Chemistry - A European Journal

Cover image for Chemistry - A European Journal

July 20, 2009

Volume 15, Issue 29

Pages 6991–7251

  1. Cover Picture

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    3. Graphical Abstract
    4. News
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    1. Cover Picture: Mechanisms in the Reaction of Palladium(II)–π-Allyl Complexes with Aryl Halides: Evidence for NHC Exchange Between Two Palladium Complexes (Chem. Eur. J. 29/2009) (page 6991)

      Adrien T. Normand, Mikhail S. Nechaev and Kingsley J. Cavell

      Version of Record online: 13 JUL 2009 | DOI: 10.1002/chem.200990107

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      Migrating birds N-heterocyclic carbenes (NHCs) are known to form strong bonds with transition-metal complexes. In their Full paper on page 7063 ff., A. T. Normand, M. S. Nechaev, and K. J. Cavell describe a family of palladium(II) NHC complexes that undergo an autocatalytic reaction with aryl electrophiles in which no less than three Pd[BOND]NHC bonds are sequentially broken. The key step of this process is the concerted transfer of NHC and iodide ligands between two palladium complexes (see cover). This behavior is reminiscent of that of migrating birds, which have strong ties with their breeding grounds, but can travel away from them. In the case of NHCs, traveling too far can lead to a fatal issue if they “land” on a palladium complex from which reductive elimination can occur. Photography by Tim Holte, design by Joëlle Charpy.

  2. Graphical Abstract

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    3. Graphical Abstract
    4. News
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  3. News

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  4. Review

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    1. Supramolecular Chemistry

      Supramolecular Chemistry at Interfaces: Molecular Recognition on Nanopatterned Porous Surfaces (pages 7004–7025)

      Davide Bonifazi, Stefan Mohnani and Anna Llanes-Pallas

      Version of Record online: 30 JUN 2009 | DOI: 10.1002/chem.200900900

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      Programming porosity: This review highlights recent strategies to prepare nanopatterned functional surfaces through self-assembly of organic molecular modules. Use of this method allows easy design and programming at the molecular level of 2D architectures onto surfaces (see scheme) to give periodic cavities capable of hosting functional molecules with potential applications, such as nanomedicine, molecular-based memory storage and sensors.

  5. Communications

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    1. Atropisomerism

      Atropisomerism of α,β-Unsaturated Amidines: Stereoselective Synthesis by Catalytic Cascade Reaction and Optical Resolution (pages 7026–7030)

      Naoya Shindoh, Yoshiji Takemoto and Kiyosei Takasu

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200901103

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      Torquoselective: Enantiomers of axially chiral α,β-unsaturated amidines were prepared by catalytic cascade reactions consisting of [2+2] cycloaddition and thermal cycloreversion. The cascade reaction proceeds in a stereoselective (torquoselective) manner, confirmed by the intermediate depicted.

    2. Organocatalysis

      Asymmetric Synthesis of 3-Amino-δ-lactams and Benzo[a]quinolizidines by Catalytic Cyclization Reactions Involving Azlactones (pages 7031–7034)

      Jun Jiang, Jian Qing and Liu-Zhu Gong

      Version of Record online: 16 JUN 2009 | DOI: 10.1002/chem.200900814

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      The three-component formal [4+2] cycloaddition reaction of azlactones, cinnamaldehydes, and primary amines using phosphoric acid as the catalyst provides access to nitrogenous structural motifs (see scheme), which are found in numerous natural and unnatural products that exhibit important biological activities, such as 3-amino-3,4-dihydropyridinones, benzo[a]quinolizidines, 3-amino-δ-lactams, and 3-aminopiperidinones.

    3. Formal Highly Enantioselective Organocatalytic Addition of Fluoromethyl Anion to α,β-Unsaturated Aldehydes (pages 7035–7038)

      Andrea-Nekane Alba, Xavier Companyó, Albert Moyano and Ramon Rios

      Version of Record online: 23 JUN 2009 | DOI: 10.1002/chem.200900991

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      Symmetric fluoromethylation made easy: A highly enantioselective fluoromethyl addition to α,β-unsaturated aldehydes is described (see scheme). The synthesis of chiral fluorinated blocks, including δ-fluoro-β-aminoalcohol derivatives is disclosed.

