Chemistry - A European Journal

Cover image for Vol. 18 Issue 40

October 1, 2012

Volume 18, Issue 40

Pages 12533–12901

  1. Cover Pictures

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. Corrigendum
    5. News
    6. Review
    7. Communications
    8. Full Papers
    1. You have free access to this content
      Cover Picture: Water Oxidation with Molecularly Defined Iridium Complexes: Insights into Homogeneous versus Heterogeneous Catalysis (Chem. Eur. J. 40/2012) (page 12533)

      Dr. Henrik Junge, Dr. Nicolas Marquet, Anja Kammer, Stefania Denurra, Prof. Dr. Matthias Bauer, Dr. Sebastian Wohlrab, Felix Gärtner, Dr. Marga-Martina Pohl, Dr. Anke Spannenberg, Prof. Dr. Serafino Gladiali and Prof. Dr. Matthias Beller

      Article first published online: 25 SEP 2012 | DOI: 10.1002/chem.201290172

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      Water oxidationis a significant and challenging goal. Successfully applied molecularly defined Ir complexes are thought to be converted into Ir-oxo nanoparticles that may also act as catalysts. Thus, the iridium performs “tightrope-walking” between homogeneous and heterogeneous catalysis. New insights have been revealed by XANES, EXAFS, and STEM investigations. For more details, see the Full Paper by M. Beller et al. on page 12749 ff.

    2. You have free access to this content
      Inside Cover: Aza-BODIPY Derivatives: Enhanced Quantum Yields of Triplet Excited States and the Generation of Singlet Oxygen and their Role as Facile Sustainable Photooxygenation Catalysts (Chem. Eur. J. 40/2012) (page 12534)

      Nagappanpillai Adarsh, Madhesh Shanmugasundaram, Dr. Rekha R. Avirah and Dr. Danaboyina Ramaiah

      Article first published online: 25 SEP 2012 | DOI: 10.1002/chem.201290173

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      Aza-BODIPY systems possess strong red absorption, exhibit high triplet excited states, and singlet-oxygen generation yields. The aza-BODIPY systems synthesized by D. Ramaiah et al. and reported in their Full Paper on page 12655 ff. are stable under irradiation conditions, act as green catalysts for photooxygenation reactions, and are efficient sensitizers for photodynamic therapy.

    3. You have free access to this content
      Back Cover: The Effects of Substituents on the Geometry of π–π Interactions (Chem. Eur. J. 40/2012) (page 12904)

      Dr. Seth E. Snyder, Bin-Syuan Huang, Yu W. Chu, Huei-Shian Lin and Prof. Dr. James R. Carey

      Article first published online: 25 SEP 2012 | DOI: 10.1002/chem.201290176

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      A series of benzoyl leucine amides of varying electronic character were prepared. All of the 3- and 3,5-disubstituted compounds assembled into homochiral dimers in the solid state. However, no homochiral dimerization was observed in the unsubstituted case and in several 4-substituted cases (shown in yellow). The crystallographic data suggests that local interactions between the dipoles may stabilize the interaction in several of the dimers (shown in red) and provides a driving force for homochiral dimerization. For more details see the Full Paper by J. R. Carey et al. on page 12663 ff.

  2. Graphical Abstract

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

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. Corrigendum
    5. News
    6. Review
    7. Communications
    8. Full Papers
    1. You have free access to this content
      Corrigendum: Macromolecule-to-Amphiphile Conversion Process of a Polyoxometalate–Polymer Hybrid and Assembled Hybrid Vesicles (page 12547)

      Yu Xiao, Dr. Yao-Kun Han, Dr. Nan Xia, Min-Biao Hu, Ping Zheng and Prof. Wei Wang

      Article first published online: 25 SEP 2012 | DOI: 10.1002/chem.201203263

      This article corrects:

      Macromolecule-to-Amphiphile Conversion Process of a Polyoxometalate–Polymer Hybrid and Assembled Hybrid Vesicles

      Vol. 18, Issue 36, 11325–11333, Article first published online: 24 JUL 2012

  4. News

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

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

      Iminium Ions as Dienophiles in Aza-Diels–Alder Reactions: A Closer Look (pages 12554–12582)

      Dr. Misal Giuseppe Memeo and Prof. Paolo Quadrelli

      Article first published online: 11 SEP 2012 | DOI: 10.1002/chem.201201894

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      I′m in ()ium: A review of the origins, modern developments, mechanistic studies and synthetic applications of the iminium variant of the aza-Diels–Alder (iADA) reaction is presented, and the inter- and intramolecular versions of the iADA reactions that are conducted in aqueous solutions to generate the reactive dienophile in situ are discussed (see scheme).

