Chemistry - A European Journal

Cover image for Vol. 18 Issue 22

May 29, 2012

Volume 18, Issue 22

Pages 6693–6987

  1. Cover Picture

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      Cover Picture: “Bottom-Up” Embedding of the Jørgensen–Hayashi Catalyst into a Chiral Porous Polymer for Highly Efficient Heterogeneous Asymmetric Organocatalysis (Chem. Eur. J. 22/2012) (page 6693)

      Chang An Wang, Zhi Kun Zhang, Tao Yue, Ya Lei Sun, Lei Wang, Wei David Wang, Dr. Yuan Zhang, Chong Liu and Prof. Dr. Wei Wang

      Article first published online: 23 MAY 2012 | DOI: 10.1002/chem.201290088

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      The so-called “Bird's Nest” (the framework of the Beijing National Stadium as depicted on the cover), bears a resemblance to the rigid porous catalyst constructed for highly efficient heterogeneous asymmetric organocatalysis by W. Wang et al., reported in their Communication on page 6718 ff. The chiral porous polymer containing the Jørgensen–Hayashi catalyst shows excellent activity in the asymmetric Michael addition reaction.

  2. Graphical Abstract

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    1. Graphical Abstract: Chem. Eur. J. 22/2012 (pages 6696–6705)

      Article first published online: 23 MAY 2012 | DOI: 10.1002/chem.201290089

  3. News

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  4. Concept

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    1. Organocatalysis

      Asymmetric Cyclization Reactions of Allenoates with Imines or α,β-Unsaturated Ketones Catalyzed by Organocatalysts Derived from Cinchona Alkaloids (pages 6712–6716)

      Cheng-Kui Pei and Prof. Min Shi

      Article first published online: 24 APR 2012 | DOI: 10.1002/chem.201200209

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      Asymmetric organocatalysis: Lewis base-catalyzed cyclization reactions of allenoates with electron-deficient olefins and imines have been applied in the preparation of biologically active natural products and pharmaceutically interesting substances and have emerged as powerful synthetic tools in the rapid construction of cyclic molecular complexity. In contrast to phosphine-containing Lewis bases, nitrogen-containing Lewis base amines display markedly different reaction profiles; however, this area is not well-developed.

  5. Communications

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    1. Heterogeneous Organocatalysis

      “Bottom-Up” Embedding of the Jørgensen–Hayashi Catalyst into a Chiral Porous Polymer for Highly Efficient Heterogeneous Asymmetric Organocatalysis (pages 6718–6723)

      Chang An Wang, Zhi Kun Zhang, Tao Yue, Ya Lei Sun, Lei Wang, Wei David Wang, Dr. Yuan Zhang, Chong Liu and Prof. Dr. Wei Wang

      Article first published online: 4 MAY 2012 | DOI: 10.1002/chem.201200753

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      The only way is up! “Bottom-up” construction of a robust chiral porous polymer (JH-CPP) embedded with the Jørgensen–Hayashi catalyst (JH) has been successfully achieved for highly efficient heterogeneous organocatalysis. The high BET surface area, wide openings and interconnected nanopores of JH-CPP increase the accessibility of catalytic sites and as such the catalyst shows excellent activity in catalyzing the asymmetric Michael addition reaction (see scheme).

    2. Asymmetric Synthesis

      Iridium-Catalyzed Enantioselective Hydrogenation of Alkenylboronic Esters (pages 6724–6728)

      Adnan Ganić and Prof. Dr. Andreas Pfaltz

      Article first published online: 24 APR 2012 | DOI: 10.1002/chem.201200246

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      Choose the right ligand: An iridium complex derived from a phosphino–imidazoline ligand is a highly efficient catalyst for the asymmetric hydrogenation of terminal vinyl boronic esters (see scheme). On the other hand, trisubstituted alkenyl-boronates can be reduced with high activity and good to excellent enantioselectivity employing a pyridine–phosphinite ligand.