    4. Asymmetric Organcatalysis

      Highly Enantioselective Sulfenylation of β-Ketoesters: H-Bond Acceptor Catalysis (pages 7039–7043)

      Ling Fang, Aijun Lin, Hongwen Hu and Chengjian Zhu

      Version of Record online: 16 JUN 2009 | DOI: 10.1002/chem.200901099

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      A new mode of activation: The asymmetric diarylprolinol-catalyzed α-sulfenylation of β-ketoesters provides the products in good-to-excellent enantioselectivities and yields. Studies suggest that the sterically bulky secondary amines activate β-ketoesters through hydrogen bonding. Lg=leaving group.

    5. Cross-Coupling

      Imidazolones in Diastereoselective Cyclization Reactions and CuII-Catalysed Cross-Coupling Reactions (pages 7044–7047)

      Frederik Diness and Morten Meldal

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200900633

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      EASCy: Imidazolones have been synthesized from small peptides and an amino aldehyde building block. Under strongly acidic conditions the imidazolones acted as electrophiles or as nucleophiles in diastereoselective electrophilic aromatic substitution cyclization (EASCy) reactions yielding crude products with purities of 76–99 %. The imidazolones also underwent CuII-catalysed N2/5-arylation generating highly pure amino acid derived heterocyclic scaffolds.

    6. Polymorphism

      Electrochemical Genotyping by Using Two Ferrocene/Isoquinoline-Connected DNA Probes with Different Redox Potentials on a Single Electrode (pages 7048–7051)

      Reona Ikeda, Satoshi Kitagawa, Junya Chiba and Masahiko Inouye

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200900368

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      A single electrode: We describe an electrochemical single-nucleotide polymorphism genotyping protocol using a single electrode that is modified with a ferrocene/isoquinoline conjugate connected to DNA probes, which possess different redox potentials. Three types of zygotes (a wild-type homozygote, a mutant homozygote, and a heterozygote) were identified by a single square wave voltammetric measurement.

  6. Full Papers

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    1. Nanocatalysis

      Cooperative Acid–Base Effects with Functionalized Mesoporous Silica Nanoparticles: Applications in Carbon–Carbon Bond-Formation Reactions (pages 7052–7062)

      Sankaranarayanapillai Shylesh, Alex Wagner, Andreas Seifert, Stefan Ernst and Werner R. Thiel

      Version of Record online: 30 JUN 2009 | DOI: 10.1002/chem.200900851

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      Work together: Acid–base bifunctional mesoporous silica materials were prepared by co-condensation of tetraethoxysilane and silanes possessing amino and sulfonic acid groups. The samples showed increased catalytic activity for various one-step reaction cascades compared with the homogeneous catalysts. An acid–base cooperative activation mechanism is proposed (see scheme).

    2. Palladium Complexes

      Mechanisms in the Reaction of Palladium(II)–π-Allyl Complexes with Aryl Halides: Evidence for NHC Exchange Between Two Palladium Complexes (pages 7063–7073)

      Adrien T. Normand, Mikhail S. Nechaev and Kingsley J. Cavell

      Version of Record online: 2 JUL 2009 | DOI: 10.1002/chem.200900373

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      Strong bonds easily broken: The reaction between a family of PdII–NHC complexes and aryl halides yields 2-arylimidazolium salts with complete selectivity. The mechanism of this intriguing reaction was investigated by kinetic experiments and DFT calculations. An autocatalytic ligand transfer mechanism is shown to operate and strong evidence was found for an unusual NHC exchange between two palladium complexes.

    3. Zincation

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      Structurally Defined Potassium-Mediated Zincation of Pyridine and 4-R-Substituted Pyridines (R=Et, iPr, tBu, Ph, and Me2N) by Using Dialkyl–TMP–Zincate Bases (pages 7074–7082)

      William Clegg, Ben Conway, David V. Graham, Eva Hevia, Alan R. Kennedy, Robert E. Mulvey, Luca Russo and Dominic S. Wright

      Version of Record online: 16 JUN 2009 | DOI: 10.1002/chem.200900549

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      Metal cooperation: The direct zincation of various 4-substituted pyridines at the 2-position by potassium–dialkyl–TMP–zincate bases is manifested in novel dimeric dipotassium-capped anthracene-like structures with coordinatively saturated zinc centers (see figure).

