Chemistry - A European Journal

Cover image for Vol. 17 Issue 25

June 14, 2011

Volume 17, Issue 25

Pages 6873–7119

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Back Cover
    4. Graphical Abstract
    5. News
    6. Minireview
    7. Communications
    8. Full Papers
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    1. Cover Picture: Cycloaddition Reactions of a Chromium–Chromium Quintuple Bond (Chem. Eur. J. 25/2011) (page 6873)

      Dr. Awal Noor, Emmanuel Sobgwi Tamne, Dr. Sadaf Qayyum, Tobias Bauer and Prof. Dr. Rhett Kempe

      Version of Record online: 3 JUN 2011 | DOI: 10.1002/chem.201190125

      Thumbnail image of graphical abstract

      Addition reactions of alkynes and dienes to a quintuply bonded dichromium complex are reported by R. Kempe et al. in their Communication on page 6900 ff. Both alkynes and dienes undergo cycloaddition reactions in which the formal bond order of the Cr[BOND]Cr bond is reduced. Cr[BOND]Cr quintuple bonds can undergo similar (cycloaddition) reactions as well-understood C[BOND]C double and triple bonds. The picture in the background is the Festspielhaus, Bayreuth (photo by Jana Kempe).

  2. Back Cover

    1. Top of page
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    3. Back Cover
    4. Graphical Abstract
    5. News
    6. Minireview
    7. Communications
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    1. Back Cover: Proton-Induced Tuning of Metal–Metal Communication in Rack-Type Dinuclear Ru Complexes Containing Benzimidazolyl Moieties (Chem. Eur. J. 25/2011) (page 6874)

      Katsuaki Kobayashi, Masamichi Ishikubo, Katsuhiko Kanaizuka, Keiko Kosuge, Shigeyuki Masaoka, Prof. Ken Sakai, Prof. Koichi Nozaki and Prof. Masa-aki Haga

      Version of Record online: 3 JUN 2011 | DOI: 10.1002/chem.201190129

      Thumbnail image of graphical abstract

      Rack-type Ru complexes that act as a bibasic acid and bear a bis-tridentate benzimidazolyl ligand have been synthesized. Spectral and electrochemical properties are discussed in the Full Paper by M. Haga et al. on page 6954 ff., from the viewpoint of the influence of protonation/deprotonation on the benzimidazolyl groups. In particular, the tuning of metal–metal electronic communication by protonation/deprotonation in mixed- valence dinuclear complexes was investigated.

  3. Graphical Abstract

    1. Top of page
    2. Cover Picture
    3. Back Cover
    4. Graphical Abstract
    5. News
    6. Minireview
    7. Communications
    8. Full Papers
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  4. News

    1. Top of page
    2. Cover Picture
    3. Back Cover
    4. Graphical Abstract
    5. News
    6. Minireview
    7. Communications
    8. Full Papers
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  5. Minireview

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    4. Graphical Abstract
    5. News
    6. Minireview
    7. Communications
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    1. Organocatalysis

      Squaramides: Bridging from Molecular Recognition to Bifunctional Organocatalysis (pages 6890–6899)

      Dr. José Alemán, Dr. Alejandro Parra, Hao Jiang and Prof. Dr. Karl Anker Jørgensen

      Version of Record online: 17 MAY 2011 | DOI: 10.1002/chem.201003694

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      New dimensions for squaramides: In this minireview, squaramides are presented from their roots as artificial anion receptors in molecular recognition studies to the new advances in their application in asymmetric organocatalysis as powerful bifunctional hydrogen-bonding catalysts. The main features of the squaramido functionality and direct comparison with analogous ureas and thioureas are also discussed.