  6. Communications

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

      Anatase TiO2 Mesocrystals Enclosed by (001) and (101) Facets: Synergistic Effects between Ti3+ and Facets for Their Photocatalytic Performance (pages 12584–12589)

      Dr. Qifeng Chen, Prof. Wanhong Ma, Dr. Chuncheng Chen, Dr. Hongwei Ji and Prof. Jincai Zhao

      Article first published online: 21 AUG 2012 | DOI: 10.1002/chem.201201178

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      Let′s facet it: TiO2 mesocrystals (MCs; see figure) enclosed by (101) and (001) facets can be synthesized by a facile green approach and the ratio of (101)/(001) can be tuned simply by adjusting the solvothermal periods. The photocatalytic activity of TiO2 MCs exposing high proportions of (101) facets possess higher photocatalytic activity than those with lower facets; this can be attributed to the synergistic effect of Ti3+ and the (101)/(001) facet ratio.

    2. Arylation

      Palladium-Catalyzed Dehydrogenative β′-Arylation of β-Keto Esters under Aerobic Conditions: Interplay of Metal and Brønsted Acids (pages 12590–12594)

      Kai-Tai Yip, Roshan Y. Nimje, Mikko V. Leskinen and Petri M. Pihko

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201201988

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      The Brønsted aids: The first dehydrogenative arylation of β-keto esters with arenes under ambient aerobic conditions is described (see scheme). Under a PdII/Brønsted acid co-catalytic system, regioselective arylations with alkoxylated arenes and phenols were achieved in good yields, even in gram-scale conditions.

    3. Carbonylation

      Palladium-Catalyzed Carbonylation Reaction of Aryl Bromides with 2-Hydroxyacetophenones to Form Flavones (pages 12595–12598)

      Dr. Xiao-Feng Wu, Dr. Helfried Neumann and Prof. Dr. Matthias Beller

      Article first published online: 24 AUG 2012 | DOI: 10.1002/chem.201202141

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      Flavone of the month: A general and efficient method for the palladium-catalyzed carbonylative synthesis of flavones has been developed (see scheme). Starting from aryl bromides and 2-hydroxyacetophenones, the corresponding flavones have been isolated in good yields.

    4. A General Palladium-Catalyzed Carbonylative Synthesis of 2-Alkylbenzoxazinones from 2-Bromoanilines and Acid Anhydrides (pages 12599–12602)

      Dr. Xiao-Feng Wu, Dr. Helfried Neumann and Prof. Dr. Matthias Beller

      Article first published online: 3 SEP 2012 | DOI: 10.1002/chem.201202142

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      (C), its (O)K! An efficient palladium-catalyzed carbonylative synthesis of 2-alkylbenzoxazinones has been developed (see scheme). By starting from 2-bromoanilines and acid anhydrides, the corresponding products were isolated in good yields.

    5. Metallanucleobases

      The Selective Synthesis of Metallanucleosides and Metallanucleotides: A New Tool for the Functionalization of Nucleic Acids (pages 12603–12608)

      Mamen Martín-Ortíz, Prof. Dr. Mar Gómez-Gallego, Prof. Dr. Carmen Ramírez de Arellano and Prof. Dr. Miguel A. Sierra

      Article first published online: 30 AUG 2012 | DOI: 10.1002/chem.201202327

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      Nucleobases team up: The efficient and selective preparation of purine-derived metallanucleosides, metallanucleotides, and metalladinucleotides having M[BOND]C bonds (M=IrIII, RhIII) is reported for the first time (see scheme). The results presented may be applied to the synthesis of functionalized nucleic acids, or DNA/RNA-modified segments.

    6. DNA Damage

      Hypoxia-Selective DNA Interstrand Cross-Link Formation by Two Modified Nucleosides (pages 12609–12613)

      Dr. Yunyan Kuang, Dr. Huabing Sun, Dr. J. Craig Blain and Prof. Xiaohua Peng

      Article first published online: 31 AUG 2012 | DOI: 10.1002/chem.201201960

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      The clean crossed code: Two nitroimidazole-modified thymidines 1 a and 1 b were synthesized and incorporated into DNA oligomers. The 350 nm photolysis of 1 a and 1 b generated a 5-(2′-deoxyuridinyl)methyl radical that induced DNA interstrand cross-links (ICL; see scheme). A higher ICL yield was observed under hypoxic conditions than under aerobic conditions.

