Angewandte Chemie International Edition

Cover image for Vol. 44 Issue 12

March 11, 2005

Volume 44, Issue 12

Pages 1741–1893

    1. Cover Picture: Methane and Carbon Dioxide Storage in a Porous van der Waals Crystal (Angew. Chem. Int. Ed. 12/2005) (page 1741)

      P. Sozzani, S. Bracco, A. Comotti, L. Ferretti and R. Simonutti

      Version of Record online: 8 MAR 2005 | DOI: 10.1002/anie.200590036

      Like a swarm of bees who find shelter in the hexagonal cells of the beehive, CH4 and CO2 molecules are stabilized by weak CH⋅⋅⋅π interactions within the open-pore van der Waals crystals of tris-o-phenylenedioxycyclotriphosphazene. The supramolecular network is sufficiently robust to store a large number of gas molecules. In their Communication on page 1816 ff., P. Sozzani et al. describe the absorption properties of the crystals and the spectroscopic observation of gases trapped in the nanochannels.

    2. Protonated Chiral Catalysts: Versatile Tools for Asymmetric Synthesis (pages 1758–1763)

      Carsten Bolm, Toni Rantanen, Ingo Schiffers and Lorenzo Zani

      Version of Record online: 8 MAR 2005 | DOI: 10.1002/anie.200500154

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      Acid treatment: Exposure of catalytically inactive (neutral) molecules to strong Brønsted acids generates cationic species (e.g. 1 and 2) that catalyze a wide range of synthetically powerful transformations. These reactions give products with excellent ee values. TfO=trifluoromethanesulfonate; TFA=trifluoroacetic acid.

    3. Molecular Recognition in Organic Crystals: Directed Intermolecular Bonds or Nonlocalized Bonding? (pages 1766–1787)

      Jack D. Dunitz and Angelo Gavezzotti

      Version of Record online: 31 JAN 2005 | DOI: 10.1002/anie.200460157

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      Recognising recognition: In describing intermolecular recognition, conventional wisdom often relies on weak bonds between individual atoms in different molecules, rather than considering less-localized interactions between molecular electron densities (see picture). A proposal is made to abandon the traditional view of a molecule as an array of atoms, in favor of an electron-cloud picture. The new computational tool pixel is used to calculate the intermolecular energies from the electron density of the isolated molecules.

    4. Orthogonal Multipolar Interactions in Structural Chemistry and Biology (pages 1788–1805)

      Ralph Paulini, Klaus Müller and François Diederich

      Version of Record online: 11 FEB 2005 | DOI: 10.1002/anie.200462213

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      Types and structural features of noncovalent, multipolar interactions between intrinsically polar molecular functional groups are analyzed by using crystallographic-database mining. The results are discussed on the basis of scatterplot correlations of geometrical parameters. The picture shows a section of a complex of human transthyretin with flufenamic acid which displays three noncovalent polar C[BOND]F⋅⋅⋅C[DOUBLE BOND]O contacts.

    5. White-Light Emission from an Assembly Comprising Luminescent Iridium and Europium Complexes (pages 1806–1810)

      Paolo Coppo, Marco Duati, Valery N. Kozhevnikov, Johannes W. Hofstraat and Luisa De Cola

      Version of Record online: 13 DEC 2004 | DOI: 10.1002/anie.200461953

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      Red, white, and blue: White light was obtained by partial energy transfer (∂ET) between a blue-emitting IrIII–phenylpyridine complex and a red-emitting EuIII–terpyridine chelate through excitation of the assembly that is formed from the two metal complexes (see picture).