  6. Communications

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    1. Multiple Bonds

      Cycloaddition Reactions of a Chromium–Chromium Quintuple Bond (pages 6900–6903)

      Dr. Awal Noor, Emmanuel Sobgwi Tamne, Dr. Sadaf Qayyum, Tobias Bauer and Prof. Dr. Rhett Kempe

      Version of Record online: 13 MAY 2011 | DOI: 10.1002/chem.201100841

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      Give me five! Addition of alkynes as well as dienes to a quintuply bonded dichromium complex was investigated and cycloaddition reactions were observed (see scheme). The structures of the obtained compounds indicate the reduction of the alkyne and diene ligands, an oxidation of the chromium atoms, as well as the decrease of the Cr[BOND]Cr bond order.

    2. C[BOND]H Arylation

      Palladium-Catalyzed Direct Arylations of Azoles with Aryl Silicon and Tin Reagents (pages 6904–6908)

      Wei Han, Dr. Peter Mayer and Dr. Armin R. Ofial

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201100037

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      Regioselective arylations of imidazoles, oxazoles, and thiazoles were achieved by palladium-catalyzed cross-coupling with trialkoxy(aryl)silanes or allyltriphenylstannane (see scheme). Addition of ligands or exclusion of moisture was not necessary to obtain C2-substituted azoles in high yields.

    3. Metal–Metal Bonds

      An Unsupported Uranium–Rhenium Complex Prepared by Alkane Elimination (pages 6909–6912)

      Benedict M. Gardner, Dr. Jonathan McMaster, Fabrizio Moro, Dr. William Lewis, Prof. Alexander J. Blake and Dr. Stephen T. Liddle

      Version of Record online: 6 MAY 2011 | DOI: 10.1002/chem.201100682

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      An unsupported uranium–rhenium bond has been prepared by alkane elimination by treatment of a cyclometallated alkyl uranium triamidoamine complex with rhenocene hydride (see scheme). DFT analysis reveals σ and π combinations in the U[BOND]Re bond, but the rhenium contributions dominate and an atoms-in-molecules analysis reveals a closed-shell, predominantly ionic uranium–rhenium interaction.

    4. Cross-Coupling

      Palladium-Catalyzed Borylation of Aryl Mesylates and Tosylates and Their Applications in One-Pot Sequential Suzuki–Miyaura Biaryl Synthesis (pages 6913–6917)

      Wing Kin Chow, Dr. Chau Ming So, Prof. Dr. Chak Po Lau and Prof. Dr. Fuk Yee Kwong

      Version of Record online: 5 MAY 2011 | DOI: 10.1002/chem.201100361

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      Top of the one-pots! The first palladium-catalyzed borylation of aryl tosylates and mesylates is described. The reaction conditions are mild and provide excellent functional-group compatibility (e.g., R=CN, CHO, COOMe, C(O)R, NH2, or NH-indole; see scheme). Pd/MeO-CM-phos allows one-pot sequential reactions in the preparation of unsymmetrical biaryls.

    5. Pd Catalysis

      Palladium-Catalyzed Coupling of Propargylic Carbonates with N-Tosylhydrazones: Highly Selective Synthesis of Substituted Propargylic N-Sulfonylhydrazones and Vinylallenes (pages 6918–6921)

      Dr. Zi-Sheng Chen, Dr. Xin-Hua Duan, Dr. Lu-Yong Wu, Shaukat Ali, Ke-Gong Ji, Ping-Xin Zhou, Xue-Yuan Liu and Prof. Dr. Yong-Min Liang

      Version of Record online: 12 MAY 2011 | DOI: 10.1002/chem.201100248

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      An efficient palladium-catalyzed coupling of propargylic carbonates (1) with N-tosylhydrazones (2, 2′) has been carried out. A wide range of propargylic N-sulfonylhydrazones (3) and multisubstituted vinylallenes (4) can be obtained selectively by using either [PdCl2(CH3CN)2] or [Pd2(dba)3] as catalysts. (dba=trans,trans-dibenzylideneacetone, dppp=propane-l,3-diylbis(diphenylphosphane), Ts=4-toluenesulfonyl.)