    7. Domino Reactions

      Catalytic Asymmetric Construction of Spiro(γ-butyrolactam-γ-butyrolactone) Moieties through Sequential Reactions of Cyclic Imino Esters with Morita–Baylis–Hillman Bromides (pages 12614–12618)

      Huai-Long Teng, He Huang and Prof. Dr. Chun-Jiang Wang

      Article first published online: 27 AUG 2012 | DOI: 10.1002/chem.201201475

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      Spiro(γ-butyrolactam-γ-butyrolactone): A route to enantioenriched spiro(γ-butyrolactam-γ-butyrolactone) compounds, a valuable motif for drug discovery, was developed by use of a highly efficient copper(I)/TF-BiphamPhos-catalyzed tandem Michael addition–elimination of homoserine lactone derived cyclic imino esters with Morita–Baylis–Hillman (MBH) bromides, followed by treatment with para-toluenesulfonic acid (see scheme).

    8. Porphyrins

      Changes of the Molecule–Substrate Interaction upon Metal Inclusion into a Porphyrin (pages 12619–12623)

      Dr. Giovanni Di Santo, Dr. Cristina Sfiligoj, Dr. Carla Castellarin-Cudia, Dr. Alberto Verdini, Dr. Albano Cossaro, Prof. Alberto Morgante, Dr. Luca Floreano and Dr. Andrea Goldoni

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201201640

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      Metal-dependent conformations: A change in the adaptation of tetraphenylporphyrins (TPPs) on Ag(111) was observed in the presence of a metal ion in the macrocycle. Upon annealing at T>575 K, 2H-TPP molecules increase the overlap of the phenyl π orbitals with the substrate, thus reducing the distance. The presence of Co creates a strong bond between Co dmath image and the Ag sp states, leaving the porphyrin macrocycle at a larger distance to the surface (see figure).

    9. Multicomponent Reactions

      Organocatalytic Enantioselective One-Pot Four-Component Ugi-Type Multicomponent Reaction for the Synthesis of Epoxy-tetrahydropyrrolo[3,4-b]pyridin-5-ones (pages 12624–12627)

      Dr. Yingpeng Su, Dr. Marinus J. Bouma, Dr. Lilian Alcaraz, Dr. Mike Stocks, Dr. Mark Furber, Dr. Géraldine Masson and Prof. Dr. Jieping Zhu

      Article first published online: 28 AUG 2012 | DOI: 10.1002/chem.201202174

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      Enantioselective multicomponent reaction: In the presence of a catalytic amount of chiral BINOL-derived phosphoric acid (TRIP), the reaction of an α-isocyanoacetate 1, an aldehyde 2, and an aniline 3, followed by addition of a toluene solution of α,β-unsaturated acyl chloride 4 afforded the oxa-bridged tricycle 5 in excellent yield, diastereoselectivity, and enantioselectivity. Six chemical bonds, five stereogenic centers, and three cycles were formed in this one-pot four-component reaction.

    10. Nanoparticles

      Regio- and Chemoselective Reduction of Nitroarenes and Carbonyl Compounds over Recyclable Magnetic Ferrite[BOND]Nickel Nanoparticles (Fe3O4[BOND]Ni) by Using Glycerol as a Hydrogen Source (pages 12628–12632)

      Dr. Manoj B. Gawande, Dr. Anuj K. Rathi, Prof. Dr. Paula S. Branco, Dr. Isabel D. Nogueira, Prof. Dr. Alexandre Velhinho, Dr. Janhavi J. Shrikhande, Dr. Utkarsha U. Indulkar, Prof. Dr. Radha V. Jayaram, Dr. C. Amjad A. Ghumman, Dr. Nenad Bundaleski and Prof. Orlando M. N. D. Teodoro

      Article first published online: 30 AUG 2012 | DOI: 10.1002/chem.201202380

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      Reduction by magnetic nano-Fe3O4–Ni: A facile, simple and environmentally friendly hydrogen-transfer reaction that takes place over recyclable ferrite–nickel magnetic nanoparticles (Fe3O4[BOND]Ni) by using glycerol as hydrogen source allows aromatic amines and alcohols to be synthesized from the precursor nitroarenes and carbonyl compounds (see figure).

    11. Anion–Anion Interactions

      From “Loose” to “Dense” Crystalline Phases of Calcium Carbonate through “Repulsive” Interactions: An Experimental Charge-Density Study (pages 12633–12636)

      Dr. Yulia V. Nelyubina and Prof. Konstantin A. Lyssenko

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201201457

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      Anionanion interactions in an eggshell: Experimental electron density analysis for two polymorphs of calcium carbonate revealed why the less stable form, aragonite, has higher density than the most stable form, calcite. Although believed to be exclusively repulsive, the interactions between anions cause them to bind more tightly in a crystal and thus make the aragonite phase denser than its calcite counterpart (see figure).

