Chemistry - A European Journal

Cover image for Vol. 18 Issue 8

February 20, 2012

Volume 18, Issue 8

Pages 2165–2447

  1. Cover Picture

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    3. Graphical Abstract
    4. News
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      Cover Picture: An Efficient Mixed-Ligand Pd Catalytic System to Promote C[BOND]N Coupling for the Synthesis of N-Arylaminotriazole Nucleosides (Chem. Eur. J. 8/2012) (page 2165)

      Yuting Fan, Dr. Yi Xia, Jingjie Tang, Dr. Fabio Ziarelli, Prof. Fanqi Qu, Dr. Palma Rocchi, Dr. Juan L. Iovanna and Dr. Ling Peng

      Article first published online: 10 FEB 2012 | DOI: 10.1002/chem.201290025

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      A mixed-ligand system of Pd/Synphos/Xantphos promotes effective C[BOND]N coupling in the synthesis of various N-arylaminotriazole and N-arylaminopurine nucleoside analogues. This catalytic system is strikingly powerful and efficient, allowing for unparalleled substrate scope and high product yields as well as promotion of C[BOND]Cl bond activation for C[BOND]N coupling. 31P NMR investigations provided useful evidence favoring a mechanism in which the catalytic reactions are mediated by ligand exchange during both Pd catalyst formation and oxidative insertion. For more details see the Communication by L. Peng et al. on page 2221 ff.

  2. Graphical Abstract

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    3. Graphical Abstract
    4. News
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  3. News

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  4. Concept

    1. Top of page
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    1. Energy Transfer

      Light-Harvesting Hybrid Assemblies (pages 2184–2194)

      K. Venkata Rao, Dr. K. K. R. Datta, Prof. Muthusamy Eswaramoorthy and Dr. Subi. J. George

      Article first published online: 31 JAN 2012 | DOI: 10.1002/chem.201103601

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      Glowing hybrids: An organic–inorganic approach has generated a variety of light-harvesting hybrid assemblies, with different physical nature based on their design (see scheme). These design concepts (covalent, semicovalent, and noncovalent approaches) are discussed with respect to the synthesis of artificial photosynthetic hybrids (MOF=metal–organic framework; PMO=periodic mesoporous organosilica).

  5. Communications

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    1. Cycloaddition Reactions

      Highly Diastereoselective Construction of Fused Carbocycles from Cyclopropane-1,1-dicarboxylates and Cyclic Enol Silyl Ethers: Scope, Mechanism, and Origin of Diastereoselectivity (pages 2196–2201)

      Dr. Jian-Ping Qu, Dr. Yong Liang, Hao Xu, Dr. Xiu-Li Sun, Prof. Dr. Zhi-Xiang Yu and Prof. Dr. Yong Tang

      Article first published online: 20 JAN 2012 | DOI: 10.1002/chem.201103495

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      Cyclopropane rings true: By selecting the appropriate substituents on the ester and silyl groups, fused cyclopentane derivatives with multiple contiguous stereocenters can be synthesized with excellent diastereoselectivity through CuII/bisoxazoline-catalyzed intermolecular [3+2] cycloaddition reactions of cyclopropane-1,1-dicarboxylates and cyclic enol silyl ethers (see scheme).

    2. Bioinorganic Chemistry

      Zwitterionic and Anionic Multinuclear Pentacoordinate Silicon(IV) Complexes with Bridging (R,R)-Tartrato(4−) Ligands and SiO5 Skeletons: Synthesis and Reactivity in Aqueous Solution (pages 2202–2206)

      Dr. Bastian Theis, Jörg Weiß, Dr. W. Peter Lippert, Dr. Rüdiger Bertermann, Dr. Christian Burschka and Prof. Dr. Reinhold Tacke

      Article first published online: 23 JAN 2012 | DOI: 10.1002/chem.201102815

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      Two nutrients in one molecule: A zwitterionic λ5Si,λ5Si′-disilicate (1) was synthesized and characterized. It contains ligands that exclusively derive from natural products ((R,R)-tartaric acid, choline). Hydrolysis of 1 yields 2, which shows a remarkable kinetic stability in water. Upon dissolution of 1 and 2 in water, the nutrients choline and orthosilicic acid are formed by hydrolysis

    3. Sensors

      Amplified Fluorescence Aptamer-Based Sensors Using Exonuclease III for the Regeneration of the Analyte (pages 2207–2211)

      Dr. Xiaoqing Liu, Ronit Freeman and Prof. Itamar Willner

      Article first published online: 25 JAN 2012 | DOI: 10.1002/chem.201103342

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      Quick and easy detection: The Exo III-stimulated regeneration of the analyte by the digestion of supramolecular aptamer–analyte complexes provides a means to develop amplified optical aptasensors (see figure).