    3. Natural Products

      Total Synthesis of (±)-Kopsihainanine A (pages 6729–6732)

      Peng Jing, Zhen Yang, Changgui Zhao, Huaiji Zheng, Bowen Fang, Dr. Xingang Xie and Prof. Dr. Xuegong She

      Article first published online: 30 APR 2012 | DOI: 10.1002/chem.201200867

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      Going all the way: The first total synthesis of (±)-kopsihainanine A has been achieved in ten steps with a 12 % overall yield from commercially available 1,2,3,4-tetrahydrocarbazol-4-one (see scheme). This synthesis features an intramolecular conjugate addition of the iminium ion formed in situ with the amide and a substrate-controlled diastereoselective α-hydroxylation. Furthermore, ring D is formed by a late-stage transannular SN2 reaction.

    4. Nanoparticles

      Coating Pt0 Nanoparticles with Methyl Groups: The Reaction Between Methyl Radicals and Pt0[BOND]NPs Suspended in Aqueous Solutions (pages 6733–6736)

      Ronen Bar-Ziv, Dr. Israel Zilbermann, Dr. Tomer Zidki, Guy Yardeni, Prof. Dr. Vladimir Shevchenko and Prof. Dr. Dan Meyerstein

      Article first published online: 24 APR 2012 | DOI: 10.1002/chem.201200593

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      Methyl radicals react with Pt0[BOND]NPs suspended in aqueous solutions in fast reactions. The major product is stable methyl coated Pt0[BOND]NPs, (Pt0[BOND]NPs)[BOND](CH3)n. C2H6, C2H4 and some polymerization products are also formed (see scheme).

    5. Cascade Reactions

      An Organocatalytic Cascade Strategy for the Enantioselective Construction of Spirocyclopentane Bioxindoles Containing Three Contiguous Stereocenters and Two Spiro Quaternary Centers (pages 6737–6741)

      Wangsheng Sun, Gongming Zhu, Chongyang Wu, Liang Hong and Prof. Dr. Rui Wang

      Article first published online: 20 APR 2012 | DOI: 10.1002/chem.201200478

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      A rapid and efficient organocatalytic cascade sequence for the direct construction of spirocyclopentane bioxindoles has been carried out by using a chiral squaramide catalyst in the presence of a base. This process constitutes a powerful approach to the preparation of biologically important bispirooxindoles in high enantioselectivities (see scheme).

    6. Asymmetric Hydrogenation

      Carbon Monoxide Assisted Self-Assembled Platinum Nanoparticles for Catalytic Asymmetric Hydrogenation (pages 6742–6745)

      Dr. Arindam Indra and Prof. Dr. Goutam Kumar Lahiri

      Article first published online: 30 APR 2012 | DOI: 10.1002/chem.201200422

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      Pt NPs CO-operate: Pt nanorods (Pt NRs) have been developed by the self-assembly of uniformly distributed small Pt nanoparticles (Pt NPs, 1.8–2.4 nm), obtained from [Pt(cod)Cl2] (cod=1,5-cyclooctadiene) in the presence of CO in non-aqueous medium. As-synthesized non-supported Pt NRs catalyze the asymmetric hydrogenation of methyl pyruvate and acetophenone to (R)-methyl lactate and (R)-1-phenyl ethanol, respectively (see scheme).

    7. Radiopharmaceuticals

      Emulsion Reactors: A New Technique for the Preparation of Molecular Imaging Probes (pages 6746–6749)

      Dr. Ryan W. Simms, Dr. Dong Hyun Kim, Darren M. Weaver, Dr. Chitra Sundararajan, Megan Blacker, Dr. Karin A. Stephenson and Prof. Dr. John F. Valliant

      Article first published online: 25 APR 2012 | DOI: 10.1002/chem.201200049

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      Emulsions for labeling: A new strategy for the preparation of radiolabeled compounds with the use of emulsions was developed. This biocompatible platform demonstrated enhanced yields for labeling biovectors with 99mTc, 18F, and 68Ga. Enhancements included reduction in the amount of starting material required, a decrease in the number of radiochemical impurities, and the ability to perform reactions at room temperature.

    8. Asymmetric Catalysis

      Manganese Catalysts with C1-Symmetric N4 Ligand for Enantioselective Epoxidation of Olefins (pages 6750–6753)

      Bin Wang, Dr. Chengxia Miao, Shoufeng Wang, Prof. Dr. Chungu Xia and Prof. Dr. Wei Sun

      Article first published online: 24 APR 2012 | DOI: 10.1002/chem.201103802

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      Bioinspired manganese complexes based on N4 ligands, with a more rigid, chiral diamine derived from proline and two benzimidazoles, were synthesized and applied to epoxidize olefins with hydrogen peroxide as a clean oxidant. Notably, 60–99 % isolated yields and excellent ee values (up to 95 %) were obtained by using low catalyst loadings (0.01–0.2 mol %; see scheme; F green, S yellow).