    4. High-Field Relaxivities

      A Gadolinium-Binding Cyclodecapeptide with a Large High-Field Relaxivity Involving Second-Sphere Water (pages 7083–7093)

      Célia S. Bonnet, Pascal H. Fries, Serge Crouzy, Olivier Sénèque, Federico Cisnetti, Didier Boturyn, Pascal Dumy and Pascale Delangle

      Version of Record online: 16 JUN 2009 | DOI: 10.1002/chem.200900636

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      Second-sphere relaxation! Owing to its two inner-sphere water molecules, the Gd3+ complex of the cyclodecapeptide c(DREPGEWDPG) induces particularly large high-field relaxivities of the water protons. Interpretation of the high-field contributions to relaxivity with independently determined molecular parameters evidences a strong second-sphere mechanism caused by interactions of water molecules with the hydrophilic peptide scaffold (see figure).

    5. Ionogel Catalysts

      The Co-Entrapment of a Homogeneous Catalyst and an Ionic Liquid by a Sol–gel Method: Recyclable Ionogel Hydrogenation Catalysts (pages 7094–7100)

      Steven J. Craythorne, Kris Anderson, Fabio Lorenzini, Christina McCausland, Emily F. Smith, Peter Licence, Andrew C. Marr and Patricia C. Marr

      Version of Record online: 16 JUN 2009 | DOI: 10.1002/chem.200801809

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      An ionogel protected catalyst: An ionic-liquid-modified sol–gel method for the synthesis of catalytic materials from homogeneous catalysts is described. The resultant materials (pictured here) are highly active, selective and leach resistant and exhibit excellent recycling. The catalyst is protected within the nano-sized pores of the ionogel matrix.

    6. Ionic Radii

      On the Size of Ions Solvated in Helium Clusters (pages 7101–7108)

      Filipe Ferreira da Silva, Philipp Waldburger, Stefan Jaksch, Andreas Mauracher, Stephan Denifl, Olof Echt, Tilmann D. Märk and Paul Scheier

      Version of Record online: 16 JUN 2009 | DOI: 10.1002/chem.200802554

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      How large are they? The size of ions depends on the solvent. What's their size when solvated in liquid helium (see picture)? Mass spectra of halogen anions, cations, and molecular cations complexed with helium atoms exhibit conspicuous abundance drops when the number of helium atoms reaches a value characteristic for each ion, indicating closure of a solvation shell. Ionic radii are deduced from these values.

    7. Aminoglycoside Mimics

      Design of tRNALys3 Ligands: Fragment Evolution and Linker Selection Guided by NMR Spectroscopy (pages 7109–7116)

      Florence Chung, Carine Tisné, Thomas Lecourt, Bili Seijo, Frédéric Dardel and Laurent Micouin

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200802451

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      Off the beaten tracks: A modular approach for the design of micromolar tRNALys3 ligands from millimolar fragments has been established (see graphic). The use of NMR spectroscopy has proved to be very useful in this approach, not only to detect low-affinity complexes between small compounds and RNA, but also to provide information for linker-length estimation and binding-site localisation.

    8. Natural Products

      Synthesis and Biophysical Studies on 35-Deoxy Amphotericin B Methyl Ester (pages 7117–7128)

      Alex M. Szpilman, Damiano M. Cereghetti, Jeffrey M. Manthorpe, Nicholas R. Wurtz and Erick M. Carreira

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200900231

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      A modular strategy for the efficient assembly of amphotericin B analogues bearing modifications in the macrolactone ring is presented. The strategy relies on the efficient gram-scale preparation of all the subunits of amphotericin B. Synthesis and biophysical studies on 35-deoxy ampphotericin B provide new clues to the mode of action of amphotericin B.