    4. Metal-Free Diamination

      An Approach to the Regioselective Diamination of Conjugated Di- and Trienes (pages 2212–2216)

      Anton Lishchynskyi and Prof. Dr. Kilian Muñiz

      Article first published online: 25 JAN 2012 | DOI: 10.1002/chem.201103435

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      It's do or diaminate: The selective diamination of 1,3-butadienes in the presence of hypervalent iodine reagents has been developed. This oxidation process proceeds with complete selectivity in favor of diamination. Depending on the substrate, it proceeds either with 1,2- or 1,4-regioselectivity (see scheme).

    5. Higher Fullerenes

      X-ray Crystallographic Proof of the Isomer D2-C84(5) as Trifluoromethylated and Chlorinated Derivatives, C84(CF3)16, C84Cl20, and C84Cl32 (pages 2217–2220)

      Prof. Shangfeng Yang, Dr. Chuanbao Chen, Tao Wei, Dr. Nadezhda B. Tamm, Prof. Erhard Kemnitz and Prof. Sergey I. Troyanov

      Article first published online: 26 JAN 2012 | DOI: 10.1002/chem.201103456

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      Minor isomer comes forward: Minor isomer C84(5) has been captured by high temperature trifluoromethylation with CF3I and chlorination with VCl4. The compounds C84(CF3)16, C84Cl20, and C84(5)Cl32 were investigated by X-ray crystallography providing the first direct proof of the cage connectivity of D2-C84(5). The D2-C84(5)Cl32 molecule (see figure; C grey, Cl green) contains two flattened, pyrene-like substructures on opposite poles of the cage resulting in its drum-like shape.

    6. C[BOND]N Coupling

      An Efficient Mixed-Ligand Pd Catalytic System to Promote C[BOND]N Coupling for the Synthesis of N-Arylaminotriazole Nucleosides (pages 2221–2225)

      Yuting Fan, Dr. Yi Xia, Jingjie Tang, Dr. Fabio Ziarelli, Prof. Fanqi Qu, Dr. Palma Rocchi, Dr. Juan L. Iovanna and Dr. Ling Peng

      Article first published online: 20 JAN 2012 | DOI: 10.1002/chem.201103918

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      Make it unique! A mixed-ligand system of Pd/Synphos/Xantphos promotes effective C[BOND]N coupling in the synthesis of various N-arylaminotriazole and N-arylaminopurine nucleoside analogues. This catalytic system is strikingly powerful and efficient, allowing for unparalleled substrate scope and high product yields as well as promotion of C[BOND]Cl bond activation for C[BOND]N coupling (see scheme).

    7. Heterogeneous Catalysis

      Surface Oxygen-Assisted Pd Nanoparticle Catalysis for Selective Oxidation of Silanes to Silanols (pages 2226–2229)

      Dr. Ken-ichi Shimizu, Takahiro Kubo and Prof. Dr. Atsushi Satsuma

      Article first published online: 25 JAN 2012 | DOI: 10.1002/chem.201103088

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      Just add O2: Based on the fact that an oxygen-adsorbed Pd metal surface shows higher reactivity for water dissociation than a clean Pd surface, carbon-supported Pd nanoparticles (NPs) with surface oxygen atoms were developed as a highly effective and reusable heterogeneous catalyst for selective oxidation of silanes to silanols with water as a green oxidant (see figure).

    8. Total Synthesis

      Total Synthesis of Polyene Natural Product Dihydroxerulin by Mild Organocatalyzed Dehydrogenation of Alcohols (pages 2230–2234)

      Dr. Hexin Xie, Dr. Shilei Zhang, Prof. Dr. Hao Li, Xinshuai Zhang, Sihan Zhao, Zian Xu, Xixi Song, Prof. Dr. Xinhong Yu and Prof. Dr. Wei Wang

      Article first published online: 25 JAN 2012 | DOI: 10.1002/chem.201103325

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      Polyene synthesis: An efficient approach to the total synthesis of polyene natural product dihydroxrulin (1) is described. A novel, mild, direct organocatalytic IBX-mediated dehydrogenation process of simple alcohols to enals has been developed, which serves as a key step in the synthesis (see scheme).

