Chemistry - A European Journal

Cover image for Vol. 19 Issue 15

April 8, 2013

Volume 19, Issue 15

Pages 4645–4950

  1. Cover Pictures

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Correspondence
    1. You have free access to this content
      Cover Picture: Manipulating Catalytic Pathways: Deoxygenation of Palmitic Acid on Multifunctional Catalysts (Chem. Eur. J. 15/2013) (page 4645)

      Dr. Baoxiang Peng, Dr. Chen Zhao, Stanislav Kasakov, Sebastian Foraita and Prof. Dr. Johannes A. Lercher

      Version of Record online: 3 APR 2013 | DOI: 10.1002/chem.201390049

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      Microalgae to green diesel oils The mechanism of the catalytic reduction of palmitic acid to n-pentadecane at 260 °C in the presence of hydrogen over catalysts combining multiple functions has been explored by C. Zhao, J. A. Lercher, et al. in their Full Paper on page 4732 ff. A new redundancy catalysis route has been established on the surface of Ni/ZrO2 in the cascade hydrodeoxygenation reaction.

    2. You have free access to this content
      Back Cover: Biotemplated Hierarchical Porous Material: The Positively Charged Leaf (Chem. Eur. J. 15/2013) (page 4952)

      Dr. Dalong Yang, Prof. Dr. Tongxiang Fan, Prof. Dr. Di Zhang, Dr. Jun Zhu, Yun Wang, Dr. Bin Du and Prof. Dr. Yaxian Yan

      Version of Record online: 3 APR 2013 | DOI: 10.1002/chem.201390052

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      A positively charged leaf was synthesized by a simple, facile chemical method and the material shows the advantages of a hierarchical porous structure, nanoscale size, positively charged property, and sterilization effect that could be utilized for water purification for the removal of dyes and pollutants, especially for efficient Escherichia coli removal. The synthesis method for the positively charged leaf could be applied to the synthesis of different kinds of functional metal oxides. For more details, see the Full Paper by T. Fan et al. on page 4742 ff.

  2. Graphical Abstract

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Correspondence
  3. News

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Correspondence
  4. Concept

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Correspondence
    1. Organocatalysis

      Catalysis with N-Heterocyclic Carbenes under Oxidative Conditions (pages 4664–4678)

      Dr. Suman De Sarkar, Anup Biswas, Ramesh C. Samanta and Prof. Dr. Armido Studer

      Version of Record online: 21 FEB 2013 | DOI: 10.1002/chem.201203707

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      Cascading down: Reaction of an aldehyde with an NHC provides the corresponding Breslow intermediate A, which can be readily oxidized with various organic and inorganic oxidants to give the acylazolium ion B (see scheme). Intermediate B can react with various nucleophiles either at the 2 or 4-position. With enals as starting aldehydes, elegant cascade processes have been developed using oxidative carbene catalysis.

  5. Communications

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Correspondence
    1. Anion Recognition

      Anion-Driven Reversible Switching of Metal-Centered Stereoisomers in Metallopeptides (pages 4680–4685)

      Dr. Naoki Ousaka, Yuki Takeyama and Prof. Dr. Eiji Yashima

      Version of Record online: 11 MAR 2013 | DOI: 10.1002/chem.201300361

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      Anion-triggered chiral switch: Reversible switching between fac and mer isomers in tris(2,2′-bipyridine)iron(II) complexes, the ligands of which are substituted at the 5-position with various peptides of different lengths and sequences, has been achieved (see figure). The remote stereocontrol at the FeII center by a domino-type chiral information transfer along an achiral peptide main-chain was observed even over 3 nm (50 bond lengths).

    2. Homologation

      Lewis Acid Catalyzed Enlargement of Cyclic β-Alkoxyenals and One-Pot Synthesis of Polyfunctional Enoxysilanes Derived from Aucubin with Trimethylsilyldiazomethane (pages 4686–4690)

      Dr. Christelle Lemus, Dr. Marko Poleschak, Sophie Gailly, Dr. Marine Desage-El Murr, Prof. Michel Koch and Prof. Brigitte Deguin

      Version of Record online: 28 FEB 2013 | DOI: 10.1002/chem.201203968

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      Pyrane to oxepane in one step: Highly regio- and stereoselective homologations dependent on the nature of carbonyl function and catalysts have been observed during the formation of enoxysilanes (see scheme). Trimethylsilyl trifluoromethanesulfonate (TMSOTf) and AlCl3 were identified as suitable catalysts to promote the homologation and ring-enlargement.