    12. Biosensors

      Visual Detection of Glucose Using Conformational Switch of i-Motif DNA and Non-Crosslinking Gold Nanoparticles (pages 12637–12642)

      Wen Li, Lingyan Feng, Prof. Jinsong Ren, Li Wu and Prof. Xiaogang Qu

      Article first published online: 30 AUG 2012 | DOI: 10.1002/chem.201201914

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      i-Motif tuned: Glucose is a ubiquitous fuel for metabolic pathways; its oxidation can trigger i-motif DNA formation. Using this unique conformational switch and non-crosslinking gold nanoparticles, a label-free colorimetric glucose sensor has been developed (see illustration).

  7. Full Papers

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. Corrigendum
    5. News
    6. Review
    7. Communications
    8. Full Papers
    1. Molecular Switching

      Multiple States of Dimeric Aggregates Formed by (Amido–ethynyl)helicene Bidomain Compound and (Amido–ethynyl–amido)helicene Tridomain Compound (pages 12644–12654)

      Dr. Wataru Ichinose, Dr. Masanori Shigeno and Prof. Dr. Masahiko Yamaguchi

      Article first published online: 11 SEP 2012 | DOI: 10.1002/chem.201201929

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      Domain switching! An (amido–ethynyl)helicene bidomain compound and an (amido–ethynyl–amido)helicene tridomain compound were synthesized. Four aggregate states of multidomain compounds, namely, all-dimer, amido-dimer, ethynyl-dimer, and random-coil states, were obtained in different solvents. Each domain independently aggregated and disaggregated in a two-state manner. Two different reversible structural changes occurred between the ethynyl-dimer/random-coil and the all-dimer/amido-dimer with heating and cooling.

    2. Photooxidation

      Aza-BODIPY Derivatives: Enhanced Quantum Yields of Triplet Excited States and the Generation of Singlet Oxygen and their Role as Facile Sustainable Photooxygenation Catalysts (pages 12655–12662)

      Nagappanpillai Adarsh, Madhesh Shanmugasundaram, Dr. Rekha R. Avirah and Dr. Danaboyina Ramaiah

      Article first published online: 3 SEP 2012 | DOI: 10.1002/chem.201202438

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      Aza-BODIPY derivatives were synthesized and their triplet excited states and yields of singlet-oxygen generation were tuned by halogenation. The dye that was substituted with six iodine atoms showed the highest quantum yields of the triplet excited state (ΦT=0.86) and singlet oxygen (ΦΔ=0.80). These systems were stable to irradiation, had strong NIR absorption, exhibited high yields of singlet oxygen, and acted as catalysts for photooxygenation reactions (see figure).

    3. π–π Interactions

      The Effects of Substituents on the Geometry of π–π Interactions (pages 12663–12671)

      Dr. Seth E. Snyder, Bin-Syuan Huang, Yu W. Chu, Huei-Shian Lin and Prof. Dr. James R. Carey

      Article first published online: 10 SEP 2012 | DOI: 10.1002/chem.201202253

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      To dimerize or not to dimerize? The position of a substituent on an aromatic moiety can have a profound effect on π–π interactions. In the present study, involving 4-substituted benzoyl leucine diethyl amides, only certain compounds formed homochiral dimers with a stabilizing parallel displaced π–π interaction (see figure). The crystallographic data suggest that local interactions between dipoles may provide a driving force for self-assembly and for homochiral dimerization.

    4. Metallocenes

      Synthesis and Characterization of Multiferrocenyl-Substituted Group 4 Metallocene Complexes (pages 12672–12680)

      Dr. Katharina Kaleta, Frank Strehler, Dr. Alexander Hildebrandt, Dr. Torsten Beweries, Dr. Perdita Arndt, Dr. Tobias Rüffer, Dr. Anke Spannenberg, Prof. Dr. Heinrich Lang and Prof. Dr. Uwe Rosenthal

      Article first published online: 3 SEP 2012 | DOI: 10.1002/chem.201202188

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      Super-crowded metallocenes: The reaction of diferrocenylacetylene and 1,4-diferrocenylbuta-1,3-diyne with Group 4 metallocene compounds yields attractive multiferrocenyl complexes. Depending on the metal, different products were obtained by complexation, coupling, or C[BOND]C bond cleavage of the ligand (see scheme). Their electrochemical properties were studied in detail. The oxidation of the metallacycle induces decomposition of the complexes.