    6. Discrete Stacking of Large Aromatic Molecules within Organic-Pillared Coordination Cages (pages 1810–1813)

      Michito Yoshizawa, Junichi Nakagawa, Kazuhisa Kumazawa, Muneki Nagao, Masaki Kawano, Tomoji Ozeki and Makoto Fujita

      Version of Record online: 16 FEB 2005 | DOI: 10.1002/anie.200462171

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      Metal-hinged, organic-pillared cages accommodate a limited number (n) of π-stacked molecules in the cavity (see scheme): Discrete n+2 aromatic stacking occurs by the accommodation of n large aromatic guests (n=1–3). Owing to efficient donor–acceptor (D–A) interactions, A–D–A (n=1), A–D–D–A (n=2), and A–D–A–D–A (n=3) stacks are observed, which bring about even–odd-number effects in the UV/Vis absorption spectra.

    7. Tunable Imaging of Cells Labeled with MRI-PARACEST Agents (pages 1813–1815)

      Silvio Aime, Carla Carrera, Daniela Delli Castelli, Simonetta Geninatti Crich and Enzo Terreno

      Version of Record online: 21 FEB 2005 | DOI: 10.1002/anie.200462566

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      Cell-tracking experiments by MRI are possible with a novel class of Tb and Eu paramagnetic imaging agents, with which contrast is generated upon irradiation at a specific frequency (see picture). Middle: A) unlabeled; B) Tb-labeled; C) Eu-labeled; D) Tb- and Eu-labeled cells. Left: irradiation at ±180 kHz (Tb-agent-specific). Right: irradiation at ±15 kHz (Eu-agent-specific).

    8. Methane and Carbon Dioxide Storage in a Porous van der Waals Crystal (pages 1816–1820)

      P. Sozzani, S. Bracco, A. Comotti, L. Ferretti and R. Simonutti

      Version of Record online: 20 JAN 2005 | DOI: 10.1002/anie.200461704

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      Molecular gas jars: Methane and carbon dioxide can be stored in open-pore van der Waals crystals of tris-o-phenylenedioxycyclotriphosphazene at low partial pressure, whereas hydrogen, nitrogen, and oxygen are selectively excluded. Gas molecules participate in the supramolecular network of weak interactions and reside in the tight nanochannels in close contact with the surrounding aromatic rings (see picture).

    9. Preparation of Chiral Surfaces from Achiral Molecules by Controlled Symmetry Breaking (pages 1821–1823)

      Ava M. Berg and David L. Patrick

      Version of Record online: 14 FEB 2005 | DOI: 10.1002/anie.200461833

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      Chiral control without chirality: The adsorption of achiral liquid-crystal molecules to graphite substrates can generate surfaces with controlled enantiomeric excess and absolute chirality in the presence of a magnetic field, which assists in orienting the molecules. Unlike conventional approaches for chiral control, no chiral inputs are needed.

    10. CO Oxidation on Rutile-Supported Au Nanoparticles (pages 1824–1826)

      Ioannis N. Remediakis, Nuria Lopez and Jens K. Nørskov

      Version of Record online: 14 FEB 2005 | DOI: 10.1002/anie.200461699

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      What makes inert gold active? The answer lies in controlling the structure of Au particles at the nanoscale: Either many interface sites or many low-coordinate Au atoms need to be present in the particles. This principle is demonstrated by modeling the oxidation of CO on a rutile (TiO2)-supported Au nanocluster, the transition state of which does not involve the titania support (see picture: Au yellow, Ti light gray, C dark gray, O red).

    11. Cooperative Catalysis by General Acid and Base Bifunctionalized Mesoporous Silica Nanospheres (pages 1826–1830)

      Seong Huh, Hung-Ting Chen, Jerzy W. Wiench, Marek Pruski and Victor S.-Y. Lin

      Version of Record online: 11 FEB 2005 | DOI: 10.1002/anie.200462424

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      A team effort: Mesoporous silica nanosphere (MSN) materials bifunctionalized with a general acid group and a base group in various relative concentrations are described and shown to function as cooperative catalytic systems. The turnover numbers observed indicate that the acid groups can activate substrates in cooperation with the base groups to catalyze reactions that involve carbonyl activation (see picture).