    6. Synthetic Methods

      Catalyst-Free Regio- and Stereospecific Synthesis of β-Sulfonamido Dithiocarbamates: Efficient Ring-Opening Reactions of N-Tosyl Aziridines by Dialkyldithiocarbamates (pages 6922–6925)

      Kaliyamoorthy Alagiri and Dr. Kandikere Ramaiah Prabhu

      Version of Record online: 6 MAY 2011 | DOI: 10.1002/chem.201100817

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      Lord of the ring-opening! A metal-free strategy involving ring-opening of aziridines by the sodium salt of dialkyldithiocarbamate has been employed to give a variety of β-sulfonamido dithiocarbamates. The in situ generation of dialkyldithiocarbamates provided a simple, user-friendly, one-pot reaction that gives aziridine ring-opened products (see scheme; Ts=tosyl; R=alkyl; R1, R2=alkyl, cycloalkyl).

    7. Nanostructures

      Luminescent, Colloidal, F-Substituted, Hydroxyapatite Nanocrystals (pages 6926–6930)

      Dr. Junfeng Hui and Prof. Dr. Xun Wang

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201100680

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      Shiny, HAp(py) crystals: Luminescent, colloidal, F-substituted, hydroxyapatite (FHAp) nanocrystals have been synthesized by rare-earth-ion doping, which showed green emission in solutions and films and red emission in a polymer matrix. Due to the wide availability and excellent mechanical and biologically compatible properties, these luminescent nanocrystals may find applications in biological labeling, luminescent polymers, and so forth.

    8. Sensors

      Chromogenic, Specific Detection of the Nerve-Agent Mimic DCNP (a Tabun Mimic) (pages 6931–6934)

      Santiago Royo, Prof. Ana M. Costero, Prof. Margarita Parra, Dr. Salvador Gil, Prof. Ramón Martínez-Máñez and Dr. Félix Sancenón

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201100602

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      Nerve-gas detection: An azo dye with pyridine and aniline moieties can selectively detect diethylcyanophosphonate (DCNP) from diisopropylfluorophosphate (DFP) and diethylchlorophosphate (DCP) by colour changes. Upon addition of DFP and DCP a phosphorylation in the pyridine occurs with a colour change from orange to magenta, whereas addition of DCNP phosphorylated the aniline ring with a colour change from orange to yellow (see figure).

      Corrected by:

      Corrigendum: Corrigendum: Chromogenic, Specific Detection of the Nerve-Agent Mimic DCNP (a Tabun Mimic)

      Vol. 17, Issue 30, 8242, Version of Record online: 13 JUL 2011

    9. Homogeneous Catalysis

      Activity Enhancement of a Catalyst System for the Selective Trimerization of Ethene to 1-Hexene by Modification of the Chromium to Chloride to Aluminium Ratio (pages 6935–6938)

      Dr. Bernd H. Müller, Dr. Normen Peulecke, Dr. Stephan Peitz, Dr. Bhaskar R. Aluri, Prof. Dr. Uwe Rosenthal, Dr. Mohammed H. Al-Hazmi, Fuad M. Mosa, Dr. Anina Wöhl and Dr. Wolfgang Müller

      Version of Record online: 10 MAY 2011 | DOI: 10.1002/chem.201003463

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      Fighting for chloride: A novel catalyst system for ethene trimerization consisting of chromium acetylacetonate, the ligand Ph2PN(iPr)P(Ph)N(iPr)H, triethylaluminium, and ionic modifiers has been investigated. Chloride has been identified as an important component of this catalytic system: An optimized [Cr]/[Cl]/[Al] ratio enhances the catalytic activity while the selectivity of the reaction remains unaffected (see scheme; acac=acetylacetonate).