    5. Vancomycin

      Elucidation of the Active Conformation of Vancomycin Dimers with Antibacterial Activity against Vancomycin-Resistant Bacteria (pages 12681–12689)

      Dr. Jun Nakamura, Hidenori Yamashiro, Sayaka Hayashi, Mami Yamamoto, Kenji Miura, Dr. Shu Xu, Prof. Dr. Takayuki Doi, Dr. Hideki Maki, Osamu Yoshida and Prof. Dr. Hirokazu Arimoto

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201201211

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      Squashing superbugs: Conformationally constrained vancomycin dimers that inhibit the peptidoglycan synthesis of vancomycin-resistant bacteria were prepared (see scheme). The potent antibacterial activity of the dimers was suggested to arise from their direct action on transglycosylase enzymes.

    6. Fluorescent Compounds

      Synthesis of a Library of Fluorescent 2-Aryl-3-trifluoromethylnaphthofurans from Naphthols by Using a Sequential Pummerer-Annulation/Cross-Coupling Strategy and their Photophysical Properties (pages 12690–12697)

      Yuuya Ookubo, Prof. Dr. Atsushi Wakamiya, Prof. Dr. Hideki Yorimitsu and Prof. Dr. Atsuhiro Osuka

      Article first published online: 28 AUG 2012 | DOI: 10.1002/chem.201201261

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      Generation next: Pummerer annulation of simple naphthols followed by cross-coupling with various arylzinc reagents allows the concise and diversity-oriented synthesis of a library of fluorescent naphthofurans (see scheme).

    7. Combinatorial Chemistry

      Expanding the Scope of PNA-Encoded Synthesis (PES): Mtt-Protected PNA Fully Orthogonal to Fmoc Chemistry and a Broad Array of Robust Diversity-Generating Reactions (pages 12698–12704)

      Dalila Chouikhi, Mihai Ciobanu, Claudio Zambaldo, Vincent Duplan, Dr. Sofia Barluenga and Prof. Nicolas Winssinger

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201201337

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      Keeping track of a library: A strategy that is compatible with a large palette of reactions that have been productively used in diversity-oriented synthesis (palladium cross-couplings, metathesis, π-allylation, CuAAC, reductive amination, amidation, heterocycle formation, nucleophilic addition, conjugate additions, Pictet– Spengler cyclization) is described (see figure).

    8. Polymerization

      Polymeric Adsorption of Methylene Blue in TiO2 Colloids—Highly Sensitive Thermochromism and Selective Photocatalysis (pages 12705–12711)

      Dr. Baoshun Liu, Liping Wen, Dr. Kazuya Nakata, Prof. Dr. Xiujian Zhao, Shanhu Liu, Dr. Tsuyoshi Ochiai, Dr. Taketoshi Murakami and Prof. Dr. Akira Fujishima

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201200178

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      Three is the magic number! Methylene blue (MB) favors adsorption on TiO2 colloid surfaces in the trimeric low-energy state (see figure) because of strong electrostatic attractions. The trimer–monomer equilibrium of MB on TiO2 surfaces is highly sensitive to temperature changes, resulting in a reversible thermochromism. Due to highly selective adsorption, the TiO2 colloid also shows very selective photocatalysis of MB and other cationic dyes.

    9. Sensors

      Iptycene-Based Fluorescent Sensors for Nitroaromatics and TNT (pages 12712–12718)

      Dr. Pavel Anzenbacher Jr., Dr. Lorenzo Mosca, Dr. Manuel A. Palacios, Dr. Grigory V. Zyryanov and Petr Koutnik

      Article first published online: 28 AUG 2012 | DOI: 10.1002/chem.201200469

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      TNT is sensed! Fluorescent sensors based on the iptycene recognition motif were synthesised and studied with different nitroaromatic compounds. X-ray structures confirm the establishment of edge-to-face interactions. Fluorescence studies in solution and in polymer matrices allowed the development of polymer-nanofibre sensors for the detection of nitroaromatic compounds and TNT (see figure).

    10. Drug Detection

      Competitive Assay for Theophylline Based on an Abasic Site-Containing DNA Duplex Aptamer and a Fluorescent Ligand (pages 12719–12724)

      Dr. Yusuke Sato, Yushuang Zhang, Dr. Seiichi Nishizawa, Dr. Takehiro Seino, Kodai Nakamura, Dr. Minjie Li and Prof. Dr. Norio Teramae

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201201298

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      Lighting up the competition: A fluorescence assay is reported for the detection of theophylline by using an abasic site (AP site)-containing DNA duplex aptamer (AP aptamer) in combination with an abasic site-binding fluorescent ligand, namely riboflavin. The assay is based on the competitive binding of theophylline or riboflavin at the AP site of the AP aptamer (see scheme). Fluorescence detection of theophylline was successfully demonstrated with high selectivity in serum samples by using the optimized AP aptamer and riboflavin.

