Chemistry - A European Journal

Cover image for Vol. 19 Issue 12

March 18, 2013

Volume 19, Issue 12

Pages 3777–4077

  1. Cover Pictures

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    1. You have free access to this content
      Cover Picture: Asararenes—A Family of Large Aromatic Macrocycles (Chem. Eur. J. 12/2013) (page 3777)

      Dr. Severin T. Schneebeli, Chuyang Cheng, Dr. Karel J. Hartlieb, Nathan L. Strutt, Dr. Amy A. Sarjeant, Dr. Charlotte L. Stern and Prof. J. Fraser Stoddart

      Article first published online: 8 MAR 2013 | DOI: 10.1002/chem.201390037

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      A component of ginger namely, 1,2,4,5-tetramethoxybenzene, when heated in 1,2-dichloroethane, along with paraformaldehyde in the presence of boron trifluoride etherate, has spawned a new family of aromatic macrocycles, called asararenes. The cover image produced by Aleksandr Bosoy shows the X-ray superstructure of asar[10]arene. The individual macrocycles comprising this asararene stack to form cylindrical nanotube-like channels packed together in a regular checkerboard array. Just as cyclodextrins and cucurbiturils, for example, have become household names and major players in supramolecular chemistry, materials science and molecular nanotechnology, so could the asararenes in the fullness of time. For more details, see the Full Paper by J. F. Stoddart et al. on page 3860 ff.

    2. You have free access to this content
      Back Cover: Solid-State Structural Transformations and Photoreactivity of 1D-Ladder Coordination Polymers of PbII (Chem. Eur. J. 12/2013) (page 4080)

      Dr. Goutam Kumar Kole, Dr. Abdul Malik Puthan Peedikakkal, Belinda Mei Fang Toh and Prof. Dr. Jagadese J. Vittal

      Article first published online: 8 MAR 2013 | DOI: 10.1002/chem.201390040

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      One-dimensional coordination polymers (CPs) containing ladder structures are ideal to conduct [2+2] cycloaddition reactions. While attempting to align the bis(4′-pyridyl)ethylene ligand pairs using PbII and three different benzoate anions, linear photostable CPs were obtained with a hydrogen-bonded water chain in the lattice as a kinetic product. On removal of the lattice water, the polymers rearrange to a ladder structure. One of the three ladder structures synthesized undergoes a single-crystal-to-single-crystal photochemical reaction to give the cyclobutane-containing coordination polymer as described in the Full Paper by J. J. Vittal on page 3962 ff. The backgournd photo is the 2nd Howrah bridge, Kolkata (India).

  2. Graphical Abstract

    1. Top of page
    2. Cover Pictures
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    1. Graphical Abstract: Chem. Eur. J. 12/2013 (pages 3780–3788)

      Article first published online: 8 MAR 2013 | DOI: 10.1002/chem.201390038

  3. News

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

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

      Glycosylated Nanoscale Surfaces: Preparation and Applications in Medicine and Molecular Biology (pages 3794–3800)

      Dr. David C. Kennedy, Dan Grünstein, Dr. Chian-Hui Lai and Prof. Dr. Peter H. Seeberger

      Article first published online: 18 FEB 2013 | DOI: 10.1002/chem.201204155

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      The sweet spot of nanomedicine: Carbohydrates are key to cellular signalling pathways and major contributors to molecular recognition events at the cell surface. Novel nanomaterials that probe multivalent binding events between carbohydrates and their biological binding partners are driving discovery at this interface (see figure).

  5. Communications

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

      Streamlined Catalytic Asymmetric Synthesis of Atorvastatin (pages 3802–3806)

      Yuji Kawato , Dr. Sandeep Chaudhary, Dr. Naoya Kumagai and Prof. Dr. Masakatsu Shibasaki 

      Article first published online: 21 FEB 2013 | DOI: 10.1002/chem.201204609

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      An efficient enantioselective synthetic route to atorvastatin was developed based on a direct catalytic asymmetric aldol reaction. The expensive chiral ligand used in the initial aldol reaction was readily recovered (91 %) and reused. Implementation of an oxy-Michael reaction for the construction of the syn-1,3-diol unit eliminated several redundant steps, allowing for rapid access to the common intermediate in six steps (see scheme).