  7. Full Papers

    1. Top of page
    2. Cover Picture
    3. Back Cover
    4. Graphical Abstract
    5. News
    6. Minireview
    7. Communications
    8. Full Papers
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    1. Bioorganic Chemistry

      Furan-Oxidation-Triggered Inducible DNA Cross-Linking: Acyclic Versus Cyclic Furan-Containing Building Blocks—On the Benefit of Restoring the Cyclic Sugar Backbone (pages 6940–6953)

      Dr. Kristof Stevens, Dr. Diederica D. Claeys, Dr. Saron Catak, Sara Figaroli, Prof. Dr. Michal Hocek, Dr. Jan M. Tromp, Prof. Dr. Stefan Schürch, Prof. Dr. Veronique Van Speybroeck and Prof. Dr. Annemieke Madder

      Version of Record online: 20 MAY 2011 | DOI: 10.1002/chem.201100067

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      Furan—a caged reactive moiety for DNA cross-linking: New phenyl–furan-modified nucleoside building blocks have been employed in inducible DNA interstrand cross-linking. Given the modular nature of the building-block synthesis and the commercial availability of various furan derivatives, the current study demonstrates that the furan-oxidation cross-link strategy allows fine-tuning of selectivity by the precise choice and conformational behavior of the modified furan-containing moiety (see graphic).

    2. Proton-Induced Switching

      Proton-Induced Tuning of Metal–Metal Communication in Rack-Type Dinuclear Ru Complexes Containing Benzimidazolyl Moieties (pages 6954–6963)

      Katsuaki Kobayashi, Masamichi Ishikubo, Katsuhiko Kanaizuka, Keiko Kosuge, Shigeyuki Masaoka, Prof. Ken Sakai, Prof. Koichi Nozaki and Prof. Masa-aki Haga

      Version of Record online: 17 MAY 2011 | DOI: 10.1002/chem.201100074

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      Rack-eteering: Rack-type Ru complexes bearing a bis-tridentate benzimidazolyl ligand have been synthesized. Proton-induced tuning of the metal–metal interaction in the mixed-valence state (see scheme) has been shown experimentally and by theoretical calculations.

    3. Total Synthesis

      Gram-Scale Synthesis of Iejimalide B (pages 6964–6972)

      Dr. Julien Gagnepain, Dr. Emilie Moulin and Prof. Alois Fürstner

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201100178

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      A long way to a short route: The delicacy of the polyunsaturated framework of iejimalide B (see figure), a powerful cytotoxic agent of marine origin, made several rounds of careful optimization necessary before the original laboratory synthesis could be scaled up to provide gram amounts of this valuable material. A panopticum of transition-metal-catalyzed transformations made this success possible, amongst which the selective activation of two out of ten different alkenes of the cyclization precursor with the aid of a Grubbs catalyst is most noteworthy.

    4. Natural Products

      Molecular Editing and Assessment of the Cytotoxic Properties of Iejimalide and Progeny (pages 6973–6984)

      Dr. Julien Gagnepain, Dr. Emilie Moulin, Dr. Cristina Nevado, Dr. Mario Waser, Dr. Armin Maier, Dr. Gerhard Kelter, Prof. Heinz-Herbert Fiebig and Prof. Alois Fürstner

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201100180

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      Editing and reading out: An interplay between systematic molecular editing and biological screening led to a series of fully synthetic iejimalide analogues, which show impressive tumor selectivity and a remarkable potency in a tumor-colony assay. Although IC50 values as low as ≤1 nM could be reached, preliminary in vivo studies indicate a possible metabolic instability and hence the need for further structural modification.

    5. Main Group Metal Oxides

      Hydrolysis of a Basic Bismuth Nitrate—Formation and Stability of Novel Bismuth Oxido Clusters (pages 6985–6990)

      Linda Miersch, Maik Schlesinger, Ralf W. Troff, Prof. Dr. Christoph A. Schalley, Tobias Rüffer, Prof. Dr. Heinrich Lang, Prof. Dr. Dirk Zahn and Prof. Dr. Michael Mehring

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201100673

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      BiO-graphical route: Hydrolysis of bismuth nitrate provides bismuth oxido clusters with a {Bi38O45}-core structure that presents a cutout of bulk δ-Bi2O3. Exchange of nitrate anions for tosylate ligands does not alter the core structure but enhances the solubility. The bismuth oxido clusters are stable after dissolution as shown by ESI-MS studies, but fragment after laser irradiation in the gas phase. Infrared multi-photon dissociation (IRMPD) mass spectrometry reveals loss of N2O5 in accordance to thermal analysis.