    12. Going Beyond the Physical: Instilling Chirality onto the Electronic Structure of a Metal (pages 1830–1833)

      Andrew Mulligan, Ian Lane, Gilles B. D. Rousseau, Shona M. Johnston, David Lennon and Malcolm Kadodwala

      Version of Record online: 16 FEB 2005 | DOI: 10.1002/anie.200462265

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      Look below the surface: An adsorbed chiral molecule, 1-(1-naphthyl)ethylamine, reversibly instills chirality onto the electronic structure of a copper surface (see picture), a previously unobserved phenomenon. Conveying chirality onto the electronic structure of a metal surface is a possible mechanism by which chemical reactivity and electrical properties may be made chirally dependent.

    13. One-Dimensional Assembly of Lipophilic Inorganic Nanoparticles Templated by Peptide-Based Nanofibers with Binding Functionalities (pages 1833–1836)

      Liang-shi Li and Samuel I. Stupp

      Version of Record online: 18 FEB 2005 | DOI: 10.1002/anie.200462142

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      Good as gold: Nanofibers with surface hydrogen-bonding motifs co-assembled from peptide-based amphiphilic molecules were used to template one-dimensional assemblies of preformed lipophilic inorganic nanoparticles in apolar organic solvents (see figure).

    14. A Functional Model of the Cytochrome c Oxidase Active Site: Unique Conversion of a Heme–μ-peroxo–CuII Intermediate into Heme– superoxo/CuI (pages 1836–1840)

      Jin-Gang Liu, Yoshinori Naruta and Fumito Tani

      Version of Record online: 18 FEB 2005 | DOI: 10.1002/anie.200462582

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      Axial ligation of the heme moiety by a proximal imidazole group is observed in a novel cytochrome c oxidase (CcO) active-site model 1 in which the copper ion is bound to a N-(2-hydroxyphenyl)imidazole moiety. Spectroscopic observations of 1 suggest the unique transformation of an initial heme–μ-peroxo–CuII species into a heme–superoxide/CuI intermediate in the course of the CcO oxygenation reaction at low temperature.

    15. The Indium-Mediated Selective Introduction of Allenyl and Propargyl Groups at the C4-Position of 2-Azetidinones and the AuCl3-Catalyzed Cyclization of 4-Allenyl-2-azetidinones (pages 1840–1843)

      Phil Ho Lee, Heechul Kim, Kooyeon Lee, Misook Kim, Kwanghyun Noh, Hyunseok Kim and Dong Seomoon

      Version of Record online: 16 FEB 2005 | DOI: 10.1002/anie.200462512

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      Bicyclic β lactams are obtained by the two-step procedure shown in the scheme. Alternatively, with the help of organoindium reagents, allenyl and propargyl groups are introduced at the C4-position of 2-azetidinones. R1=H, 1R-(tert-butyldimethylsilyloxy)ethyl (TBSO(CH3)CH); R2=H, methyl, ethyl, n-butyl, phenyl, THPOCH2, trimethylsilyl, 2-naphthyl; R3=H, methyl, phenyl; R4=H, methyl.

    16. Sphere Currents of Buckminsterfullerene (pages 1843–1846)

      Mikael P. Johansson, Jonas Jusélius and Dage Sundholm

      Version of Record online: 11 FEB 2005 | DOI: 10.1002/anie.200462348

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      Global currents: Quantum chemical methodology has been used to investigate the magnetically induced currents of both neutral Buckminsterfullerene and its spherically aromatic +10 ion and has allowed quantitative measurement of the current strengths. Global sphere currents (see picture), instead of local ring currents, are found to be the defining feature of fullerene aromaticity.