    3. Asymmetric Synthesis

      Development of Metal/Organo Catalytic Systems for Direct Vinylogous Michael Reactions to Build Chiral γ,γ-Disubstituted Butenolides (pages 4691–4694)

      Dongxu Yang, Linqing Wang, Dr. Depeng Zhao, Fengxia Han, Dr. Bangzhi Zhang and Prof. Dr. Rui Wang

      Version of Record online: 4 MAR 2013 | DOI: 10.1002/chem.201204466

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      Vinylogous reactions: The direct asymmetric vinylogous conjugate additions of γ-aryl- and alkyl-substituted butenolides to enones was realized for the first time by a designed and tested metal/organo dual-activation strategy, in which two effective metal/organo cooperative catalytic systems have been built (see scheme).

    4. Diels–Alder reaction

      Gold-Catalyzed Reactions of Enynals/Enynones with Norbornenes: Generation and Trapping of Cyclic o-Quinodimethanes (o-QDMs) (pages 4695–4700)

      Prof. Dr. Shifa Zhu, Zhicai Zhang, Xiaobing Huang, Prof. Dr. Huanfeng Jiang and Zhengjiang Guo

      Version of Record online: 4 MAR 2013 | DOI: 10.1002/chem.201300232

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      Fan-like structures: An efficient AuIII-catalyzed method to generate the highly reactive cyclic o-quinodimethane (o-QDM) species from easily available enynals or enynones is presented (see scheme). This method produced a variety of structurally unique fan-like products with the advantages of mild reaction conditions, excellent diastereoselectivities, and high functional-group tolerance.

    5. Annulation

      Rhodium(III)-Catalyzed Amidation of Aryl Ketone O-Methyl Oximes with Isocyanates by C[BOND]H Activation: Convergent Synthesis of 3-Methyleneisoindolin-1-ones (pages 4701–4706)

      Dr. Bing Zhou, Dr. Wei Hou, Dr. Yaxi Yang and Prof. Dr. Yuanchao Li

      Version of Record online: 4 MAR 2013 | DOI: 10.1002/chem.201204448

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      Going green! The rhodium(III)-catalyzed annulation of aryl ketone O-methyl oximes with isocyanates for the synthesis of 3-methyleneisoindolin-1-ones is reported (see scheme). This reaction exhibits high regioselectivity, functional-group tolerance, and broad substrate scope, without the use of additives or production of environmentally hazardous waste.

    6. Metal–Metal Interactions

      Connecting C[TRIPLE BOND]C Bonds to Tetrairidium Chains (pages 4707–4711)

      Dr. M. Pilar del Río, Dr. José A. López, Prof. Dr. Miguel A. Ciriano and Dr. Cristina Tejel

      Version of Record online: 28 FEB 2013 | DOI: 10.1002/chem.201203769

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      The chain gang! Tetrametallic iridium chains with the metal atoms in an average oxidation state 1.5 and bound by unsupported metal–metal bonds have been effectively connected to organic fragments with delocalized π electrons, such as 1,4-diethynylbenzene (see figure). This connection allows an electronic communication along the whole chain spanning around 30 Å and sheds light on the possible use of this type of molecule as “molecular wires”.

    7. Reaction Mechanisms

      Synergistic Empirical and Theoretical Study on the Stereoselective Mechanism for the Aluminum Salalen Complex Mediated Polymerization of rac-Lactide (pages 4712–4716)

      Ines dos Santos Vieira, Dr. Emma L. Whitelaw, Dr. Matthew D. Jones and Prof. Dr. Sonja Herres-Pawlis

      Version of Record online: 28 FEB 2013 | DOI: 10.1002/chem.201203973

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      Open your ring: Aluminum salalen complexes are used to initiate the ring-opening polymerization (ROP) of rac-lactide (LA). The reaction pathway of the LA isomers was elucidated by a detailed computational study, which revealed that small changes in the catalytic “bag” implicate the change in induced tacticity (see scheme; PLA= polylactide).