    9. Polyoxometalates

      Supramolecular Assembly of Conjugated Polymers Containing Polyoxometalate Terminal Side Chains in Polar and Nonpolar Solvents (pages 6754–6758)

      Panchao Yin, Lu Jin, Dong Li, Peng Cheng, Prof. Dr. Dmitri V. Vezenov, Emily Bitterlich, Xia Wu, Prof. Dr. Zhonghua Peng and Prof. Dr. Tianbo Liu

      Article first published online: 23 APR 2012 | DOI: 10.1002/chem.201103782

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      Clever combination: Three linear polymers containing polyoxometalate clusters on the side chains have been studied in both polar and nonpolar solvents. These polymers show amphiphilic properties in a nonpolar solvent (toluene) and form reverse vesicular supramolecular aggregates, while displaying polyelectrolyte properties in polar solvents and assembling into hollow tubelike structures (see scheme).

    10. Organodiphosphonate-Functionalized Lanthanopolyoxomolybdate Cages (pages 6759–6762)

      Prof. Jingyang Niu, Xiaoqing Zhang, Donghui Yang, Dr. Junwei Zhao, Pengtao Ma, Prof. Dr. Ulrich Kortz and Prof. Jingping Wang

      Article first published online: 20 APR 2012 | DOI: 10.1002/chem.201200974

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      Building functional cages: The first lanthanide-containing organodiphosphonate-functionalized polyoxomolybdate cages have been prepared. They exhibit interesting photocatalytic properties in the decomposition of organic dyes (see figure).

  6. Full Papers

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    1. Charge Transfer

      Localization/Delocalization of Charges in Bay-Linked Perylene Bisimides (pages 6764–6775)

      Dr. Wei Jiang, Chengyi Xiao, Linxiao Hao, Prof. Zhaohui Wang, Harald Ceymann, Prof. Christoph Lambert, Dr. Simone Di Motta and Prof. Fabrizia Negri

      Article first published online: 3 MAY 2012 | DOI: 10.1002/chem.201103954

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      Charge of the linked brigade: The degree of interaction in the neutral and the reduced forms of bay-linked perylene bisimides (PBIs; see figure) that differ in their linkage is due to the different degrees of twisting and flexibility between the PBI moieties.

    2. Epoxidation

      Catalytic Epoxidations with Peroxides: Molybdenum Trioxide Species as the Origin of Allylic Byproducts (pages 6776–6780)

      Dr. Ulrich Neuenschwander, Emanuel Meier and Prof. Dr. Ive Hermans

      Article first published online: 18 APR 2012 | DOI: 10.1002/chem.201200470

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      Epoxides versus radical byproducts: Catalytic activation of hydroperoxides by MoVI proceeds via metal–peroxide species, which can either epoxidize olefins or form metal–trioxide species upon reaction with hydroperoxide. Homolytic cleavage of the trioxide (see figure) leads to the formation of radicals and therefore limits the epoxide selectivity.

    3. Birefringence

      From Low to Very High Birefringence in Bis(2-pyridylimino)isoindolines: Synthesis and Structure–Property Analysis (pages 6781–6787)

      Edwin W. Y. Wong, Jeffrey S. Ovens and Daniel B. Leznoff

      Article first published online: 18 APR 2012 | DOI: 10.1002/chem.201103421

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      Lobsterates! Three bis(2-pyridylimino)isoindoline (lobsterate) derivatives were synthesized and structurally characterized. The birefringence (Δn) values of these (including the parent lobsterate) were measured, yielding Δn values of 0.06–0.7. These are correlated with the orientation and 3D packing of the molecules in their crystal structure, providing a framework for interpreting birefringence data of known organic molecules.