    2. Peptidomimetics

      Synthesis of a 6,6-Spiroketal Amino Acid and Its Incorporation into a Peptide Turn Sequence Using Solid-Phase Peptide Synthesis (pages 3807–3811)

      Jui Thiang Brian Kueh, Dr. Ka Wai Choi, Dr. Geoffrey M. Williams, Dr. Kerstin Moehle, Dr. Bernadett Bacsa, Prof. John A. Robinson and Prof. Margaret A. Brimble

      Article first published online: 19 FEB 2013 | DOI: 10.1002/chem.201204546

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      Spiropins for SPPS: The rigid structure of an anomerically stabilised spiroketal motif enables the appendage of substituents in a fixed conformation. To assess the ability of a spiroketal motif to induce a turn structure and participate in solid-phase peptide synthesis (SPPS), an Fmoc-spiroketal amino acid was synthesised and incorporated into a spiroketal-containing cyclic peptide (see figure).

    3. Electrocyclization

      A New Access to 4 H-Quinolizines from 2-Vinylpyridine and Alkynes Promoted by Rhodium–N-Heterocyclic-Carbene Catalysts (pages 3812–3816)

      Ramón Azpíroz, Dr. Andrea Di Giuseppe, Dr. Ricardo Castarlenas, Prof. Jesús J. Pérez-Torrente and Prof. Luis A. Oro

      Article first published online: 21 FEB 2013 | DOI: 10.1002/chem.201300236

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      Forging the lock that autolocks! Rh[BOND]NHC catalysts promote a new access to 4 H-quinolizine species from 2-vinylpyridine and terminal and internal alkynes through C[BOND]H activation and C[BOND]C coupling reactions (see figure). N-Bridgehead heterocycle formation is favored for internal- over terminal-substituted butadienylpyridine derivatives in a thermal 6π-electrocyclization process.

    4. Cycloisomerization

      Poly(ethylene glycol) as a Reaction Matrix in Platinum- or Gold-Catalyzed Cycloisomerization: A Mechanistic Investigation (pages 3817–3821)

      Dr. Rosella Spina, Dr. Evelina Colacino, Prof. Jean Martinez and Dr. Frédéric Lamaty

      Article first published online: 18 FEB 2013 | DOI: 10.1002/chem.201203800

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      Design for diversity: A new catalytic system based on PEG-3400 and a metal salt (Pt or Au) was designed to efficiently perform a cycloisomerization reaction under microwave irradiation, which gave diverse heterocycles in good to excellent yields, after a precipitation/filtration procedure (see scheme).

    5. Quantum Dots

      Graphene Quantum Dots Combined with Europium Ions as Photoluminescent Probes for Phosphate Sensing (pages 3822–3826)

      Jian-Mei Bai, Dr. Li Zhang, Prof. Ru-Ping Liang and Prof. Jian-Ding Qiu

      Article first published online: 18 FEB 2013 | DOI: 10.1002/chem.201204295

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      The sense of it: A new type of rapid, sensitive, and specific photoluminescence (PL)-based assay has been proposed for the detection of phosphate (Pi) based on the competition of oxygen-donor atoms from Pi with those from the carboxylate groups on a graphene-quantum-dot (GQD) surface for Eu3+ ions (see scheme). The graphene-like structures combined with QD-like optical properties suggest the promising nature of the GQDs as versatile tools in the fields of analytical science and biotechnology.

    6. Reaction Mechanisms

      Mechanism of the Methyltrioxorhenium-Catalyzed Deoxydehydration of Polyols: A New Pathway Revealed (pages 3827–3832)

      Shuanglin Qu, Yanfeng Dang, Mingwei Wen and Prof. Dr. Zhi-Xiang Wang

      Article first published online: 18 FEB 2013 | DOI: 10.1002/chem.201204001

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      Polyols pathway probed: Density functional theory computations reveal that the methyltrioxorhenium-catalyzed deoxydehydration of polyols follows pathway C, which is energetically more favorable than the previously proposed pathways A and B (see scheme). In addition to serving as solvent/reductant, the alcohol also acts as a shuttle to greatly facilitate various hydrogen-transfer steps.