    6. [2.2]Cyclophanedienes

      Synthesis and Ring-Opening Metathesis of Tetraalkoxy-Substituted [2.2]Paracyclophane-1,9-dienes (pages 6991–6997)

      Dr. Chin-Yang Yu, Dr. Madeleine Helliwell, Dr. James Raftery and Prof. Michael L. Turner

      Version of Record online: 5 MAY 2011 | DOI: 10.1002/chem.201003147

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      Playing twister: Tetraalkoxy-substituted [2.2]paracyclophanedienes can be prepared in three steps from dithia[3.3]cyclophanes as a mixture of pseudo-geminal and pseudo-ortho diastereomers. X-ray crystallography shows that these compounds are highly strained with heavily distorted aromatic rings. Ring-opening metathesis using the Grubbs' second-generation catalyst is selective for only the pseudo-geminal isomer (see scheme; R=octyl).

    7. Photochemistry

      Synthesis, Characterisation and Application of Iridium(III) Photosensitisers for Catalytic Water Reduction (pages 6998–7006)

      Felix Gärtner, Dr. Daniela Cozzula, Dr. Sebastian Losse, Albert Boddien, Dr. Gopinatan Anilkumar, Dr. Henrik Junge, Dr. Thomas Schulz, Dr. Nicolas Marquet, Dr. Anke Spannenberg, Prof. Dr. Serafino Gladiali and Prof. Dr. Matthias Beller

      Version of Record online: 6 MAY 2011 | DOI: 10.1002/chem.201100235

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      Light-driven water reduction: The synthesis and characterisation of new iridium(III) photosensitisers is described. Active water-reduction systems were established with various water-reduction catalysts (WRCs). The best system contained [Ir(6-iPr-bpy)(ppy)2]PF6 (bpy: 2,2′-bipyridine, ppy: 2-phenylpyridine) and [HNEt3][HFe3(CO)11] together with a P ligand (see figure).

    8. Functionalized Graphene

      Synthesis and Characterization of Red-Luminescent Graphene Oxide Functionalized with Silica-Coated Eu3+ Complex Nanoparticles (pages 7007–7012)

      Chao Zhao, Lingyan Feng, Bailu Xu, Prof. Dr. Jinsong Ren and Prof. Dr. Xiaogang Qu

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201003712

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      Seeing red: Red-luminescent silica-coated Eu3+ complex nanoparticles were synthesized and covalently coupled to graphene oxide (GO) nanosheets (see scheme). They showed strong luminescence, a long lifetime, and potential for highly sensitive time-resolved fluorescence cyto- and histochemistry imaging.

    9. DNA

      Proton-Fueled DNA-Duplex-Based Stimuli-Responsive Reversible Assembly of Single-Walled Carbon Nanotubes (pages 7013–7019)

      Chao Zhao, Konggang Qu, Prof. Jinsong Ren and Prof. Xiaogang Qu

      Version of Record online: 3 MAY 2011 | DOI: 10.1002/chem.201100202

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      Self-assembly of carbon nanotubes: An example of the use of DNA-duplex-based protons (H+) as a fuel to control reversible single-walled carbon nanotube (SWNT) self-assembly has been presented (see scheme; EDC=1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide hydrochloride; sulfo-NHS=sulfo-N-hydroxy succinimide).

    10. Cage Compounds

      Recognition of Oxalate by a Copper(II) Polyaza Macrobicyclic Complex (pages 7020–7031)

      Pedro Mateus, Prof. Rita Delgado, Dr. Paula Brandão and Prof. Vítor Félix

      Version of Record online: 6 MAY 2011 | DOI: 10.1002/chem.201100428

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      Double header: A new heteroditopic macrobicyclic heptaamine was prepared in which one of the head units is appropriate for the coordination of Cu2+, whereas the other is available for additional hydrogen-bonding and electrostatic interactions (see figure). The studies revealed a clear preference for oxalate over the other studied dicarboxylates.