    4. Immobilization

      Directed Supramolecular Surface Assembly of SNAP-tag Fusion Proteins (pages 6788–6794)

      Dr. Dana A. Uhlenheuer, Dr. Dorothee Wasserberg, Dr. Christian Haase, Dr. Hoang D. Nguyen, Jan Hendrik Schenkel, Prof. Dr. Jurriaan Huskens, Prof. Dr. Bart Jan Ravoo, Dr. Pascal Jonkheijm and Prof. Dr. Luc Brunsveld

      Article first published online: 18 APR 2012 | DOI: 10.1002/chem.201200238

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      SNAP-on tools: Proteins were assembled in a supramolecular and directed manner on cyclodextrin-modified surfaces. The supramolecular host element bisadamantane was incorporated in the proteins in a rapid, facile and site-selective manner by SNAP-tag labeling. The novel supramolecular proteins can be reversibly assembled and disassembled out of solution on micropatterned surfaces and on cyclodextrin vesicles (see figure).

    5. Ionic Liquids

      Ionic Liquids of Cationic Sandwich Complexes (pages 6795–6804)

      Takashi Inagaki, Prof. Dr. Tomoyuki Mochida, Prof. Dr. Masashi Takahashi, Dr. Chikahide Kanadani, Prof. Dr. Toshiaki Saito and Prof. Dr. Daisuke Kuwahara

      Article first published online: 19 APR 2012 | DOI: 10.1002/chem.201200151

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      The earl of sandwich: A series of metal-containing ionic liquids (ILs) that were based on simple cationic sandwich complexes were developed. Ferrocenium ILs were deep-blue paramagnetic fluids, whereas cobaltocenium ILs and arene–ferrocenium ILs were orange and reddish-orange diamagnetic liquids, respectively (see figure). The thermal properties, stabilities, viscosities, 57Fe Mössbauer spectroscopy, and magnetic susceptibility of these ILs were investigated.

    6. Supramolecular Chirality

      Versatile Switching in Substrate Topicity: Supramolecular Chirality Induction in Di- and Trinuclear Host Complexes (pages 6805–6810)

      Dr. Martha V. Escárcega-Bobadilla, Giovanni Salassa, Dr. Marta Martínez Belmonte, Eduardo C. Escudero-Adán and Prof. Dr. Arjan W. Kleij

      Article first published online: 20 APR 2012 | DOI: 10.1002/chem.201200335

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      Host with the most! Supramolecular hosts based on bis-Zn(salphen) scaffolds have been prepared that allow for either monotopic or ditopic binding of suitable chiral guest molecules; this binding results in chirogenesis effects that can be programmed through rigidification of the host by simple cation addition. This new host has potential for the determination of the absolute configurations of various chiral substrates through either di- or monotopic binding modes.

    7. Acetoxy Migration

      Gold-Catalyzed 1,2-/1,2-Bis-acetoxy Migration of 1,4-Bis-propargyl Acetates: A Mechanistic Study (pages 6811–6824)

      Teresa de Haro, Prof. Dr. Enrique Gómez-Bengoa, Dr. Riccardo Cribiú, Dr. Xiaogen Huang and Prof. Dr. Cristina Nevado

      Article first published online: 4 APR 2012 | DOI: 10.1002/chem.201103472

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      Gold catalysis: The gold-catalyzed tandem 1,2-/1,2-bis-acetoxy migration of 1,4-bis-propargyl acetates stereoselectively affords 2,3-bis-acetoxy-1,3-dienes depending on the electronic and steric features of the ancillary ligand bound to gold and the substituents at the propargylic positions (see scheme). Computational studies have revealed the subtle mechanistic differences governing these transformations.

    8. Hydrogen Storage

      A New Ammine Dual-Cation (Li, Mg) Borohydride: Synthesis, Structure, and Dehydrogenation Enhancement (pages 6825–6834)

      Dr. Weiwei Sun, Xiaowei Chen, Dr. Qinfen Gu, Kia S. Wallwork, Yingbin Tan, Ziwei Tang and Prof. Xuebin Yu

      Article first published online: 11 APR 2012 | DOI: 10.1002/chem.201102651

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      Potential hydrogen-storage material: A new ammine double-cation borohydride, LiMg(BH4)3(NH3)2, shown by X-ray powder diffraction analysis to adopt a 3D network architecture, has been synthesized and investigated. Analysis of the synthesized LiMg(BH4)3(NH3)2/LiBH4 mixture showed that it exhibits dramatically improved dehydrogenation properties at relatively low temperatures and the release of high purity H2 (see figure).