    7. C[BOND]H Activation

      Titanium-Catalyzed Intermolecular Hydroaminoalkylation of Conjugated Dienes (pages 3833–3837)

      Till Preuß, Wolfgang Saak and Prof. Dr. Sven Doye

      Article first published online: 20 FEB 2013 | DOI: 10.1002/chem.201203693

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      Ti me kangaroo down: Conjugated dienes undergo intermolecular hydroaminoalkylation in the presence of Ti catalyst [Ind2TiMe2] (Ind=η5-indenyl). This new reaction offers a highly atom-efficient approach to homoallylic amines from 1,3-butadienes.

    8. Asymmetric Catalysis

      Highly Diastereo- and Enantioselective Cross-Cascade Reactions of Different Enones (pages 3838–3841)

      Huicai Huang, Wenbin Wu, Kailong Zhu, Juan Hu and Prof. Dr. Jinxing Ye

      Article first published online: 20 FEB 2013 | DOI: 10.1002/chem.201204520

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      Cascading ketones! The first highly efficient asymmetric cross-cascade reaction of different α,β-unsaturated ketones catalyzed by an easily prepared bulky primary amine salt has been developed. It affords the corresponding diverse products containing three to four contiguous stereocenters with excellent enantio- and diastereoselectivities (see scheme).

    9. Cascade Reactions

      β-Siloxy-α-haloketones through Highly Diastereoselective Single and Double Mukaiyama Aldol Reactions (pages 3842–3845)

      Dr. Jakub Saadi and Prof. Dr. Hisashi Yamamoto

      Article first published online: 19 FEB 2013 | DOI: 10.1002/chem.201204493

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      Double-action haloketones: A super silyl group enabled the first highly diastereoselective Mukaiyama aldol reactions of α-chloro- and α-fluoroketones with a wide range of aldehydes, providing anti-β-siloxy-α-haloketones. This process is compatible with one-pot double-aldol methodology and allows for rapid access to new halogen-modified polyketide fragments bearing up to four contiguous stereocenters (see scheme).

  6. Full Papers

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

      Probing the Different Life Stages of a Fluid Catalytic Cracking Particle with Integrated Laser and Electron Microscopy (pages 3846–3859)

      Matthia A. Karreman, Dr. Inge L. C. Buurmans, Dr. Alexandra V. Agronskaia, Prof. Dr. John W. Geus, Prof. Dr. Hans C. Gerritsen and Prof. Dr. Bert M. Weckhuysen

      Article first published online: 27 FEB 2013 | DOI: 10.1002/chem.201203491

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      Exposing the cracks: Several processes in an industrial fluid catalytic cracking (FCC) unit lead to deactivation of FCC particles. A structural and functional analysis of hydrothermally deactivated FCC particles and particles from a commercial equilibrium catalyst particle (ECat) sample was performed. A model is postulated for the degradation of the zeolite component. Inter- and intraparticle distributions of defects were mapped, resulting in the identification of a rim of fully deactivated zeolites (see figure).

    2. Supramolecular Chemistry

      Asararenes—A Family of Large Aromatic Macrocycles (pages 3860–3868)

      Dr. Severin T. Schneebeli, Chuyang Cheng, Dr. Karel J. Hartlieb, Nathan L. Strutt, Dr. Amy A. Sarjeant, Dr. Charlotte L. Stern and Prof. J. Fraser Stoddart

      Article first published online: 18 FEB 2013 | DOI: 10.1002/chem.201204097

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      Gingering up macrocycles: Asarol methyl ether (1,2,4,5-tetramethoxybenzene), a component of ginger, reacts with paraformaldehyde in the presence of BF3⋅OEt2 to produce a new family of macrocycles. Solid-state structures of asar[6]-, asar[7]-, asar[8]-, asar[9]-, asar[10]- and asar[11]arene shed light on the conformational behavior of this new family of potential receptors, which could find applications in materials science and the life sciences in the fullness of time.