    9. Nanoparticles

      Autonomous Self-Assembly of Ionic Nanoparticles into Hexagonally Close-Packed Lattices at a Planar Oil–Water Interface (pages 2235–2238)

      Dr. Volodymyr Sashuk, Prof. Robert Hołyst, Dr. Tomasz Wojciechowski, Prof. Ewa Górecka and Prof. Marcin Fiałkowski

      Article first published online: 26 JAN 2012 | DOI: 10.1002/chem.201103272

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      Let's get charged! Positively charged nanoparticles (NPs) spontaneously self-assemble into hexagonally close-packed lattices at a planar CH2Cl2–water interface (see figure). The self-assembly process is fully autonomous and occurs without any external manipulation.

    10. Macromolecules

      Synthesis, Electrochemical Properties and Self-Assembly of a Proton-Conducting Core–Shell Macromolecule (pages 2239–2243)

      Prof. Dr. Meizhen Yin, Naiwen Kang, Prof. Dr. Guanglei Cui, Dr. Zhihong Liu, Prof. Dr. Feng Wang, Prof. Dr. Wantai Yang, Dr. Markus Klapper and Prof. Dr. Klaus Müllen

      Article first published online: 26 JAN 2012 | DOI: 10.1002/chem.201103649

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      Let the protons flow: The synthesis of a core–shell macromolecule bearing phosphonic acids is presented. The rigid central core serves as a scaffold to stabilize the flexible polymer shells. Pronounced proton conductivity is obtained under humidified conditions. The self-assembly of such dendritic macromolecules by electrostatic interactions on a modified gold substrate is investigated and characterized.

  6. Full Papers

    1. Top of page
    2. Cover Picture
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
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    1. Supramolecular Co-polymers

      Photoreversible Supramolecular Polymerisation and Hierarchical Organization of Hydrogen-Bonded Supramolecular Co-polymers Composed of Diarylethenes and Oligothiophenes (pages 2244–2253)

      Prof. Dr. Shiki Yagai, Keisuke Ohta, Marina Gushiken, Kazunori Iwai, Atsushi Asano, Prof. Dr. Shu Seki, Dr. Yoshihiro Kikkawa, Prof. Dr. Masakazu Morimoto, Prof. Dr. Akihide Kitamura and Prof. Dr. Takashi Karatsu

      Article first published online: 31 JAN 2012 | DOI: 10.1002/chem.201103465

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      Designer photoresponsive assemblies: Oligothiophenes and diarylethenes are held together by multiple hydrogen bonds, affording photoresponsive and electroactive supramolecular copolymers. The co-polymer chains hierarchically organize into helical nanorods, which can be reversibly converted to small oligomeric species upon irradiation with UV and visible light (see figure).

    2. Ionic Liquids

      Synthesis and Characterization of Boranate Ionic Liquids (BILs) (pages 2254–2262)

      Dipl.-Chem. Mara Bürchner, Anna M. T. Erle, Dr. Harald Scherer and Prof. Dr. Ingo Krossing

      Article first published online: 20 JAN 2012 | DOI: 10.1002/chem.201102460

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      Boron goes liquid? The first syntheses of pure ionic liquids (ILs) with [BH4] and [B3H8] ions were realized as one-step reactions (see figure). These boranate ILs are suitable reagents for synthesis and have a potential for redox shuttling and storage/release of H2.

    3. Graphene

      Mixed Colloidal Suspensions of Reduced Graphene Oxide and Layered Metal Oxide Nanosheets: Useful Precursors for the Porous Nanocomposites and Hybrid Films of Graphene/Metal Oxide (pages 2263–2271)

      Yu Ri Lee, In Young Kim, Tae Woo Kim, Jang Mee Lee and Prof. Seong-Ju Hwang

      Article first published online: 17 JAN 2012 | DOI: 10.1002/chem.201102646

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      Mix masters: Mixed colloidal suspensions of reduced graphene oxide (RGO) and layered MnO2 nanosheets were synthesized (see figure) and applied as precursors for the synthesis of nanocomposites and hybrid films of RGO/MnO2.