    9. Coordination Compounds

      Nb and Ta Adducts: Connecting d0 Metal Chlorides and Phosphorus Sulfide Cages (pages 7129–7138)

      Diana Hoppe, Dominik Schemmel, Martin Schütz and Arno Pfitzner

      Version of Record online: 16 JUN 2009 | DOI: 10.1002/chem.200900370

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      Weak-bonding coordination compounds: Adducts of TaCl5 and NbCl5 with various P4Sn cage molecules were prepared and characterized. Ab initio calculations reveal that the coordinative bond is very weak and the binding energy is governed mainly by long-range van der Waals dispersion.

    10. Dendrimers

      Dendrimer Disassembly in the Gas Phase: A Cascade Fragmentation Reaction of Fréchet Dendrons (pages 7139–7149)

      Bilge Baytekin, H. Tarik Baytekin, Uwe Hahn, Werner Reckien, Barbara Kirchner and Christoph A. Schalley

      Version of Record online: 16 JUN 2009 | DOI: 10.1002/chem.200900403

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      Self-immolation! Fréchet dendrons disassemble in the gas-phase. The process is triggered by detachment of the focal amine. Tandem MS experiments reveal an intriguing cascade fragmentation mechanism.

    11. Borylene Complexes

      Synthesis, Structure, and Bonding of Novel Homodinuclear Cobalt and Nickel Borylene Complexes (pages 7150–7155)

      Holger Braunschweig, Bastian Christ, Miriam Colling-Hendelkens, Melanie Forster, Kathrin Götz, Martin Kaupp, Krzysztof Radacki and Fabian Seeler

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200900679

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      Building bridges: Photochemically induced borylene transfer to cobalt and nickel carbonyl complexes, [CpCo(CO)2] and [Cp2Ni2(CO)2] from [(OC)5M[DOUBLE BOND]BN(SiMe3)2] (M=Cr, W) generates the first instances of homodinuclear bridged cobalt and nickel (see figure) borylene complexes featuring bridging CO ligands.

    12. Lipopolysaccharides

      Structural Study and Conformational Behavior of the Two Different Lipopolysaccharide O-Antigens Produced by the Cystic Fibrosis Pathogen Burkholderia multivorans (pages 7156–7166)

      Teresa Ieranò, Alba Silipo, Paola Cescutti, Maria Rosaria Leone, Roberto Rizzo, Rosa Lanzetta, Michelangelo Parrilli and Antonio Molinaro

      Version of Record online: 16 JUN 2009 | DOI: 10.1002/chem.200900647

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      Two different endotoxins: Burkholderia multivorans is an opportunistic human pathogen isolated in a cystic fibrosis center and causative of an outbreak with lethal outcome. The three-dimensional structures of the two O-antigens (one of which is shown in the figure) produced by a highly virulent clinical isolate have been determined.

    13. Ambifunctional Catalysis

      The AZARYPHOS Family of Ligands for Ambifunctional Catalysis: Syntheses and Use in Ruthenium-Catalyzed anti-Markovnikov Hydration of Terminal Alkynes (pages 7167–7179)

      Lukas Hintermann, Tuan Thanh Dang, Aurélie Labonne, Thomas Kribber, Li Xiao and Pance Naumov

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200900563

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      A combined effort: More than 25 AZARYPHOS (aza–aryl–phosphane) ligands for ambifunctional catalysis by a metal and a nitrogen lone pair have been obtained by general and scalable syntheses (see graphic). The simple access to a family of bifunctional ligands opens a door to ligand screening approaches.

    14. Cage Compounds

      Molecular Nitrides with Titanium and Group 13–15 Elements (pages 7180–7191)

      María García-Castro, Avelino Martín, Miguel Mena and Carlos Yélamos

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200900660

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      Heterometallic nitrido complexes containing single-cube [MTi3N4], corner-shared double-cube [MTi6N8], or the unprecedented (see picture) corner-linked double-cube [Ga2Ti6N8] cores were obtained by reaction of [{Ti(η5-C5Me5)(μ-NH)}33-N)] with amido [M(NR2)x] Group 13–15 derivatives.