    3. Fluorination

      Chiral Fluorinated α-Sulfonyl Carbanions: Enantioselective Synthesis and Electrophilic Capture, Racemization Dynamics, and Structure (pages 3869–3897)

      Dr. Gunther Hellmann, Dr. Achim Hack, Dr. Eric Thiemermann, Dr. Olaf Luche, Prof. Dr. Gerhard Raabe and Prof. Dr. Hans-Joachim Gais

      Article first published online: 10 FEB 2013 | DOI: 10.1002/chem.201204014

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      Worth their salt: Chiral Li α-(S)-trifluoromethylsulfonyl carbanion salts with ≥98 % enantiomeric excess (ee) and high configurational stability are accessible through the reaction of chiral triflones (≥98 % ee) with RLi (see figure). Their electrophilic capture occurs with high enantioselectivity. Studies of the structure and dynamics of chiral Li α-(S)-trifluoromethylsulfonyl carbanion salts revealed monomeric contact ion pairs.

    4. Aromaticity

      Azatrioxa[8]circulenes: Planar Anti-Aromatic Cyclooctatetraenes (pages 3898–3904)

      Dr. Christian B. Nielsen, Dr. Theis Brock-Nannestad, Dr. Peter Hammershøj, Dr. Theis K. Reenberg, Dr. Magnus Schau-Magnussen, Denis Trpcevski, Thomas Hensel, Dr. Roberto Salcedo, Gleb V. Baryshnikov, Prof. Boris F. Minaev and Dr. Michael Pittelkow

      Article first published online: 10 FEB 2013 | DOI: 10.1002/chem.201203113

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      Planar cyclooctatetraenes: The first synthesis of a new class of anti-aromatic planar cyclooctatetraenes is described: the azatrioxa[8]circulenes (see scheme). The azatrioxa[8]circulenes were fully characterised by using optical, electrochemical and computational techniques as well as by single-crystal X-ray crystallography. The aromatic/anti-aromatic nature of the planar cyclooctatetraenes is discussed and compared with the isoelectronic tetraoxa[8]circulenes.

    5. Hydrogen Activation

      Proton-Assisted Hydrogen Activation on Polyhedral Cations (pages 3905–3912)

      Beatriz Calvo, Dr. Ramón Macías, Maria Jose Artigas, Dr. Fernando J. Lahoz and Prof. Dr. Luis A. Oro

      Article first published online: 10 FEB 2013 | DOI: 10.1002/chem.201203925

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      Keeping active: Protonation of closo-rhodathioboranes affords unusual cationic clusters with enhanced Lewis acidity and remarkable lability. Protonation of compound 1 with triflic acid prompts an ionic equilibrium that efficiently splits H2 (see scheme).

    6. Glycopeptides

      Microwave-Assisted Solid-Phase Synthesis of Antifreeze Glycopeptides (pages 3913–3920)

      Dr. Ryukou Izumi, Dr. Takahiko Matsushita, Dr. Naoki Fujitani, Dr. Kentaro Naruchi, Dr. Hiroki Shimizu, Dr. Sakae Tsuda, Dr. Hiroshi Hinou and Prof. Dr. Shin-Ichiro Nishimura

      Article first published online: 10 FEB 2013 | DOI: 10.1002/chem.201203731

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      Antifreeze glycopeptides: A rapid and efficient microwave-assisted solid-phase synthesis of tandem repeating glycopeptides is reported (see figure) that has allowed a structural and functional characterization of monodispersed antifreeze glycopeptide analogs (degree of polymerization=2–6).

    7. Metalloproteins

      On the Design of Zinc-Finger Models with Cyclic Peptides Bearing a Linear Tail (pages 3921–3931)

      Aurélie Jacques, Bastien Mettra, Vincent Lebrun, Dr. Jean-Marc Latour and Dr. Olivier Sénèque

      Article first published online: 21 FEB 2013 | DOI: 10.1002/chem.201204167

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      Versatile design: Model peptides for various zinc-finger fold types can be created by using cyclic peptides with a linear tail (CPLT; see figure). We discuss the properties of CPLT and their advantages over linear peptides for zinc-finger modeling, and we propose some rules for the successful design of small metalloprotein models based on CPLT.