    17. Trifluoromethylated Endohedral Metallofullerenes: Synthesis and Characterization of Y@C82(CF3)5 (pages 1846–1849)

      Ivan E. Kareev, Sergey F. Lebedkin, Vyacheslav P. Bubnov, Eduard B. Yagubskii, Ilya N. Ioffe, Pavel A. Khavrel, Igor V. Kuvychko, Steven H. Strauss and Olga V. Boltalina

      Version of Record online: 18 FEB 2005 | DOI: 10.1002/anie.200461497

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      Quantum chemical calculations and NMR spectroscopic data suggest that the two isomers of Y@C82(CF3)5 prepared by trifluoromethylation of the endohedral metallofullerene (EMF) contain chains of four 1,4-C6(CF3)2 edge-sharing hexagons (see picture). In striking contrast to the empty fullerenes, which form complex mixtures with up to 22 CF3 groups, EMF Y@C82 only forms products with one, three, and five CF3 groups.

    18. Synthesis of Hexa- and Dodecanuclear Organoaluminum Ring Structures Incorporating the “Magic” Ph2C(X) Group (X=O, NH) (pages 1850–1853)

      Carl Redshaw, Mark R. J. Elsegood and Kathryn E. Holmes

      Version of Record online: 18 FEB 2005 | DOI: 10.1002/anie.200461627

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      The magic touch! By using the “magic” group Ph2C(X) (X=O, NH), aluminum ring systems such as 1 have been synthesized from trimethylaluminum. For diphenylglycine (X=NH), both six- and twelve-membered rings have been structurally identified.

    19. Total Synthesis of Caprazol, a Core Structure of the Caprazamycin Antituberculosis Antibiotics (pages 1854–1856)

      Shinpei Hirano, Satoshi Ichikawa and Akira Matsuda

      Version of Record online: 18 FEB 2005 | DOI: 10.1002/anie.200462439

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      TB and anti-TB: Two key steps in the synthesis of caprazol (1), a core structure of the antituberculosis antibiotics, are the introduction of an aminoribose moiety by β-selective ribosylation without the use of neighboring-group participation and the construction of the diazepanone moiety.

    20. A Doubly N-Fused Benzohexaphyrin and Its Rearrangement to a Fluorescent Macrocycle upon DDQ Oxidation (pages 1856–1860)

      Yasuhide Inokuma, Takahiro Matsunari, Noboru Ono, Hidemitsu Uno and Atsuhiro Osuka

      Version of Record online: 21 FEB 2005 | DOI: 10.1002/anie.200462815

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      A retro-Diels–Alder reaction of a β-bicyclo[2.2.2]octadiene-fused precursor yields the doubly N-fused β-benzo[28]hexaphyrin( shown, which undergoes oxidative rearrangement upon treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to yield a macrocycle that emits fluorescence in the visible/near-IR region.

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      Polyazide Chemistry: The First Binary Group 6 Azides, Mo(N3)6, W(N3)6, [Mo(N3)7], and [W(N3)7], and the [NW(N3)4] and [NMo(N3)4] Ions (pages 1860–1865)

      Ralf Haiges, Jerry A. Boatz, Robert Bau, Stefan Schneider, Thorsten Schroer, Muhammed Yousufuddin and Karl O. Christe

      Version of Record online: 21 FEB 2005 | DOI: 10.1002/anie.200462740

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      Bang on target: The highly explosive Group 6 azides Mo(N3)6 and W(N3)6 are prepared by the reaction of Me3SiN3 with MoF6 and WF6, respectively. The structure of W(N3)6 has perfect rhombohedral C3 symmetry (see picture). The reaction of Mo(N3)6 and W(N3)6 with ionic azides leads to the formation of [Mo(N3)7] and [W(N3)7], respectively, the first binary heptaazides. Controlled decomposition of these anions produces [NMo(N3)4] and [NW(N3)4].

    22. Oxazoline-Mediated Interannular Cyclopalladation of Ferrocene: Chiral Palladium(II) Catalysts for the Enantioselective Aza-Claisen Rearrangement (pages 1865–1869)

      Albert Moyano, Malgorzata Rosol, Rosa M. Moreno, Concepción López and Miguel A. Maestro

      Version of Record online: 18 FEB 2005 | DOI: 10.1002/anie.200462434

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      Formation of a carbon–palladium bond to the unsubstituted cyclopentadiene ring occurs during the cyclopalladation of 4-ferrocenyl-1,3-oxazolines and leads to a new type of metalated ferrocene (see scheme). These chiral complexes catalyze the asymmetric aza-Claisen rearrangement of allylic imidates.