    4. Nanostructures

      Growth Behavior and Kinetics of Self-Assembled Silica–Carbonate Biomorphs (pages 2272–2282)

      Dr. Matthias Kellermeier, Dr. Emilio Melero-García, Fabian Glaab, Josef Eiblmeier, Prof. Dr. Lorenz Kienle, Dr. Reinhard Rachel, Prof. Dr. Werner Kunz and Prof. Dr. Juan Manuel García-Ruiz

      Article first published online: 19 JAN 2012 | DOI: 10.1002/chem.201102407

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      Even spread: Precipitation of barium carbonate in silica-rich media at high pH yields hierarchically structured polycrystalline materials, termed silica–carbonate biomorphs, which exhibit complex curved shapes. Determination of microscopic growth rates and reagent concentration profiles (see figure) helped to elucidate the chemistry underlying the formation of these materials and provided insight into growth kinetics and morphogenetic aspects.

    5. Gas Sensing

      Controlled Synthesis and Enhanced Catalytic and Gas-Sensing Properties of Tin Dioxide Nanoparticles with Exposed High-Energy Facets (pages 2283–2289)

      Xue Wang, Xiguang Han, Shuifen Xie, Dr. Qin Kuang, Yaqi Jiang, Subing Zhang, Xiaoliang Mu, Guangxu Chen, Prof. Zhaoxiong Xie and Prof. Lansun Zheng

      Article first published online: 20 JAN 2012 | DOI: 10.1002/chem.201103280

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      New facets of SnO2: A morphology evolution of rutile SnO2 nanocrystals from low-energy facets to high-energy facets (see figure) is achieved in a basic environment. Our experimental results demonstrate that the catalytic activity of the crystal facets for CO oxidation follow the sequence {111}>{221}>{101}>{110}, whereas the gas-sensing properties of crystal surfaces is in order {221}>{111}≫{101}>{110}.

    6. Bifunctional Catalysts

      Polymer-Supported Enantioselective Bifunctional Catalysts for Nitro-Michael Addition of Ketones and Aldehydes (pages 2290–2296)

      Lital Tuchman-Shukron, Prof. Dr. Scott J. Miller and Prof. Dr. Moshe Portnoy

      Article first published online: 16 JAN 2012 | DOI: 10.1002/chem.201102474

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      “L” is right: Introduction of an L-amino acid spacer in a polymer-supported bifunctional catalyst, based on a chiral diamine, imparts outstanding activity and stereoselectivity in nitro-Michael addition, whereas D-amino acids are a poor match for the particular diamine configuration (see scheme). The reactivity patterns of the new catalysts shed light on the reaction mechanism and the C[BOND]C bond-forming transition state.

    7. Polyion Complex Micelles

      Synthesis of Thermo- and pH-Sensitive Polyion Complex Micelles for Fluorescent Imaging (pages 2297–2304)

      Yun Liu, Cao Li, Dr. Hui-Yuan Wang, Prof. Dr. Xian-Zheng Zhang and Prof. Ren-Xi Zhuo

      Article first published online: 16 JAN 2012 | DOI: 10.1002/chem.201102704

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      Responsive polyions! Two oppositely charged polypeptide-based copolymers have been successfully synthesized. A mixture of these copolymers in aqueous solution led to PIC micelles that exhibit thermo- and pH-sensitivity. The PIC micelles were fluorescently labeled with Rhodamine B and 5-aminofluorescein to give novel multicolored PIC micelles, the fluorescence properties of which could be controlled by variation of the temperature or pH (see figure).

    8. Tungsten Oxide Nanoparticles

      Study of the Chemical Mechanism Involved in the Formation of Tungstite in Benzyl Alcohol by the Advanced QEXAFS Technique (pages 2305–2312)

      Inga Olliges-Stadler, Jan Stötzel, Dr. Dorota Koziej, Dr. Marta D. Rossell, Prof. Dr. Jan-Dierk Grunwaldt, Dr. Maarten Nachtegaal, Prof. Dr. Ronald Frahm and Prof. Dr. Markus Niederberger

      Article first published online: 16 JAN 2012 | DOI: 10.1002/chem.201101514

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      Complex chemistry! The mechanism for the formation of tungstite nanoparticles (see figure) has been investigated by time-dependent gas chromatography and X-ray diffraction as well as by time-resolved in situ X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy.