    11. Tautomerization

      Solvent-Catalyzed Ring–Chain–Ring Tautomerization in Axially Chiral Compounds (pages 12725–12732)

      Asli Yildirim, Prof. Dr. Fethiye Aylin Sungur Konuklar, Dr. Saron Catak, Prof. Dr. Veronique Van Speybroeck, Prof. Dr. Michel Waroquier, Prof. Dr. Ilknur Dogan and Prof. Dr. Viktorya Aviyente

      Article first published online: 13 SEP 2012 | DOI: 10.1002/chem.201200363

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      Tautomerism mechanisms: 2-Oxazolidinone derivatives have the potential to be used as axially chiral catalysts. However, they thermally interconvert by a ring–chain–ring tautomerization mechanism (see scheme). DFT calculations provide a thorough understanding of this mechanism as well as the effect of solvent assistance, which is crucial for facilitating proton transfer.

    12. Bonding Analysis

      Transition-Metal Complexes of Tetrylones [(CO)5W-E(PPh3)2] and Tetrylenes [(CO)5W-NHE] (E=C–Pb): A Theoretical Study (pages 12733–12748)

      Thi Ai Nhung Nguyen and Prof. Dr. Gernot Frenking

      Article first published online: 3 SEP 2012 | DOI: 10.1002/chem.201200741

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      Opposite bonding trends: Quantum chemical calculations suggest that the bond strength of W[BOND]E (E=C–Pb) in the experimentally yet unknown tetrylone complexes W-1 E increases for the heavier Group 14 elements from carbon to lead, whereas the W[BOND]E bond in the tetrylene complexes W-2 E becomes weaker for the heavier atoms. The heavier ligands prefer a side-on bonding mode in both series of compounds.

    13. Iridium

      Water Oxidation with Molecularly Defined Iridium Complexes: Insights into Homogeneous versus Heterogeneous Catalysis (pages 12749–12758)

      Dr. Henrik Junge, Dr. Nicolas Marquet, Anja Kammer, Stefania Denurra, Prof. Dr. Matthias Bauer, Dr. Sebastian Wohlrab, Felix Gärtner, Dr. Marga-Martina Pohl, Dr. Anke Spannenberg, Prof. Dr. Serafino Gladiali and Prof. Dr. Matthias Beller

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201201472

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      Ir walks a fine line: Molecularly defined Ir complexes and IrO2 nanoparticles have been applied in the water oxidation reaction with cerium ammonium nitrate (CAN) as oxidant and compared (see scheme). The conversion of the first to the latter has been investigated by means of XANES, EXAFS, and STEM.

    14. Conformation Analysis

      Shapes and Internal Dynamics of the 1:1 Adducts of Ammonia with trans and gauche Ethanol: A Rotational Study (pages 12759–12763)

      Dr. Barbara M. Giuliano, Dr. Laura B. Favero, Dr. Assimo Maris and Prof. Dr. Walther Caminati

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201201664

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      A complex situation: Two different conformers of the ethanol[BOND]NH3 complex have been characterized by Fourier transform microwave spectroscopy. NH3 is linked to the gauche or trans forms of ethanol through an O[BOND]H⋅⋅⋅N hydrogen bond. The effects of three large amplitude motions (internal rotation of the CH3 group, almost-free rotation of the NH3 moiety, and tunneling between the two equivalent gauche forms) were observed.

    15. Near-Infrared Emission

      Efficient NIR-Light Emission from Solid-State Complexes of Boron Difluoride with 2′-Hydroxychalcone Derivatives (pages 12764–12772)

      Dr. Anthony D'Aléo, Dr. David Gachet, Dr. Vasile Heresanu, Dr. Michel Giorgi and Prof. Frédéric Fages

      Article first published online: 30 AUG 2012 | DOI: 10.1002/chem.201201812

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      Tint it black! Complexation with boron difluoride converts 2′-hydroxychalcone derivatives into strongly absorbing/emitting dyes. These darkly colored crystalline solids exhibit NIR emission, owing to densely packed π-stacks of dipolar chromophores.

    16. Schiff Bases

      Schiff Base Structured Acid–Base Cooperative Dual Sites in an Ionic Solid Catalyst Lead to Efficient Heterogeneous Knoevenagel Condensations (pages 12773–12782)

      Mingjue Zhang, Pingping Zhao, Dr. Yan Leng, Guojian Chen, Prof. Dr. Jun Wang and Prof. Dr. Jun Huang

      Article first published online: 21 AUG 2012 | DOI: 10.1002/chem.201201338

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      Cooperative catalyst: The ionic solid prepared by pairing pyridine-based Schiff base tethered cations with phosphotungstate anions is proved to be a recoverable efficient heterogeneous catalyst for Knoevenagel condensations by means of the unique bulk-type acid–base cooperative mechanism (see scheme).