    15. Grignard Reaction

      Preparation of Polyfunctional Arylmagnesium, Arylzinc, and Benzylic Zinc Reagents by Using Magnesium in the Presence of LiCl (pages 7192–7202)

      Fabian M. Piller, Albrecht Metzger, Matthias A. Schade, Benjamin A. Haag, Andrei Gavryushin and Paul Knochel

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200900575

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      Metal-driven: The preparation of functionalized zinc and magnesium reagents is reported. LiCl catalyzes the insertion of Mg and Zn into various aromatic and heterocyclic bromides (see scheme). Several functional groups, such as -OBoc, -OTs, -Cl, -F, -CF3, -OMe, -OPiv, -OAc, -NMe2, and -N2NR2, are well tolerated under these new mild conditions. Zn/LiCl and Mg/LiCl lead to orthogonal regioselectivities for insertions into polybrominated arenes. Large-scale reactions have been performed.

    16. Multicomponent Systems

      Multicomponent Supramolecular Systems: Self-Organization in Coordination-Driven Self-Assembly (pages 7203–7214)

      Yao-Rong Zheng, Hai-Bo Yang, Koushik Ghosh, Liang Zhao and Peter J. Stang

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200900230

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      Organize yourself! A variety of 2 D polygons (rectangles, triangles, and rhomboids) and 3 D cages (triangular prisms and distorted and nondistorted trigonal bipyramids) can be simultaneously and selectively formed in one pot via self-organization upon mixing various organoplatinum acceptors and pyridyl donors of differing geometry (see figure).

    17. Aromatic Azido Reduction

      Chemoselective Aromatic Azido Reduction with Concomitant Aliphatic Azide Employing Al/Gd Triflates/NaI and ESI-MS Mechanistic Studies (pages 7215–7224)

      Ahmed Kamal, Nagula Markandeya, Nagula Shankaraiah, C. Ratna Reddy, S. Prabhakar, C. Sanjeeva Reddy, Marcos N. Eberlin and Leonardo Silva Santos

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200900853

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      Aromatic azido reduction! Aluminium and gadolinium triflates catalyze the chemoselective reduction of aromatic azides to the corresponding amines in combination with sodium iodide by an intramolecular azido reductive tandem cyclization reaction (see scheme). This methodology selectively reduces aryl azides with enhanced yields and proceeds in a shorter reaction time. The mechanistic aspects have been investigated by online monitoring of the reaction employing ESI-MS.

    18. Phosphorescence

      Emissive or Nonemissive? A Theoretical Analysis of the Phosphorescence Efficiencies of Cyclometalated Platinum(II) Complexes (pages 7225–7237)

      Glenna So-Ming Tong and Chi-Ming Che

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200802485

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      Don't flip out, emit! DFT calculations can explain the different phosphorescence efficiencies of a family of five structurally similar cyclometalated PtII complexes by considering spin–orbit coupling and electronic structures in the S0 ground and T1 excited states. For example, on going from the S0 to the T1 state, the lateral aryl rings of strongly emitting [Pt(NCN)Cl] (NCN=1,3-bis(2-pyridyl)phenyl) remain coplanar, whereas those of its weakly emissive isomer [Pt(CNN)Cl] (CNN=6-phenyl-2,2′-bipyridyl) flip up due to Jahn–Teller distortion (see picture), which results in a large nonradiative decay rate

    19. One-Pot Reactions

      Preparation of 2-Quinolones by Sequential Heck Reduction–Cyclization (HRC) Reactions by Using a Multitask Palladium Catalyst (pages 7238–7245)

      François-Xavier Felpin, Jérôme Coste, Cécile Zakri and Eric Fouquet

      Version of Record online: 19 JUN 2009 | DOI: 10.1002/chem.200900583

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      Enjoy the simplicity! One-pot sequential Heck reduction–cyclization (HRC) reactions leading to variously substituted 2-quinolones have been developed that use a multitask palladium catalyst under ligand- and base-free conditions at moderate temperature (see scheme).

  7. Preview

    1. Top of page
    2. Cover Picture
    3. Graphical Abstract
    4. News
    5. Review
    6. Communications
    7. Full Papers
    8. Preview
    1. You have free access to this content
      Preview: Chem. Eur. J. 30/2009 (page 7251)

      Version of Record online: 13 JUL 2009 | DOI: 10.1002/chem.200990110

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