    9. Gold Catalysis

      Dual-Function of Alcohols in Gold-Mediated Selective Coupling of Amines and Alcohols (pages 2313–2318)

      Dr. Bingjun Xu, Prof. Robert J. Madix and Prof. Cynthia M. Friend

      Article first published online: 17 JAN 2012 | DOI: 10.1002/chem.201103232

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      Complete selectivity switch from dehydrogenation to oxidative-coupling of alcohol and dimethylamine to form the corresponding amide on atomic-oxygen-activated Au(111) is reached through the efficient removal of the excess atomic oxygen by molecularly adsorbed alcohol (see scheme).

    10. Ligand Effects

      Ligand-Modification Effects on the Reactivity, Solubility, and Stability of Organometallic Tantalum Complexes in Water (pages 2319–2326)

      Dr. Ana Conde, Dr. Rosa Fandos, Dr. Carolina Hernández, Prof. Dr. Antonio Otero, Dr. Ana Rodríguez and Dr. María José Ruiz

      Article first published online: 20 JAN 2012 | DOI: 10.1002/chem.201103026

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      Ta Ta for now: C[BOND]C coupling processes on a tantalum-bound pincer ligand give rise to a series of tantalum derivatives with a variety of tetradentate ligands (see figure). The role of the ligand substituents on the reactivity and properties of the corresponding complexes is discussed.

    11. Bridging Ligands

      Monohaloboryls (BHX) as Bridging Ligands: Observable Dinuclear σ-(Halo)boranyl Intermediates in the Synthesis of Metalloborylenes (pages 2327–2334)

      Jürgen Bauer, Prof. Dr. Holger Braunschweig, Dr. Rian D. Dewhurst, Dr. Katharina Kraft and Dr. Krzysztof Radacki

      Article first published online: 20 JAN 2012 | DOI: 10.1002/chem.201103163

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      Monohaloboryl ligands: Reaction of transition-metal–dihaloboryl complexes of the form [LnMBX2] with K[(η5-C5H5)MnH(CO)2], leads, via salt elimination, migration of the Mn-bound hydride onto the B atom, and loss of HX, to the formation of metalloborylenes.

    12. Nanostructures

      Controlled Synthesis of Uniform and Monodisperse Upconversion Core/Mesoporous Silica Shell Nanocomposites for Bimodal Imaging (pages 2335–2341)

      Jianan Liu, Prof. Wenbo Bu, Shengjian Zhang, Feng Chen, Huaiyong Xing, Limin Pan, Prof. Liangping Zhou, Prof. Weijun Peng and Prof. Jianlin Shi

      Article first published online: 17 JAN 2012 | DOI: 10.1002/chem.201102599

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      Movin' on up: Uniform and monodisperse upconversion core/mesoporous silica shell structured nanocomposites of sub-50 nm diameter were successfully synthesized (see figure). Multifunctional bioapplications of the synthesized nanocomposite particles for simultaneous magnetic resonance and upconversion fluorescence imaging are presented.

    13. Natural Products

      Determination of the Absolute Configuration of Peptide Natural Products by Using Stable Isotope Labeling and Mass Spectrometry (pages 2342–2348)

      Prof. Dr. Helge B. Bode, Daniela Reimer, Dipl.-Biol. Sebastian W. Fuchs, Ferdinand Kirchner, Dipl.-Chem. Christina Dauth, Dr. Carsten Kegler, Dipl.-Pharm. Wolfram Lorenzen, Dr. Alexander O. Brachmann and Peter Grün

      Article first published online: 20 JAN 2012 | DOI: 10.1002/chem.201103479

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      Game over—structure solved: A combination of labeling experiments with mass spectrometry results in the reliable determination of the sum formula, the nature of the building blocks, and (for peptide natural products) also the determination of the absolute configuration as exemplified for the novel natural products GameXPeptide A–D (see scheme).

    14. Zinc Complexes

      Coordination Chemistry and Reactivity of Zinc Complexes Supported by a Phosphido Pincer Ligand (pages 2349–2360)

      Dr. Ilaria D'Auria, Dr. Marina Lamberti, Dr. Mina Mazzeo, Dr. Stefano Milione, Dr. Giuseppina Roviello and Prof. Dr. Claudio Pellecchia

      Article first published online: 20 JAN 2012 | DOI: 10.1002/chem.201102414

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      A state of flux: Diarylphosphido diphosphine zinc complexes show fluxional behavior and efficiently promote the ring-opening polymerization (ROP) of ε-caprolactone (CL) and L- and rac-lactide (LA), as well as copolymerization of CL and LA, under mild conditions to give polyCL (PCL), PLA, and CL–LA copolymers, respectively (see scheme).