    8. Gold Catalysis

      Synthesis of gem-Diaurated Species from Alkynols (pages 3932–3942)

      Alexander Zhdanko and Prof. Dr. Martin E. Maier

      Article first published online: 11 FEB 2013 | DOI: 10.1002/chem.201204491

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      Catch the gold fish: A number of enol ether derived diaurated species were synthesized directly from different alkynols and cationic gold complexes in the presence of a non-nucleophilic base (proton sponge; see scheme). The reaction can be easily applied for the in situ generation of diaurated species from all common types of hydroalkoxylation substrates: 5-endo, 5-exo/6-endo, 6-exo/7-endo and even intermolecular types. The reactivity of various gold oxo compounds (LAu)2OH+, (LAu)3O+, and LAuOH (L=phosphine ligand) towards alkynols was also examined.

    9. Single-Molecule Magnets

      A New Family of Trinuclear Nickel(II) Complexes as Single-Molecule Magnets (pages 3943–3953)

      Rituparna Biswas, Yumi Ida, Dr. Michael L. Baker, Saptarshi Biswas, Paramita Kar, Prof. Dr. Hiroyuki Nojiri, Prof. Dr. Takayuki Ishida and Prof. Dr. Ashutosh Ghosh

      Article first published online: 30 JAN 2013 | DOI: 10.1002/chem.201202795

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      Nickel(II) magnets: A new family of trinuclear NiII complexes with phenoxido (μ2 and μ3), hydroxido (μ3), and μ2-Cl, μ1,1-NCO, or μ1,1-N3 bridges have been prepared that form face-sharing coordination polyhedra (see figure). The three complexes exhibit a dominant ferromagnetic exchange coupling with sizable uniaxial anisotropy. The slow magnetization relaxation, the hysteresis of the pulsed-field magnetization, a magnetic easy axis, and the high-frequency EPR spectra show that these complexes constitute a new class of single-molecule magnets.

    10. Computational Chemistry

      Are β-H-Eliminations or Alkene Insertions Feasible Elementary Steps in Catalytic Cycles Involving Gold(I) Alkyl Species or Gold(I) Hydrides? (pages 3954–3961)

      Dr. Günter Klatt, Dr. Rong Xu, Dr. Markus Pernpointner, Lise Molinari, Tran Quang Hung, Dr. Frank Rominger, Prof. Dr. A. Stephen K. Hashmi and Prof. Dr. Horst Köppel

      Article first published online: 10 FEB 2013 | DOI: 10.1002/chem.201203043

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      AuI reactions out of reach: A β-H elimination in an (iPr)Au-alkyl complex or an alkene insertion at an (iPr)AuH complex proceed through high-energy transition states and thus are inaccessible for gold catalysis (see figure).

    11. Solid-State Reactions

      Solid-State Structural Transformations and Photoreactivity of 1D-Ladder Coordination Polymers of PbII (pages 3962–3968)

      Dr. Goutam Kumar Kole, Dr. Abdul Malik Puthan Peedikakkal, Belinda Mei Fang Toh and Prof. Dr. Jagadese J. Vittal

      Article first published online: 18 FEB 2013 | DOI: 10.1002/chem.201203678

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      Dehydrate to be photoactive! The solid-state structural transformation of a linear coordination polymer of PbII into the corresponding ladder coordination polymer (see figure) and a single-crystal-to-single-crystal [2+2] cycloaddition reaction under UV light are reported.

    12. Speciation Studies

      Speciation of [Cp*2M2O5] in Polar and Donor Solvents (pages 3969–3985)

      Dr. Pelin Sözen-Aktaş, Dr. Iker Del Rosal, Dr. Eric Manoury, Prof. Funda Demirhan, Prof. Agustí Lledós and Prof. Rinaldo Poli

      Article first published online: 10 FEB 2013 | DOI: 10.1002/chem.201203075

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      Origin of species: Compounds [Cp*2M2O5] (M=Mo, W; Cp*=pentamethylcyclopentadienyl; see figure) reveal a rich and complex speciation chemistry in polar protic and aprotic solvents, yielding various species including [Cp*MO2(solv)]+, [Cp*MO2(OR)] (R=H, Me), and [Cp*MO3] depending on the nature of the solvent and on the amount of water present.