    17. Glycopeptides

      Influence of Sequential Modifications and Carbohydrate Variations in Synthetic AFGP Analogues on Conformation and Antifreeze Activity (pages 12783–12793)

      Dr. Lilly Nagel, Dr. Carsten Budke, Roman S. Erdmann, Dr. Axel Dreyer, Prof. Dr. Helma Wennemers, Prof. Dr. Thomas Koop and Prof. Dr. Norbert Sewald

      Article first published online: 28 AUG 2012 | DOI: 10.1002/chem.201202119

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      Out of the cold: The antifreeze activity of AFGP (antifreeze glycoprotein, see figure) analogues strongly depends on the amino acid composition. Synthetic, near-native compounds (e.g., with proline replacing alanine) retain the effect, whereas others exhibit reduced or abolished influence on ice recrystallization, despite having high propensity to adopt polyproline II helical conformation, as proposed for the native AFGP.

    18. Boron-Containing Compounds

      Disclosing the Structure/Activity Correlation in Trivalent Boron-Containing Compounds: A Tendency Map (pages 12794–12802)

      Jessica Cid, Dr. Jorge J. Carbó and Dr. Elena Fernández

      Article first published online: 30 AUG 2012 | DOI: 10.1002/chem.201200987

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      All mapped out: The properties of boryl fragments that were bonded to main-group metals or coordinated to transition/rare-earth metals were used to create a map that can assist the preparation of trivalent boron species with desired nucleophilicity.

    19. Metallasilatrane Complexes

      Atomic Contributions from Spin-Orbit Coupling to 29Si NMR Chemical Shifts in Metallasilatrane Complexes (pages 12803–12813)

      Prof. Jochen Autschbach, Kiplangat Sutter, Dr. Lionel A. Truflandier, Dr. Erica Brendler and Dr. Jörg Wagler

      Article first published online: 28 AUG 2012 | DOI: 10.1002/chem.201200746

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      All in a spin! The class of metallasilatrane complexes [X-Si-(μ-mt)4-M-Y] with M=Ni, Pd, and Pt, previously reported for X=Y=Cl (shown here), has been extended by new members with X=F and Y=Br and I. New synthetic routes, structural characterizations by X-ray diffraction, and 29Si solid-state NMR data are reported. Spin-orbit effects on the 29Si chemical shifts were investigated with the help of relativistic density functional calculations.

    20. Annulenes

      Molecular Propellers that Consist of Dehydrobenzo[14]annulene Blades (pages 12814–12824)

      Shunpei Nobusue, Yuichi Mukai, Yo Fukumoto, Dr. Rui Umeda, Dr. Kazukuni Tahara, Dr. Motohiro Sonoda and Prof. Yoshito Tobe

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201201061

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      The propellerheads: The behavior of propeller-shaped compounds with dehydrobenzo[14]annulene rings was investigated. Interconversion between the stereoisomers had relatively small energy barriers owing to the flexibility of the acetylene linkages.

    21. Natural Products

      Combining the Power of TiIII-Mediated Processes for Easy Access to Hydroxylated Polycyclic Terpenoids: Synthesis of Sesterstatin 1 and C–D Rings of Aspergilloxide (pages 12825–12833)

      Tania Jiménez, Sara P. Morcillo, Ana Martín-Lasanta, Daniel Collado-Sanz, Prof. Dr. Diego J. Cárdenas, Prof. Dr. Andreas Gansäuer, Prof. Dr. José Justicia and Prof. Dr. Juan M. Cuerva

      Article first published online: 24 AUG 2012 | DOI: 10.1002/chem.201201534

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      Doing it the easy way: Polyhydroxylated terpenoids are accessed through two titanocene(III)-mediated reactions: a “head-to-tail” Barbier-type addition of prenyl chlorides to α,β-unsaturated aldehydes, which allows the introduction of hydroxy groups at desirable positions of the acyclic precursor, and a subsequent radical cyclisation. This methodology is used in the first total synthesis of sesterstatin 1 and a model compound of the C–D rings of aspergilloxide (see scheme).

    22. Radical Polymerization

      Key Role of Intramolecular Metal Chelation and Hydrogen Bonding in the Cobalt-Mediated Radical Polymerization of N-Vinyl Amides (pages 12834–12844)

      Dr. Antoine Debuigne, Aurélie N. Morin, Dr. Anthony Kermagoret, Dr. Yasmine Piette, Dr. Christophe Detrembleur, Prof. Christine Jérôme and Prof. Rinaldo Poli

      Article first published online: 21 AUG 2012 | DOI: 10.1002/chem.201201456

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      Growing the chain: In addition to reversible cobalt[BOND]carbon bond formation, an intramolecular metal chelation phenomenon occurs in the cobalt-mediated radical polymerization (CMRP) of N-vinyl amides (see scheme). The latter reinforces the metal[BOND]polymer bond and allows optimal control of the polymerizations of N-vinyl caprolactam and N-methyl vinyl acetamide. The detrimental effect of hydrogen bond formation in the CMRP of N-vinyl acetamide and N-vinyl formamide is also considered.