    15. Dendrimers

      Supramolecular Dendrimers: Convenient Synthesis by Programmed Self-Assembly and Tunable Thermoresponsivity (pages 2361–2365)

      Dr. Partha S. Ghosh and Prof. Dr. Andrew D. Hamilton

      Article first published online: 20 JAN 2012 | DOI: 10.1002/chem.201103051

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      Treescape: The tetrameric assembly of dendrons through G-quadruplex formation (see figure) is reported. The dynamic character of the self-assembly process can be exploited to create dendrimers with thermoresponsive behavior that can be tuned over a wide temperature range. The approach also promises access to many different dendrimers by using the combination of varied components.

    16. Chirality Transfer

      Supermolecular Chiral Mesogenic Tripedes (pages 2366–2373)

      Dr. Abdelhak Belaissaoui, Dr. Isabel M. Saez, Dr. Stephen J. Cowling, Dr. Xiangbing Zeng and Prof. John W. Goodby

      Article first published online: 19 JAN 2012 | DOI: 10.1002/chem.201102193

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      The mesogenic behaviours of six tripedes based around two stereogenic cores were investigated. The major result concerns the transfer of the chiral information from the central core to the periphery and the effect on mesomorphic properties. These properties were fine-tuned by incorporating functional moieties within the chiral core without modifying its stereogenicity.

    17. Artificial Photosynthesis

      Catalytic Four-Electron Oxidation of Water by Intramolecular Coupling of the Oxo Ligands of a Bis(ruthenium–bipyridine) Complex (pages 2374–2381)

      Prof. Dr. Tohru Wada, Dr. Hideki Ohtsu and Prof. Dr. Koji Tanaka

      Article first published online: 16 JAN 2012 | DOI: 10.1002/chem.201102236

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      Forming an O[BOND]O bond: The bis(ruthenium–bipyridine) complex [Ru2(μ-Cl)(bpy)2(btpyan)](BF4)3 ([1](BF4)3; bpy=2,2′-bipyridine, btpyan=1,8-bis(2,2′:6′,2′′-terpyrid-4′-yl)anthracene; see the scheme) catalyzes the chemical and electrochemical oxidation of water. Resonance Raman spectroscopic measurements of the oxidized form of the [1]3+ ion revealed the formation of a [Ru2(bpy)2(btpyan)(μ-O2)]4+ ion through the intramolecular coupling of two RuIV[DOUBLE BOND]O units.

    18. Electrocyclic Reactions

      One-Pot Organocatalytic Tandem Aldol/Polycyclization Reactions between 1,3-Dicarbonyl Compounds and α,β,γ,δ-Unsaturated Aldehydes for the Straightforward Assembly of Cyclopenta[b]furan-Type Derivatives: New Insight into the Knoevenagel Reaction (pages 2382–2388)

      Martín J. Riveira and Dr. Mirta P. Mischne

      Article first published online: 16 JAN 2012 | DOI: 10.1002/chem.201103080

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      Exceed the limits! Cyclopenta[b]dihydrofuran derivatives are easily accessed through a one-pot Knoevenagel-initiated cascade approach (see scheme; EDDA=ethylenediammonium diacetate) by starting from simple precursors. A new type of carbonyl polyene system that displays unprecedented reactivity has been established.

    19. Self-Assembling Capsules

      Novel Capsular Aggregates from Flexible Tripodal Triureas with Cs Symmetry (pages 2389–2397)

      Prof. Dr. Mateo Alajarin, Dr. Raul-Angel Orenes, Prof. Dr. Judith A. K. Howard, Dr. Elinor C. Spencer, Prof. Dr. Jonathan W. Steed and Dr. Aurelia Pastor

      Article first published online: 19 JAN 2012 | DOI: 10.1002/chem.201102246

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      Contortionist molecules: Flexible tris(2- and 3-ureidobenzyl)amines with Cs symmetry self-assemble to give mixtures of regioisomeric capsular aggregates (see figure). Of special significance is the efficient self-assembly of a more flexible triurea endowed with a ureidopropylic arm.