    8. Fluorescent Probes

      A Ratiometric Fluorescent Probe for Biological Signaling Molecule H2S: Fast Response and High Selectivity (pages 4717–4722)

      Jing Liu, Yuan-Qiang Sun, Jingyu Zhang, Ting Yang, Jianbin Cao, Lishen Zhang and Prof. Dr. Wei Guo

      Version of Record online: 4 MAR 2013 | DOI: 10.1002/chem.201300455

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      Selective and fast: A flavylium derivative-based ratiometric fluorescent probe (1) for H2S is reported. The reaction mechanism (see scheme) is based on the nucleophilic addition of H2S towards the electrically positive benzopyrylium moiety of 1, which can efficiently differentiate H2S from other competitive species. The probe exhibits a fast response toward H2S, within 10 s, which is superior to most of the reported H2S probes.

  6. Full Papers

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Correspondence
    1. Reaction Mechanisms

      Hydroxypalladation Precedes the Rate-Determining Step in the Wacker Oxidation of Ethene (pages 4724–4731)

      Venkataramana Imandi, Sooraj Kunnikuruvan and Dr. Nisanth N. Nair

      Version of Record online: 13 MAR 2013 | DOI: 10.1002/chem.201204342

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      Isomerization matters: Isomerization, involving a cis-to-trans ligand rotation, is the rate-determining step in the Wacker oxidation of ethene. Ab initio molecular-dynamics simulations explore the full mechanism and kinetics of this reaction (see figure).

    2. Biomass

      Manipulating Catalytic Pathways: Deoxygenation of Palmitic Acid on Multifunctional Catalysts (pages 4732–4741)

      Dr. Baoxiang Peng, Dr. Chen Zhao, Stanislav Kasakov, Sebastian Foraita and Prof. Dr. Johannes A. Lercher

      Version of Record online: 20 MAR 2013 | DOI: 10.1002/chem.201203110

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      Biomass to biofuels: The conversion of palmitic acid to n-pentadecane over ZrO2 mainly proceeds by hydrogenation of the carboxylic acid group to give hexadecanal (rate-determining step), which is catalyzed either solely by Ni sites or synergistically by Ni sites and sites on the ZrO2 support (see scheme). In the absence of H2, ketonization is the dominant reaction catalyzed by ZrO2.

    3. Biomaterials

      Biotemplated Hierarchical Porous Material: The Positively Charged Leaf (pages 4742–4747)

      Dr. Dalong Yang, Prof. Dr. Tongxiang Fan, Prof. Dr. Di Zhang, Dr. Jun Zhu, Yun Wang, Dr. Bin Du and Prof. Dr. Yaxian Yan

      Version of Record online: 7 MAR 2013 | DOI: 10.1002/chem.201300266

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      Leaf shield: A hierarchical porous, positively charged material was synthesized from a leaf biotemplate (see graphic). The final product inherited the advantages of a positively charged property, hierarchical porous structure and sterilization effect. The product, like a leaf shield, could be used to protect against bacteria.

    4. Graphene

      Precise Tuning of Surface Composition and Electron-Transfer Properties of Graphene Oxide Films through Electroreduction (pages 4748–4753)

      Dr. Adriano Ambrosi and Prof. Martin Pumera

      Version of Record online: 21 FEB 2013 | DOI: 10.1002/chem.201204226

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      Film studies: Electrochemical reduction allows for precise tuning of the surface composition of graphene oxide films by altering the content of the oxygen functionalities (see figure). The electrochemical activity of graphene oxide modified electrodes can therefore be adjusted to specific levels according to the desired application.

    5. Metal–Metal Interactions

      Experimental and Theoretical Evidence of the Existence of Gold(I)⋅⋅⋅Mercury(II) Interactions in Solution through Fluorescence-Quenching Measurements (pages 4754–4766)

      Dr. Tania Lasanta, Prof. Dr. José M. López-de-Luzuriaga, Dr. Miguel Monge, Dr. M. Elena Olmos and David Pascual

      Version of Record online: 21 FEB 2013 | DOI: 10.1002/chem.201203789

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      Goldeneye: Complexes of the type{[Hg(R)2][Au(R′)(PMe3)]2}n (R and R′=perhalophenyl groups), with metallophilic AuI⋅⋅⋅HgII interactions, were detected in solution by quenching experiments of arenes, which were reproduced at the theoretical level (see scheme).