    23. Synthesis of Medium-Ring and Iodinated Biaryl Compounds by Organocuprate Oxidation (pages 1870–1873)

      David S. Surry, Xianbin Su, David J. Fox, Vilius Franckevicius, Simon J. F. Macdonald and David R. Spring

      Version of Record online: 9 FEB 2005 | DOI: 10.1002/anie.200462642

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      A biaryl banquet! Biphenyls with four ortho substituents, heteroaromatic compounds, iodinated biaryls, and medium rings containing biaryls are all readily synthesized by organocuprate oxidation. The utility of this new methodology is illustrated by the efficient synthesis of the medium-ring core of sanguiin H-5 (see scheme).

    24. Consecutive Vinylic to Aryl to Allylic Palladium Migration and Multiple C[BOND]H Activation Processes (pages 1873–1875)

      Jian Zhao, Marino Campo and Richard C. Larock

      Version of Record online: 14 FEB 2005 | DOI: 10.1002/anie.200462327

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      “Through-space” migration of palladium between remote carbon atoms appears to take place in the generation of π-allyl–palladium complexes, which are useful intermediates in organic synthesis. The reaction of halogenated arenes with alkynes under Pd-migration conditions provides the mixture of allylic esters AC (see reaction shown; X=Br, I; R1=H, OMe, CO2Et, Cl; R2=Ph, tBu).

    25. Very Large Ising-Type Magnetic Anisotropy in a Mononuclear NiII Complex (pages 1876–1879)

      Guillaume Rogez, Jean-Noël Rebilly, Anne-Laure Barra, Lorenzo Sorace, Geneviève Blondin, Nadeschda Kirchner, Marc Duran, Joris van Slageren, Simon Parsons, Louis Ricard, Arnaud Marvilliers and Talal Mallah

      Version of Record online: 11 FEB 2005 | DOI: 10.1002/anie.200462294

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      Complementarity between different techniques (magnetization, HF-HFEPR, FDMRS) and angular-overlap-model calculations allow the precise determination of the spin-Hamiltonian parameters in an isolated octahedral NiII complex (see structure), which exhibits the largest easy axis magnetic anisotropy reported to date (D=−10.1 cm−1, E/|D|=0.02).

    26. Resolution of [4]Heterohelicenium Dyes with Unprecedented Pummerer-like Chemistry (pages 1879–1883)

      Benoît Laleu, Pierre Mobian, Christelle Herse, Bo W. Laursen, Gérard Hopfgartner, Gérald Bernardinelli and Jérôme Lacour

      Version of Record online: 11 FEB 2005 | DOI: 10.1002/anie.200462321

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      Addition of an enantiopure sulfoxide auxiliary is the key to the resolution of highly stable [4]helicenium dyes. This transformation allows a facile chromatographic separation of the diastereomers (the structure of one such diastereomer is shown; S yellow, O red, N blue). Then an unprecedented Pummerer-like C[BOND]C bond fragmentation takes place to release the enantiopure cations.

    27. Carbon–Sulfur Bond Formation between a Ruthenium-Coordinated Thiyl Radical and Methyl Ketones (pages 1883–1887)

      Selma Poturovic, Mark S. Mashuta and Craig A. Grapperhaus

      Version of Record online: 11 FEB 2005 | DOI: 10.1002/anie.200462713

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      A metal-coordinated thiyl radical was revealed by the electrochemical oxidation of a ruthenium(III)–thiolate in acetone (and related ketones). The subsequent reaction between the radical intermediate and acetone resulted in C[BOND]S bond formation and ultimately a ruthenium(III)–thioether product (see picture). A mechanism that involves reaction of the enol tautomer of acetone with the radical is proposed.

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