    13. Rare Earths

      Discrete Divalent Rare-Earth Cationic ROP Catalysts: Ligand-Dependent Redox Behavior and Discrepancies with Alkaline-Earth Analogues in a Ligand-Assisted Activated Monomer Mechanism (pages 3986–3994)

      Dr. Bo Liu, Dr. Thierry Roisnel, Prof. Dr. Laurent Maron, Prof. Dr. Jean-François Carpentier and Dr. Yann Sarazin

      Article first published online: 5 FEB 2013 | DOI: 10.1002/chem.201204340

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      In rare form: The first stable, solvent-free, cationic divalent rare-earth complexes are reported. The divalent Yb and Eu complexes are structurally related to their alkaline-earth (Ca, Sr) congeners, but display specific reactivity of their own and yield highly competent and redox-stable catalysts for the controlled immortal ring-opening polymerization (iROP) of cyclic esters and carbonates following a ligand-assisted activated monomer mechanism (see scheme).

    14. Antigens

      Total Synthesis of the Escherichia coli O111 O-Specific Polysaccharide Repeating Unit (pages 3995–4002)

      Oliviana Calin, Dr. Steffen Eller, Heung Sik Hahm and Prof. Dr. Peter H. Seeberger

      Article first published online: 27 FEB 2013 | DOI: 10.1002/chem.201204394

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      Killing them sweetly: As a first step towards diagnostics and vaccines to detect and prevent serious infections with Escherichia coli bacteria, the pentasaccharide repeating unit from the O-antigen of E. coli O111 was synthesized.

    15. Iridium Complexes

      Reactivity Studies of Iridium Pyridylidenes [TpMe2Ir(C6H5)2(C(CH)3C(R)NH] (R=H, Me, Ph) (pages 4003–4020)

      Crispín Cristóbal, Dr. Yohar A. Hernández, Dr. Joaquín López-Serrano, Prof. Dr. Margarita Paneque, Dr. Ana Petronilho, Prof. Dr. Manuel L. Poveda, Dr. Verónica Salazar, Florencia Vattier, Dr. Eleuterio Álvarez, Dr. Celia Maya and Prof. Dr. Ernesto Carmona

      Article first published online: 11 FEB 2013 | DOI: 10.1002/chem.201203818

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      Sweet 16 e: Many pyridylidenes 1 react with a diverse range of reagents via 16 e phenyl[BOND]pyridyl intermediates A (see scheme), which, in general, behave as internally frustrated Lewis pairs (FLPs).

    16. Reaction Mechanisms

      Fast Reductive Amination by Transfer Hydrogenation “on Water” (pages 4021–4029)

      Qian Lei, Yawen Wei, Dinesh Talwar, Prof. Chao Wang, Prof. Dong Xue and Prof. Jianliang Xiao

      Article first published online: 10 FEB 2013 | DOI: 10.1002/chem.201204194

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      Greener amine synthesis: A versatile reductive amination protocol has been developed. By using an iridium catalyst in water, a broad range of ketones and aldehydes react with amines to afford various new amines in good yields (see scheme), with molar ratios of the substrate to the catalyst (S/C) as high as 1×105. The pH of the reaction solution plays a key role, regulating both the catalytic activity and the selectivity.

    17. Alcohol Amination

      Artificial Multi-Enzyme Networks for the Asymmetric Amination of sec-Alcohols (pages 4030–4035)

      Katharina Tauber, Michael Fuchs, Johann H. Sattler, Julia Pitzer, Desiree Pressnitz, Dr. Dominik Koszelewski, Prof. Kurt Faber, Jan Pfeffer, Thomas Haas and Prof. Wolfgang Kroutil

      Article first published online: 22 JAN 2013 | DOI: 10.1002/chem.201202666

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      Trickle-down effect: The asymmetric amination of sec-alcohols to the corresponding α-chiral primary amines was performed with a biocatalytic cascade whereby the various steps were interconnected through the cofactors/cosubstrates. In a redox-neutral cascade and under optimised conditions, up to 91 % conversion of an alcohol to the amine was achieved.