    6. Host–Guest Chemistry

      The Entrapment of Chiral Guests with Gated Baskets: Can a Kinetic Discrimination of Enantiomers Be Governed through Gating? (pages 4767–4775)

      Dr. Bao-Yu Wang, Sandra Stojanović, Daniel A. Turner, Tanya L. Young, Prof. Christopher M. Hadad and Prof. Jovica D. Badjić

      Version of Record online: 21 FEB 2013 | DOI: 10.1002/chem.201204344

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      Falling into a trap: Controlling the rate at which two stereoisomeric compounds enter a host presents a challenge. Gated molecular baskets (see figure) are shown to be excellent prototypes for implementing a kinetic differentiation of guests.

    7. Oligosaccharides

      Three-Dimensional Arrays Using GlycoPEG Tags: Glycan Synthesis, Purification and Immobilisation (pages 4776–4785)

      Dr. Juan Etxebarria, Dr. Sonia Serna, Dr. Ana Beloqui, Prof. Dr. Manuel Martin-Lomas and Dr. Niels-Christian Reichardt

      Version of Record online: 11 FEB 2013 | DOI: 10.1002/chem.201204004

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      Got you PEGged: A polyethyleneglycol (PEG)-tag-based approach has been developed that accelerates the preparation of glycan arrays and glyco beads on all levels by improving the chemo-enzymatic synthesis, the purification and immobilisation of oligosaccharides (see figure).

    8. NMR Spectroscopy

      Selective Targeting of Dendritic Cell-Specific Intercellular Adhesion Molecule-3-Grabbing Nonintegrin (DC-SIGN) with Mannose-Based Glycomimetics: Synthesis and Interaction Studies of Bis(benzylamide) Derivatives of a Pseudomannobioside (pages 4786–4797)

      Norbert Varga, Ieva Sutkeviciute, Cinzia Guzzi, John McGeagh, Isabelle Petit-Haertlein, Serena Gugliotta, Jörg Weiser, Jesús Angulo, Franck Fieschi and Anna Bernardi

      Version of Record online: 18 FEB 2013 | DOI: 10.1002/chem.201202764

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      Receptor targeting: For the first time glycomimetics based on a mannose anchor have been tuned to selectively inhibit DC-SIGN (dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin) over Langerin. Based on structural and binding studies of a mannobioside mimic previously described, a focused library of derivatives was designed (see figure).

    9. Phosphorescence

      Vaulted trans-Bis(salicylaldiminato)platinum(II) Crystals: Heat-Resistant, Chromatically Sensitive Platforms for Solid-State Phosphorescence at Ambient Temperature (pages 4798–4811)

      Dr. Naruyoshi Komiya, Dr. Minoru Okada, Kanako Fukumoto, Kenji Kaneta, Atsushi Yoshida and Prof. Takeshi Naota

      Version of Record online: 18 FEB 2013 | DOI: 10.1002/chem.201203669

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      Tuning it in: Strong phosphorescent emission is observed for a variety of crystalline polymethylene- and polyoxyethylene-bridged trans-bis(salicylaldiminato)platinum(II) complexes (see figure). The heat resistance and color of the solid-state emission can be controlled by tuning the molecular array and electronic configuration of the vaulted complexes by altering linkers and substituents.

    10. Drug Delivery

      Multifunctional Core-Shell-Corona-Type Polymeric Micelles for Anticancer Drug-Delivery and Imaging (pages 4812–4817)

      Dr. Bishnu Prasad Bastakoti, Prof. Kevin C.-W. Wu, Dr. Masamichi Inoue, Prof. Shin-ichi Yusa, Prof. Kenichi Nakashima and Prof. Yusuke Yamauchi

      Version of Record online: 18 FEB 2013 | DOI: 10.1002/chem.201203958

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      Sustained strategy delivers: A facile strategy for fabricating multifunctional polymeric micelles for anticancer drug-delivery and imaging is presented (see figure). Cisplatin can be incorporated into the shell of polymeric micelles that have an imaging agent already encapsulated for visualizing the pH-triggered drug release. The neutral and hydrophilic corona sterically stabilizes the multifunctional polymeric micelles in aqueous solution for long-term circulation in the human body.