    9. Hydrogen Bonds

      Quantifying Homo- and Heteromolecular Hydrogen Bonds as a Guide for Adduct Formation (pages 6835–6846)

      Dr. Amit Delori, Dr. Peter T. A. Galek, Dr. Elna Pidcock and Prof. William Jones

      Article first published online: 18 APR 2012 | DOI: 10.1002/chem.201103129

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      Ready, steady, go! Chemists working on drug molecules would benefit from being able to predict the likelihood of successes or failures in salt or co-crystal formation to prioritise experimental work. We have used the hydrogen bond propensity method (see figure) to predict the success of ten molecular adduct crystallisation reactions. The results show good agreement with the experimental observations.

    10. Photocatalysts

      Controlled Orientation in a Bio-Inspired Assembly of Ag/AgCl/ZnO Nanostructures Enables Enhancement in Visible-Light-Induced Photocatalytic Performance (pages 6847–6853)

      Dr. Gousia Begum, Joydeb Manna and Dr. Rohit Kumar Rana

      Article first published online: 16 APR 2012 | DOI: 10.1002/chem.201103760

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      It's easy being green: Oriented nanocomponents in Ag/AgCl/ZnO obtained by means of an environmentally benign bio-inspired approach, in which polyamines not only act as the mineralizing agent for ZnO, but also simultaneously facilitate the formation of Ag/AgCl under ambient conditions, further leads to enhanced photocatalytic activity under visible-light irradiation (see figure).

    11. Photochemistry

      You have full text access to this OnlineOpen article
      Unraveling the Mechanism of the Photodeprotection Reaction of 8-Bromo- and 8-Chloro-7-hydroxyquinoline Caged Acetates (pages 6854–6865)

      Jiani Ma, Adam C. Rea, Dr. Huiying An, Dr. Chensheng Ma, Dr. Xiangguo Guan, Dr. Ming-De Li, Tao Su, Chi Shun Yeung, Kyle T. Harris, Dr. Yue Zhu, Jameil L. Nganga, Dr. Olesya D. Fedoryak, Dr. Timothy M. Dore and Dr. David Lee Phillips

      Article first published online: 18 APR 2012 | DOI: 10.1002/chem.201200366

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      The water-mediated triplet excited state deprotection reaction of 8-bromo- and 8-chloro-7-hydroxyquinoline caged acetate (BHQ-OAc) in water-rich neutral solutions was investigated through photochemical product outcome studies and nanosecond time-resolved spectroscopic measurements. Combined with density functional theory calculations, a detailed photodeprotection mechanism in neutral aqueous solution was deduced (see scheme).

    12. Coordination Polymers

      Direct Crystallographic Observation of Catalytic Reactions inside the Pores of a Flexible Coordination Polymer (pages 6866–6872)

      Raj Kumar Das, Arshad Aijaz, Manish K. Sharma, Prem Lama and Prof. Dr. Parimal K. Bharadwaj

      Article first published online: 20 APR 2012 | DOI: 10.1002/chem.201200046

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      Rich man, pore man: Molecules inside confined environments can behave very differently to their bulk state owing to different reactivities. Both Knoevenagel condensation and cyanosilylation reactions were catalyzed by the confined space that was provided by a single coordination polymer. These processes were monitored in a single-crystal to single-crystal fashion (see figure).

    13. Stereocontrol

      Stereoselective Palladium-Catalyzed Functionalization of Homoallylic Alcohols: A Convenient Synthesis of Di- and Trisubstituted Isoxazolidines and β-Amino-δ-Hydroxy Esters (pages 6873–6884)

      Prof. Dr. Andrei V. Malkov, Dr. Maciej Barłóg, Dr. Lucie Miller-Potucká, Dr. Mikhail A. Kabeshov, Dr. Louis J. Farrugia and Prof. Dr. Pavel Kočovský

      Article first published online: 23 APR 2012 | DOI: 10.1002/chem.201102716

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      Syn-full cyclization! Enantiopure, Boc-protected alkoxyamines undergo a diastereoselective Pd-catalyzed ring-closing carbonylative amidation to produce isoxazolidines (≤50:1 d.r.) that can be readily converted into the N-Boc-protected esters of β-amino-δ-hydroxy acids and their γ-substituted homologues (see scheme). The key carbonylative cyclization proceeds through an unusual syn addition of the palladium and the nitrogen nucleophile across the C[DOUBLE BOND]C bond.