    18. Bioorthogonal Reactions

      Rapid and Specific Post-Synthesis Modification of DNA through a Biocompatible Condensation of 1,2-Aminothiols with 2-Cyanobenzothiazole (pages 4036–4042)

      Dr. Yunfeng Cheng, Dr. Hanjing Peng, Dr. Weixuan Chen, Dr. Nanting Ni, Dr. Bowen Ke, Dr. Chaofeng Dai and Prof. Binghe Wang

      Article first published online: 28 FEB 2013 | DOI: 10.1002/chem.201201677

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      The first enzymatic incorporation of a cyanobenzothiazole (CBT)-modified thymidine has been developed. The side-chain handle CBT can undergo a rapid and site-specific cyclization reaction with 1,2-aminothiols to enable DNA functionalization in aqueous solution. A key advantage of this method is the formation of a single stereo/regioisomer in the process, which allows for precise control of DNA modification to yield a single component (see scheme).

    19. Gold Catalysis

      Gold-Catalyzed Annulations of 2-Alkynyl Benzaldehydes with Vinyl Ethers: Synthesis of Dihydronaphthalene, Isochromene, and Bicyclo[2.2.2]octane Derivatives (pages 4043–4050)

      Deepika Malhotra, Dr. Le-Ping Liu, Dr. Mark S. Mashuta and Prof. Dr. G. B. Hammond

      Article first published online: 30 JAN 2013 | DOI: 10.1002/chem.201203841

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      The (mild) Midas touch: The gold-catalyzed reactions of 2-alkynyl benzaldehydes with acyclic or cyclic vinyl ethers afforded acetal-tethered dihydronaphthalene 1, isochromene 2, and bicyclo[2.2.2]octane 3 under mild reaction conditions (see scheme). Plausible mechanisms for the formations of these interesting compounds are discussed.

    20. Supramolecular Chemistry

      Co-Conformational Isomerism in a Neutral Ion-Paired Supramolecular System (pages 4051–4057)

      Dr. Ruy Cervantes, Raul I. Sánchez and Prof. Jorge Tiburcio

      Article first published online: 22 JAN 2013 | DOI: 10.1002/chem.201203483

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      Threaded or not threaded? It is possible to separate counter-ion effects from structural preferences in association complexes by isolating neutral ion-paired supramolecular systems. Two different co-conformational isomers have been observed in solution and in the solid state by using a viologen guest and a dianionic crown ether host (see figure).

    21. High-Valent Metal–Oxo Complexes

      Does Hydrogen-Bonding Donation to Manganese(IV)–Oxo and Iron(IV)–Oxo Oxidants Affect the Oxygen-Atom Transfer Ability? A Computational Study (pages 4058–4068)

      Dr. Reza Latifi, Mala A. Sainna, Prof. Elena V. Rybak-Akimova and Dr. Sam P. de Visser

      Article first published online: 30 JAN 2013 | DOI: 10.1002/chem.201202811

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      Density functional theory calculations are presented on hydrogen-atom abstraction reactions by nonheme iron(IV)–oxo oxidants with distal hydrogen-bonding interactions. We show that the hydrogen bonding restricts substrate approach and that it also raises the BDEOH value, thereby making it a poorer oxidant. The work has been rationalized to heme and nonheme iron enzymes and it is proposed that distal hydrogen bonding restricts the properties of the enzyme and lowers its oxidative power.

    22. Density Functional Calculations

      On the Mechanism of the Dehydroaromatization of Hexane to Benzene by an Iridium Pincer Catalyst (pages 4069–4077)

      Akanksha Thawani, Dr. Ramanan Rajeev and Prof. Dr. Raghavan B. Sunoj

      Article first published online: 31 JAN 2013 | DOI: 10.1002/chem.201204062

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      On the right path: A comprehensive mechanistic picture for the formation of benzene from hexane, catalyzed by an iridium pincer complex, was obtained by using density functional computations. The preferred pathway involves the formation of hex-1-ene through C1[BOND]H-bond activation of hexane, hexa-1,3-diene, and hexa-1,3,5-triene. Finally, electrocyclization of the resultant triene to cyclohexadiene was followed by dehydroaromatization to benzene (see scheme).

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