    23. Metathesis

      Fast Olefin Metathesis at Low Catalyst Loading (pages 12845–12853)

      Dr. Lars H. Peeck, Roman D. Savka and Prof. Herbert Plenio

      Article first published online: 28 AUG 2012 | DOI: 10.1002/chem.201201010

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      The tortoise and the hare: The use of diphenylalkylamino-based instead of phenyldialkylamino-based styrenes (see figure) leads to rapidly initiating precatalysts that enable very fast ring-closing metathesis reactions with turnover numbers of up to 58 000 and turnover frequencies of up to 232 000 h−1.

    24. Porphyrins

      Retro-Diels–Alder Approach to the Synthesis of π-Expanded Azuliporphyrins and Their Porphyrinoid Aromaticity (pages 12854–12863)

      Prof. Dr. Tetsuo Okujima, Tasuku Kikkawa, Prof. Dr. Haruyuki Nakano, Hiroshi Kubota, Nobumasa Fukugami, Prof. Dr. Noboru Ono, Prof. Dr. Hiroko Yamada and Prof. Dr. Hidemitsu Uno

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201201399

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      Porphyrins: A series of azulibenzoporphyrins were synthesized based on 3+1 porphyrin synthesis and retro-Diels–Alder reaction of bicyclo[2.2.2]octadiene-fused precursors (see scheme). UV/Vis spectra and NICS calculations revealed that their diprotonated dications exhibited a low porphyrinoid aromaticity from the porphyrinlike π circuit, which was dependent on the position and number of fused benzene rings.

    25. Host–Guest Chemistry

      Assembly of Water-Soluble, Dynamic, Covalent Container Molecules and Their Application in the Room-Temperature Stabilization of Protoadamantene (pages 12864–12872)

      Dr. Zhihua Lin, Junling Sun, Bisera Efremovska and Dr. Ralf Warmuth

      Article first published online: 22 AUG 2012 | DOI: 10.1002/chem.201200602

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      Molecular nanoflask! Room-temperature stabilization of protoadamantene was achieved inside a water-soluble, dynamic, covalent, hemicarcerand nanoflask. The nanoflask spontaneously assembles from a cavitand and propylenediamine in water in the presence of 3-noradamantyldiazirine as a template (see scheme). Photolysis of the imprisoned diazirine yields the Bredt olefin, which survives for days at room temperature.

    26. Oxidative Coupling

      Ruthenium-Catalyzed Oxidative Coupling/Cyclization of Isoquinolones with Alkynes through C[BOND]H/N[BOND]H Activation: Mechanism Study and Synthesis of Dibenzo[a,g]quinolizin-8-one Derivatives (pages 12873–12879)

      Prof. Dr. Bin Li, Huiliang Feng, Nuancheng Wang, Jianfeng Ma, Prof. Dr. Haibin Song, Prof. Shansheng Xu and Prof. Dr. Baiquan Wang

      Article first published online: 28 AUG 2012 | DOI: 10.1002/chem.201201862

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      All in the detail: A detailed study of the mechanism of the RuII-catalyzed oxidative coupling/cyclization of isoquinolones with alkynes is reported (see scheme). All of the key stages were identified and intermediates were determined by X-ray crystallography. An efficient and highly regioselective [{RuCl2(p-cymene)}2]-catalyzed oxidative annulation of isoquinolones with alkynes to synthesize dibenzo[a,g]quinolizin-8-one derivatives with a broad substrate scope was also developed.

    27. Organic Semiconductors

      2,2′:3′,2′′-Terthiophene-Based all-Thiophene Dendrons and Dendrimers: Synthesis, Structural Characterization, and Properties (pages 12880–12901)

      Dr. Chang-Qi Ma, Dr. Elena Mena-Osteritz, Dr. Markus Wunderlin, Dr. Gisela Schulz and Prof. Dr. Peter Bäuerle

      Article first published online: 21 AUG 2012 | DOI: 10.1002/chem.201200231

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      Branching out all over: all-Thiophene dendrimers up to a fourth generation have been successfully synthesized by a divergent/convergent approach that involves halogenation, boronation, and Suzuki coupling reactions. These highly branched dendritic oligothiophenes are soluble in organic solvents and have a monodispersed nature (see scheme).

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