    20. Asymmetric Catalysis

      Isothiourea-Mediated Asymmetric O- to C-Carboxyl Transfer of Oxazolyl Carbonates: Structure–Selectivity Profiles and Mechanistic Studies (pages 2398–2408)

      Caroline Joannesse, Craig P. Johnston, Louis C. Morrill, Philip A. Woods, Madeleine Kieffer, Dipl.-Chem. Tobias A. Nigst, Prof. Herbert Mayr, Dr. Tomas Lebl, Prof. Douglas Philp, Dr. Ryan A. Bragg and Dr. Andrew D. Smith

      Article first published online: 19 JAN 2012 | DOI: 10.1002/chem.201102847

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      As easy as O to C: The ability of a series of tetrahydropyrimidine-based isothioureas to promote the asymmetric Steglich reaction has been evaluated (see scheme). Good to excellent levels of enantioselectivity were generally observed for the rearrangement of oxazolyl carbonates, with markedly different catalytic efficiencies observed with variation of the stereodirecting group(s). Crossover and dynamic 19F NMR experiments were also used to develop a mechanistic understanding of this transformation.

    21. Supramolecular Chemistry

      Template Effects in SN2 Displacements for the Preparation of Pseudopeptidic Macrocycles (pages 2409–2422)

      Vicente Martí-Centelles, Prof. Dr. M. Isabel Burguete and Prof. Dr. Santiago V. Luis

      Article first published online: 19 JAN 2012 | DOI: 10.1002/chem.201101416

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      Closing the ring: Appropriate anions can act as specific kinetic templates for the ring-closing step in macrocyclisation reactions of pseudopeptides, through supramolecular interactions at the transition state (see figure).

    22. Iron Catalysis

      Fe-Catalyzed Multicomponent Reactions: The Regioselective Alkoxy Allylation of Activated Olefins and its Application in Sequential Fe Catalysis (pages 2423–2429)

      Dipl.-Chem. Dipl.-Ing. André P. Dieskau, Dipl.-Chem. Michael S. Holzwarth and Prof. Dr. Bernd Plietker

      Article first published online: 16 JAN 2012 | DOI: 10.1002/chem.201103009

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      Iron adds it: Allylic carbonates react with various activated olefins in an Fe-catalyzed decarboxylative alkoxy allylation to afford densely substituted products in good yields and with high regioselectivities under mild conditions (see scheme). The robustness of the catalytic system is demonstrated by the first Fe-catalyzed alkoxy allylation allylic sulfenylation and three-component coupling sequence.

    23. Helical Structures

      One-Handed Helical Screw Direction of Homopeptide Foldamer Exclusively Induced by Cyclic α-Amino Acid Side-Chain Chiral Centers (pages 2430–2439)

      Dr. Yosuke Demizu, Prof. Mitsunobu Doi, Dr. Masaaki Kurihara, Prof. Tokumi Maruyama, Prof. Hiroshi Suemune and Prof. Masakazu Tanaka

      Article first published online: 20 JAN 2012 | DOI: 10.1002/chem.201102902

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      Twist to the left: The left-handed (M) 310 and α helices of (3S,4S)-1-amino-3,4-(dialkoxy)cyclopentanecarboxylic acid (R: methyl or methoxymethyl) homochiral homopeptides (see structure of methyl decapeptide; Cbz: benzyloxycarbonyl) are exclusively controlled by the side-chain chiral centers, because the cyclic amino acid does not have an α-carbon chiral center but has side-chain γ-carbon chiral centers (see figure). The oligopeptides can be well dissolved in pure water and are more α helical in water than in 2,2,2-trifluoroethanol solution.

    24. Asymmetric Catalysis

      Enantioselective Zinc/BINOL-Catalysed Alkynylation of Aldimines Generated in Situ from α-Amido Sulfones (pages 2440–2444)

      Dr. Gonzalo Blay, Ana Brines, Alicia Monleón and Prof. Dr. José R. Pedro

      Article first published online: 19 JAN 2012 | DOI: 10.1002/chem.201102909

      Thumbnail image of graphical abstract

      Chiral nonracemic propargylic amines with Cbz protection (see scheme) have been prepared by the addition of terminal alkynes to imines generated in situ from α-amido sulfones in the presence of diethylzinc and BINOL-type ligands as catalysts. The reactions give good yields and high enantioselectivities (ee values up to 95 %) for a good number of aromatic and heteroaromatic α-amido sulfones and alkynes.

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      Preview: Chem. Eur. J. 9/2012 (page 2447)

      Article first published online: 10 FEB 2012 | DOI: 10.1002/chem.201290028

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