    11. Heterocycle Synthesis

      Synthesis of 2,2,5,5-Tetrasubstituted 1,4-Dioxa-2,5-disilacyclohexanes via Organotin(IV)-Catalyzed Transesterification of (Acetoxymethyl)alkoxysilanes (pages 4818–4825)

      Dipl.-Chem. Sascha A. Erhardt, Dr. Florian Hoffmann, Dr. Jürgen O. Daiß, Dr. Jürgen Stohrer, Dr. Eberhardt Herdtweck and Prof. Dr. Bernhard Rieger

      Version of Record online: 18 FEB 2013 | DOI: 10.1002/chem.201202124

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      Tin makes the ring! Easily accessible (acetoxymethyl)silanes with at least one alkoxy group give 2,2,5,5-organo-substituted 1,4-dioxa-2,5-disilacyclohexanes (see figure) in good yields and high purity when treated with organotin(IV) catalysts. The mild reaction conditions even allowed the synthesis of cyclic silanes with hydrolytically labile alkoxy substituents.

    12. Self-Assembly

      Design of Stable β-Sheet-Based Cyclic Peptide Assemblies Assisted by Metal Coordination: Selective Homo- and Heterodimer Formation (pages 4826–4834)

      Michele Panciera, Prof. Dr. Manuel Amorín, Prof. Dr. Luis Castedo and Prof. Dr. Juan R. Granja

      Version of Record online: 19 FEB 2013 | DOI: 10.1002/chem.201203213

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      Metal tweezers: The self-assembling properties of α,γ-cyclic peptides are reinforced by metal coordination to precisely construct homo- and heterodimeric complexes. The metal coordination is able to shift the equilibrium from several nonequivalent dimers to one single ensemble (see scheme).

    13. Synthetic Methods

      Reagent Control of [1,2]-Wagner–Meerwein Shift Chemoselectivity Following the Nazarov Cyclization: Application to the Total Synthesis of Enokipodin B (pages 4835–4841)

      Dr. David Lebœuf, Christopher M. Wright and Prof. Alison J. Frontier

      Version of Record online: 21 FEB 2013 | DOI: 10.1002/chem.201203395

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      Total control: A rapid and convergent access to the skeleton of selected cuparane and herbertane sesquiterpenes was developed by using a copper(II)-promoted Nazarov cyclization/Wagner–Meerwein rearrangement sequence as the key step. This methodology was then employed to achieve the concise total synthesis of enokipodin B (see scheme).

    14. Efficient Nazarov Cyclization/Wagner–Meerwein Rearrangement Terminated by a CuII-Promoted Oxidation: Synthesis of 4-Alkylidene Cyclopentenones (pages 4842–4848)

      Dr. David Lebœuf, Eric Theiste, Prof. Vincent Gandon, Stephanie L. Daifuku, Prof. Michael L. Neidig and Prof. Alison J. Frontier

      Version of Record online: 21 FEB 2013 | DOI: 10.1002/chem.201203396

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      The ultimate sequence: A series of 1,4-dien-3-ones were subjected to copper(II) complexes (1 equiv) under an air atmosphere to provide access to 4-alkylidene cyclopentenones through an original Nazarov cyclization/Wagner–Meerwein rearrangement/oxidation/elimination sequence (see scheme).

    15. Natural Products

      New Synthesis of A-Ring Aromatic Strigolactone Analogues and Their Evaluation as Plant Hormones in Pea (Pisum sativum) (pages 4849–4857)

      Dr. Victor X. Chen, Dr. François-Didier Boyer, Dr. Catherine Rameau, Jean-Paul Pillot, Dr. Jean-Pierre Vors and Prof. Jean-Marie Beau

      Version of Record online: 18 FEB 2013 | DOI: 10.1002/chem.201203585

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      Inhibiting shoot branching: A new general access to A-ring aromatic strigolactones (see scheme), a new class of plant hormones, has been developed. The biological activity of various analogues synthesized by this strategy for inhibiting bud outgrowth in pea was evaluated.

    16. Homogeneous Catalysis

      Mechanistic Studies on the SCS-Pincer Palladium(II)-Catalyzed Tandem Stannylation/Electrophilic Allylic Substitution of Allyl Chlorides with Hexamethylditin and Benzaldehydes (pages 4858–4868)

      Dr. Niels J. M. Pijnenburg, Dr. Yves H. M. Cabon, Prof. Dr. Gerard van Koten and Prof. Dr. Robertus J. M. Klein Gebbink

      Version of Record online: 21 FEB 2013 | DOI: 10.1002/chem.201203049

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      Minor isomer, major importance: A mechanistic study of the SCS-pincer Pd-catalyzed auto-tandem reaction is described consisting of the stannylation of cinnamyl chloride, followed by an electrophilic allylic substitution of the primary tandem reaction product to yield homoallylic alcohols (see scheme; SCS=[2,6-(CH2SPh)2C6H3]). This study pointed out that the anticipated stannylation product, cinnamyl trimethylstannane, is not a substrate for the second part of the tandem reaction.