    11. Palladium

      Pd-Catalyzed [2+2+1] Coupling of Alkynes and Arenes: Phenol Diazonium Salts as Mechanistic Trapdoors (pages 7032–7040)

      Prof. Dr. Bernd Schmidt, Dipl.-Chem. René Berger, Alexandra Kelling and Prof. Dr. Uwe Schilde

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201100609

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      A mechanistic trapdoor: The Pd-catalyzed coupling reaction of internal alkynes and an aryl electrophile (see scheme) is trapped on the stage of the spirocycle if phenol diazonium ions are used as coupling reagents. Reconstitution of aromaticity by rearrangement to polysubstituted naphthalenes is not observed under these conditions.

    12. Lanthanides

      Synthesis, Characterization, and DNA-Binding and -Photocleavage Properties of Water-Soluble Lanthanide Porphyrinate Complexes (pages 7041–7052)

      Dr. Xun-Jin Zhu, Dr. Ping Wang, Heidi Wing Chi Leung, Prof. Wai-Kwok Wong, Prof. Wai-Yeung Wong and Prof. Daniel W. J. Kwong

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201003342

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      Wet, wet, wet: Lanthanide complexes with meso-pyridyl-substituted porphyrin and their corresponding water-soluble lanthanide porphyrinate complexes were prepared and fully characterized (see scheme). The photophysical properties of the complexes were investigated in detail, as well as the interaction of water-soluble lanthanide(III) porphyrinate complexes with DNA.

    13. Structure Elucidation

      Structural Investigation and Biological Activity of the Lipooligosaccharide from the Psychrophilic Bacterium Pseudoalteromonas haloplanktis TAB 23 (pages 7053–7060)

      Sara Carillo, Dr. Giuseppina Pieretti, Dr. Ermenegilda Parrilli, Prof. Dr. Maria L. Tutino, Dr. Sabrina Gemma, Dr. Monica Molteni, Prof. Dr. Rosa Lanzetta, Prof. Dr. Michelangelo Parrilli and Prof. Dr. Maria M. Corsaro

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201100579

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      Biological activity: We report the complete structure of the lipooligosaccharide from Pseudoalteromonas haloplanktis TAB 23 (see scheme), a Gram-negative psychrophilic bacterium isolated from the Antarctic coastal sea. The lipid A showed an antagonistic effect on cytokine up-regulation induced by E. coli lipopolysaccharide. The oligosaccharide portion was characterized by 2D NMR spectroscopy.

    14. Foldamers

      A Foldamer at the Liquid/Graphite Interface: The Effect of Interfacial Interactions, Solvent, Concentration, and Temperature (pages 7061–7068)

      Dr. Yong-Tao Shen , Ningbo Zhu, Xue-Mei Zhang, Dr. Ke Deng, Prof. Wei Feng, Qifan Yan, Prof. Shengbin Lei, Prof. Dahui Zhao, Prof. Qing-Dao Zeng and Prof. Chen Wang

      Version of Record online: 6 MAY 2011 | DOI: 10.1002/chem.201003589

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      Folding at an interface: The unfolding process and self-assembly of foldable oligomer 1 at a liquid/solid interface was investigated by STM. At the molecular-conformation level, five molecular conformations were identified (see picture for STM images and structural models). Varying the solvent temperature and/or concentration of foldamer 1 results in different self-assemblies of foldamer 1 as a result of variations in molecular conformation.

    15. Metal–Organic Frameworks

      Uptake of Liquid Alcohols by the Flexible FeIII Metal–Organic Framework MIL-53 Observed by Time-Resolved In Situ X-ray Diffraction (pages 7069–7079)

      Dr. Richard I. Walton, Alexis S. Munn, Dr. Nathalie Guillou and Dr. Franck Millange

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201003634

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      Breathing under control: The expansion of flexible metal–organic frameworks in the presence of simple aliphatic alcohols is observed in real time by in situ powder X-ray diffraction (see figure); this shows how metastable partially expanded phases may be isolated by fluorination of the metal–organic framework.