    14. Asymmetric Synthesis

      Scaffold-Inspired Enantioselective Synthesis of Biologically Important Spiro[pyrrolidin-3,2′-oxindoles] with Structural Diversity through Catalytic Isatin-Derived 1,3-Dipolar Cycloadditions (pages 6885–6894)

      Feng Shi, Zhong-Lin Tao, Shi-Wei Luo, Prof. Shu-Jiang Tu and Prof. Liu-Zhu Gong

      Article first published online: 13 APR 2012 | DOI: 10.1002/chem.201200358

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      The organocatalytic approach: The first catalytic asymmetric construction of a spiro[pyrrolidin-3,2′-oxindole] scaffold with contiguous quaternary stereogenic centers in excellent stereoselectivities has been established (see scheme). This protocol represents the first example of catalytic asymmetric 1,3-dipolar cycloadditions involving azomethine ylides generated in situ from unsymmetrical cyclic ketones.

    15. Carbohydrates

      Stereoselective Synthesis of α- and β-Glycofuranosyl Amides by Traceless Ligation of Glycofuranosyl Azides (pages 6895–6906)

      Dr. Filippo Nisic, Gaetano Speciale and Prof. Dr. Anna Bernardi

      Article first published online: 19 APR 2012 | DOI: 10.1002/chem.201200309

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      Without a trace: A highly stereoselective synthesis of both α- and β-glycofuranosyl amides based on the traceless Staudinger ligation of glycofuranosyl azides of the galacto, ribo, and arabino series with 2-diphenylphosphanyl-phenyl esters is reported (see scheme). The process does not depend on the anomeric configuration of the starting azide, but appears to be controlled by the C2 configuration and by the protection/deprotection state of the substrates.

    16. Stereochemistry

      Palladium-Catalyzed Asymmetric Quaternary Stereocenter Formation (pages 6907–6914)

      Aditya L. Gottumukkala, Dr. Kiran Matcha, Dr. Martin Lutz, Prof. Dr. Johannes G. de Vries  and Prof. Dr. Adriaan J. Minnaard

      Article first published online: 24 APR 2012 | DOI: 10.1002/chem.201200694

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      Jack of all trades: An efficient Pd catalyst for the formation of benzylic quaternary stereocenters by conjugate addition of arylboronic acids to a variety of β,β-disubstituted cyclic and acyclic enones is presented (see scheme). The catalyst provides product enantioselectivities up to 99 %.

    17. Carbon Dioxide Activation

      Synthesis of PCP-Supported Nickel Complexes and their Reactivity with Carbon Dioxide (pages 6915–6927)

      Timothy J. Schmeier, Dr. Ainara Nova, Prof. Dr. Nilay Hazari and Prof. Dr. Feliu Maseras

      Article first published online: 23 APR 2012 | DOI: 10.1002/chem.201103992

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      CO2feeling the pinch: A number of different PCP-supported Ni pincer complexes have been synthesized and their reactions with CO2 studied by using both experiments and theory. CO2 insertion into Ni hydroxide, amide, and imidazole bonds is both kinetically and thermodynamically facile, whereas insertion into a Ni oxazole bond is thermodynamically favorable, but kinetically unfavorable, and insertion into Ni alkyne, azide, malonate, and cyanide bonds is thermodynamically unfavorable (see scheme).

    18. OLEDs

      Solution-Processed, Undoped, Deep-Blue Organic Light-Emitting Diodes Based on Starburst Oligofluorenes with a Planar Triphenylamine Core (pages 6928–6934)

      Cui Liu, Yanhu Li, Yingyue Zhang, Prof. Chuluo Yang, Prof. Hongbin Wu, Prof. Jingui Qin and Prof. Yong Cao

      Article first published online: 26 APR 2012 | DOI: 10.1002/chem.201200062

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      She's a star: Three starburst oligomers that have a rigid planar triphenylamine core and oligofluorene arms were synthesized (see figure). The undoped deep-blue OLED with T3 as the emitter showed a maximum current efficiency of 3.83 cd A−1 and a maximum external quantum efficiency of 4.19 % with CIE coordinates of (0.16, 0.09), which is among the highest values for undoped deep-blue OLEDs that are based on solution-processable conjugated starbursts.