    17. Hybrid Materials

      Aripiprazole[BOND]Montmorillonite: A New Organic–Inorganic Nanohybrid Material for Biomedical Applications (pages 4869–4875)

      Yeon-Ji Oh, Goeun Choi, Prof. Young Bin Choy, Dr. Je Won Park, Jung Hyun Park, Prof. Hwa Jeong Lee, Prof. Yeo Joon Yoon, Hee Chul Chang and Prof. Jin-Ho Choy

      Version of Record online: 21 FEB 2013 | DOI: 10.1002/chem.201203384

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      Please release me: From an in vitro release study, the drug-release fraction for the AEA-coated aripiprazole[BOND]montmorillonite (APZ-MMT) hybrid material was determined to be enhanced up to about 95 % in simulated gastric solution (see figure; AEA=polyvinylacetal diethylamino acetate).

    18. Domino Reactions

      Enantioselective Total Synthesis of (−)-Diversonol (pages 4876–4882)

      Prof. Dr. Lutz F. Tietze, Stefan Jackenkroll, Dr. Christian Raith, Dr. Dirk A. Spiegl, Johannes R. Reiner and Maria Claudia Ochoa Campos

      Version of Record online: 18 FEB 2013 | DOI: 10.1002/chem.201204037

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      Domino at its best: An enantioselective domino-Wacker/carbonylation/methoxylation reaction was performed in the total synthesis of the fungal metabolite diversonol (see scheme). Furthermore, synthesis of diastereomeric rac-1,9a-epi-diversonol is also described.

    19. Organic–Inorganic Hybrid Materials

      Design of In Vitro Bioactive Hybrid Materials from the First Generation of Amine Dendrimers as Nanobuilding Blocks (pages 4883–4895)

      Dr. Blanca González, Dr. Montserrat Colilla and Prof. Dr. María Vallet-Regí

      Version of Record online: 21 FEB 2013 | DOI: 10.1002/chem.201203812

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      Family affair: A family of bioactive organic–inorganic hybrid materials of class II has been developed as monolithic pieces by using sol–gel chemistry, starting from the first generation of poly(propyleneimine) dendrimers as nanobuilding blocks and Ca and P sources (see figure; SBF=simulated body fluid). Only hybrid materials that were synthesized through an acid-catalyzed route showed in vitro bioactivity, with an apatite-like layer on their surfaces after seven days of assay.

    20. Asymmetric Catalysis

      Practical Enantioselective Arylation and Heteroarylation of Aldehydes with In Situ Prepared Organotitanium Reagents Catalyzed by 3-Aryl-H8-BINOL-Derived Titanium Complexes (pages 4896–4905)

      Ami Uenishi, Yuya Nakagawa, Hironobu Osumi and Prof. Dr. Toshiro Harada

      Version of Record online: 21 FEB 2013 | DOI: 10.1002/chem.201203946

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      Titanium does it! Titanium complexes derived from 3-aryl-H8-BINOLs exhibit excellent catalytic activity in terms of enantioselectivity and turnover efficiency, providing diaryl-, aryl heteroaryl-, and diheteroarylmethanol derivatives in high enantioselectivity at low catalyst loading (0.2–2 mol %; see scheme).

    21. Organometallic Catalysis

      Group IV Organometallic Compounds Based on Dianionic “Pincer” Ligands: Synthesis, Characterization, and Catalytic Activity in Intramolecular Hydroamination Reactions (pages 4906–4921)

      Dr. Lapo Luconi, Dr. Andrea Rossin, Dr. Alessandro Motta, Dr. Giulia Tuci and Dr. Giuliano Giambastiani

      Version of Record online: 18 FEB 2013 | DOI: 10.1002/chem.201203644

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      Changing the order of the “factors” can (somehow) change the result! Neutral ZrIV and HfIV diamido complexes stabilized by unsymmetrical dianionic N,C,N′-pincer ligands have been prepared (see picture) and successfully employed as good catalyst candidates for the efficient and mild intramolecular hydroamination/cyclization of primary aminoalkenes.