    16. pKas of Aminosugars

      Quantifying the Electronic Effects of Carbohydrate Hydroxy Groups by Using Aminosugar Models (pages 7080–7086)

      Dr. Christian M. Pedersen, Jacob Olsen, Azra B. Brka and Prof. Dr. Mikael Bols

      Version of Record online: 3 MAY 2011 | DOI: 10.1002/chem.201100020

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      Aminosugar basicity trends: The relative electron densities of aminosugars as model compounds have been determined by pKa measurements and compared with the corresponding sugars. The stereoelectronic effects of the substituents on the sugars as well as the ring oxygen can, to a large extent, explain the differences in the pKa values of the amino groups and hence the differences in the nucleophilicity of the corresponding hydroxy groups (see figure).

    17. Supramolecular Chemistry

      Oligo(p-phenylene-ethynylene)s with Backbone Conformation Controlled by Competitive Intramolecular Hydrogen Bonds (pages 7087–7094)

      Dr. Wei Hu, Qifan Yan and Prof. Dahui Zhao

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201003603

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      Planar or not: By implementing two competitive sets of intramolecular hydrogen bonds, oligo(p-phenylene-ethynylene)s of planar or non-planar backbone conformation were obtained. The strength of related hydrogen bonds in the side chains was modulated by the size of the ring formed by the back-folded oligo(ethylene glycol) unit. Thereby, the competing hydrogen bonds confining the relative orientation of the phenylene units in the backbone were switched on or off, to give planar or non-planar conformations (see scheme for an example).

    18. Supported Catalysts

      Selective Modification of the Acid–Base Properties of Ceria by Supported Au (pages 7095–7104)

      Manuela C. I. Bezen, Dr. Cornelia Breitkopf, Nadia El Kolli, Jean-Marc Krafft, Dr. Catherine Louis and Prof. Dr. Johannes A. Lercher

      Version of Record online: 6 MAY 2011 | DOI: 10.1002/chem.201002011

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      Au supported on CeO2 acts in two ways as a surface modifier. First, it either blocks access to or reduces Ce4+ to Ce3+. Second, the resulting Au species (presumably Au+ ions) act as soft, weak Lewis acid sites stabilizing carbanion intermediates and enhancing hydride abstraction in the dehydrogenation of alcohols. Consequently, the resulting basic catalyst catalyzes dehydrogenation of propan-2-ol to acetone with high efficiency and without notable deactivation (pathway a).

    19. Yttria Microstructures

      Controllable Synthesis of Y2O3 Microstructures for Application in Cataluminescence Gas Sensing (pages 7105–7111)

      Lichun Zhang, Xiaoling Hou, Dr. Ming Liu, Prof. Yi Lv and Prof. Xiandeng Hou 

      Version of Record online: 6 MAY 2011 | DOI: 10.1002/chem.201002626

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      Yttrium oxide dumbbells, nanosheets, and microspheres were controllably synthesized by a facile hydrothermal procedure followed by calcination. Of the three morphologies, the Y2O3 dumbbells (see picture) show the best gas-sensing characteristics for 16 common volatile organic compounds (VOCs) in a cataluminescence sensor.

    20. Catalysis

      Reaction Mechanism of Aerobic Oxidation of Alcohols Conducted on Activated-Carbon-Supported Cobalt Oxide Catalysts (pages 7112–7117)

      Dr. Junjiang Zhu, Prof. Joaquim L. Faria, Prof. José L. Figueiredo and Prof. Arne Thomas

      Version of Record online: 9 MAY 2011 | DOI: 10.1002/chem.201003025

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      Supporting chemistry! A reaction mechanism of aerobic oxidation of alcohols over activated-carbon-supported metal oxide catalysts was proposed (see scheme), in which the defects of the carbon support are major sites for oxygen adsorption and activation, whereas the metal oxide is responsible for alcohol adsorption and oxidation or dehydrogenation.

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      Version of Record online: 3 JUN 2011 | DOI: 10.1002/chem.201190128

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