excellent yields with high chemo- and regioselectivity. R=H, Me, OMe, Cl, or aromatic group is naphthyl.

    29. Copper-Catalyzed Synthesis of N-Sulfonyl-1,2,3-triazoles: Controlling Selectivity (pages 1730–1733)

      Eun Jeong Yoo, Mårten Ahlquist, Seok Hwan Kim, Imhyuck Bae, Valery V. Fokin, K. Barry Sharpless and Sukbok Chang

      Version of Record online: 19 JAN 2007 | DOI: 10.1002/anie.200604241

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      4-Substituted 1-(N-sulfonyl)-1,2,3-triazoles are selectively obtained by using the Cu-catalyzed azide–alkyne cycloaddition reaction with sulfonyl azides. Performing the reaction at 0 °C in chloroform in the presence of 2,6-lutidine and CuI as the catalyst effectively prevents the ketenimine pathway and provides convenient access to N-sulfonyltriazoles in good to excellent yields.

    30. Accelerating Reactions with Microreactors at Elevated Temperatures and Pressures: Profiling Aminocarbonylation Reactions (pages 1734–1737)

      Edward R. Murphy, Joseph R. Martinelli, Nikolay Zaborenko, Stephen L. Buchwald and Klavs F. Jensen

      Version of Record online: 19 JAN 2007 | DOI: 10.1002/anie.200604175

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      Squeeze play: Pressurized microreactor systems greatly expand the range of reaction conditions and accelerate gas–liquid mass transfer. Heck aminocarbonylation reactions (see scheme) exemplify the potential for the quick and safe scanning of reagents and reaction conditions. The yield of amide increases with an increase in temperature and the selectivity for α-ketoamide production (n=2) increases at lower temperature and higher pressure.

    31. syn-Selective and Enantioselective Direct Cross-Aldol Reactions between Aldehydes Catalyzed by an Axially Chiral Amino Sulfonamide (pages 1738–1740)

      Taichi Kano, Yukako Yamaguchi, Youhei Tanaka and Keiji Maruoka

      Version of Record online: 23 JAN 2007 | DOI: 10.1002/anie.200604640

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      Complementary to proline: An axially chiral amino sulfonamide (S)-1 was successfully applied as the catalyst to the direct cross-aldol reaction between two different aldehydes (see scheme; NMP=N-methylpyrrolidone). This catalyst has the advantage of giving mainly syn products, while proline shows the opposite anti selectivity.

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