    22. Supramolecular Chemistry

      pH-Controlled Reversible Formation of a Supramolecular Hyperbranched Polymer Showing Fluorescence Switching (pages 4922–4930)

      Bingran Yu, Dr. Baoyan Wang, Shuwen Guo, Qian Zhang, Xiaorui Zheng, Haitao Lei, Prof. Dr. Weisheng Liu, Prof. Dr. Weifeng Bu, Yun Zhang and Dr. Xin Chen

      Version of Record online: 18 FEB 2013 | DOI: 10.1002/chem.201204315

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      Branching out: A supramolecular hyperbranched polymer, TFA-1, has been reversibly fabricated by successively adding acid and base to a conjugated AB2 monomer (1) in CH2Cl2 (see scheme). The driving force behind its assembly is based on acid–base-controllable host–guest recognition between the dibenzo[24]crown-8 moiety and dialkylammonium ion centres. This reversible process is associated with the establishment of π–π stacking interactions between the conjugated cores in solution, which affects the observed fluorescence intensity.

  7. Correspondence

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Correspondence
    1. Cyclic Hydrocarbons

      A Computational Evaluation of the Evidence for the Synthesis of 1,3-Dimethylcyclobutadiene in the Solid State and Aqueous Solution (pages 4932–4937)

      Prof. Henry S. Rzepa

      Version of Record online: 15 MAR 2013 | DOI: 10.1002/chem.201102942

      Density functional calculations of 1H NMR spectra and reaction barriers at the ωB97XD/6-311G(d,p)/continuum water level do not support the claimed identification of encarcerated 1,3-dimethylcyclobutadiene in either the solid state or aqueous solution. Instead, previous suggestions that the species identified in the solid state is in fact 2-oxabicyclo[2.2.0]hex-5-en-3-one are reaffirmed.

    2. Reply to A Computational Evaluation of the Evidence for the Synthesis of 1,3-Dimethylcyclobutadiene in Solid State and Aqueous Solution—Beyond the Experimental Reality (pages 4938–4941)

      Dr. Yves-Marie Legrand, Dan Dumitrescu, Dr. Arnaud Gilles, Eddy Petit, Dr. Arie van der Lee and Dr. Mihail Barboiu

      Version of Record online: 15 MAR 2013 | DOI: 10.1002/chem.201203235

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      Compare what is comparable: When applying theoretical procedures to model complex systems it is important to make sure that one can really compare the systems involved and that the systems applied do not give a rather over-simplified view that becomes too far removed from experimental reality. The models applied in the case of 1,3-dimethylcyclobutadiene by Rzepa are too mobile to preserve the confined stabilizing space defined by the crystalline matrix for encapsulated hosts and too rigid and static compared to the complex dynamic equilibria occurring in solution, which are dependent on experimental conditions (temperature, concentration, ionic strength) to accurately model the NMR spectra of exchanging species in solution.

    3. Reinvestigation of “Single-Crystal X-ray Structure of 1,3-dimethylcyclobutadiene” (pages 4942–4945)

      Prof. Michael Shatruk and Prof. Igor V. Alabugin

      Version of Record online: 15 MAR 2013 | DOI: 10.1002/chem.201103017

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      An alternative explanation: The recent manuscript by Barboiu et al. claims trapping of photochemically generated 1,3-dimethylcyclobutadiene within a hemicarcerand host and determination of its crystal structure. Herein an alternative structural model is offered that demonstrates one does not need to invoke unconventional and highly unstable species to satisfactorily explain the observed electron density in the host cavity.

    4. A Constrained Disorder Refinement: “Reinvestigation of “Single-Crystal X-ray Structure of 1,3-Dimethylcyclobutadiene” by M. Shatruk and I. V. Alabugin” (pages 4946–4950)

      Dr. Yves-Marie Legrand, Dan Dumitrescu, Dr. Arnaud Gilles, Eddy Petit, Dr. Arie van der Lee and Dr. Mihail Barboiu

      Version of Record online: 15 MAR 2013 | DOI: 10.1002/chem.201203234

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      A question of refinement: In this response to the Correspondence by Shatruk and Alabugin, in which they propose an alternative structural model for the observed electron density that was attributed by us to the photochemical formation of 1,3-dimethylcyclobutadiene in a protective solid crystalline matrix, it is demonstrated that they have over-modeled our data by assigning a small electron density peak (O1A), which is hardly more than the density corresponding to a hydrogen atom, to an under-occupied oxygen site, using inappropriate refinement constraints.

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