    19. Ligand Effects

      Axial Ligand and Spin-State Influence on the Formation and Reactivity of Hydroperoxo–Iron(III) Porphyrin Complexes (pages 6935–6949)

      Dr. Alicja Franke, Dr. Christoph Fertinger and Prof. Dr. Rudi van Eldik

      Article first published online: 24 APR 2012 | DOI: 10.1002/chem.201103036

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      Uncovering the reactivity secret: The stability of hydroperoxo–iron(III) porphyrin complexes formed in the [FeIII(tpfpp)X]/H2O2/HOO system (TPFPP=5,10,15,20-tetrakis(pentafluorophenyl)-21H,23H-porphyrin; X=Cl or CF3SO3) was tuned by the selection of appropriate reaction conditions and their reactivity in the course of direct oxidation reactions was examined (see figure).

    20. Palladium Catalysis

      Control over the Chemoselectivity of Pd-Catalyzed Cyclization Reactions of (2-Iodoanilino)carbonyl Compounds (pages 6950–6958)

      Prof. Dr. Daniel Solé, Dr. Israel Fernández and Prof. Dr. Miguel A. Sierra

      Article first published online: 4 APR 2012 | DOI: 10.1002/chem.201102811

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      Pd-controlled! The chemoselectivity of Pd-catalyzed cyclization reactions of (2-iodoanilino)carbonyl compounds can be controlled by proper selection of the reactants, additives, and reaction conditions. These factors have a great impact on the key palladacycle intermediate (see scheme) from which the competitive reaction pathways (i.e., α-arylation versus nucleophilic addition) occur.

    21. Allylic Compounds

      Structures and Dynamic Solution Behavior of Cationic, Two-Coordinate Gold(I)–π-Allene Complexes (pages 6959–6971)

      Timothy J. Brown, Dr. Atsushi Sugie, Dr. Marina G. D. Leed and Prof. Ross A. Widenhoefer

      Article first published online: 23 APR 2012 | DOI: 10.1002/chem.201103289

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      Pot of gold: A family of cationic, two-coordinate gold–π-allene complexes was isolated and characterized by spectroscopy and in three cases by X-ray crystallography. Variable-temperature NMR analysis revealed fluxional behavior consistent with facile intramolecular exchange of the allene π-faces through η1-allene transition states and/or intermediates that retain a staggered arrangement of the allene substituents (see scheme).

    22. Graphene

      Highly Concentrated Aqueous Dispersions of Graphene Exfoliated by Sodium Taurodeoxycholate: Dispersion Behavior and Potential Application as a Catalyst Support for the Oxygen-Reduction Reaction (pages 6972–6978)

      Dr. Zhenyu Sun, Justus Masa, Prof. Dr. Zhimin Liu, Prof. Dr. Wolfgang Schuhmann and Prof. Dr. Martin Muhler

      Article first published online: 13 APR 2012 | DOI: 10.1002/chem.201103253

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      The great dispersion: Stable aqueous dispersions of pristine graphene were achieved by using the superior surfactant sodium taurodeoxycholate with the aid of tip sonication at very high concentrations (up to 7.1 mg mL−1). The dispersions have potential applications in conductive films and in highly active electrocatalysts (see figure).

    23. MOF Modification

      Post-Synthetic Modification of Zr-Metal–Organic Frameworks through Cycloaddition Reactions (pages 6979–6985)

      Dr. Pascal Roy, Andreas Schaate, Prof. Dr. Peter Behrens and Prof. Dr. Adelheid Godt

      Article first published online: 16 APR 2012 | DOI: 10.1002/chem.201103288

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      Modifying and disassembling MOFs: Porous interpenetrated Zr-organic frameworks (PIZOFs) with large pores have been post-synthetically modified through 1,3-dipolar cycloaddition and Diels–Alder reactions (see scheme, left). Additionally, a simple procedure is reported for the disassembly of the hydrolytically very stable UiO-66- and PIZOF-type Zr-based MOFs for analytical purposes (see scheme, right).

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      Preview: Chem. Eur. J. 23/2012 (page 6987)

      Article first published online: 23 MAY 2012 | DOI: 10.1002/chem.201290091

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