Angewandte Chemie International Edition

Cover image for Vol. 43 Issue 14

March 26, 2004

Volume 43, Issue 14

Pages 1747–1893

    1. Cover Picture: Excess Electron Transport Through DNA: A Single Electron Repairs More than One UV-Induced Lesion (Angew. Chem. Int. Ed. 14/2004) (page 1747)

      Bernd Giese, Barbara Carl, Thomas Carl, Thomas Carell, Christoph Behrens, Ulrich Hennecke, Olav Schiemann and Emiliano Feresin

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200490038

      Electron-catalyzed repair of thymine dimers in double-stranded DNA is described by B. Giese, T. Carell, O. Schiemann, and co-workers on page 1848 ff. Transport of an electron from a remote modified thymine base through DNA occurs in a multistep hopping process. When the electron meets a thymine dimer, which is generated by photocycloaddition of adjacent thymine residues, the two thymine bases are repaired through a retro-cyclization reaction, while the electron continues along the DNA.

    2. Recent Developments in the Catalytic Asymmetric Cyanation of Ketimines (pages 1764–1766)

      Claude Spino

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200301686

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      Contrasting styles: The two catalysts shown are both effective for the cyanation of ketimines. The metal-based catalyst 1, developed by a standard approach, displays a very broad scope and substrate generality. The metal-free catalyst 2 was designed by a combination of random screening and mechanism-based optimization.

    3. Stable Singlet Carbenes—Plentiful and Versatile (pages 1767–1769)

      Wolfgang Kirmse

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200301729

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      Electron donation from substituents is the principal mechanism of stabilizing singlet carbenes. Two amino groups are optimal (A). With additional steric protection, one amino group is sufficient (B). The effect of phosphanyl groups is enhanced by an electron acceptor as the second substituent (C).

    4. The Chemical Laboratory: Source of Progress or Chamber of Horrors? (pages 1770–1780)

      Otto Krätz

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200330064

      Must chemistry stink and go bang? The laboratory as a forbidding setting, as a workshop of extraordinary obscurantists whose sole unholy purpose is to produce all manner of poisons and acids, is a fond stereotype in literary fiction. Realistic descriptions are reserved exclusively for chemist writers. A foray through the literature shows that chemistry sometimes has a sinister public image.

    5. Agostic Interactions in d0 Metal Alkyl Complexes (pages 1782–1806)

      Wolfgang Scherer and G. Sean McGrady

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200200548

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      Bonding concepts: Agostic interactions in early-transition-metal alkyl complexes are reviewed, and shown to arise from delocalization of the M[BOND]C bond rather than through M⋅⋅⋅H[BOND]C bonding: charge-density analysis (see picture) reveals intimate aspects of the phenomenon and shows how the agostic interaction competes with other ligand-induced effects at the metal center.

    6. Synthesis and Characterization of Cross-Linked Conjugated Polymer Milli-, Micro-, and Nanoparticles (pages 1808–1811)

      Eric Hittinger, Akshay Kokil and Christoph Weder

      Version of Record online: 29 JAN 2004 | DOI: 10.1002/anie.200352863

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      The use of aqueous emulsions as the media when conducting cross-coupling reactions, instead of homogeneous solutions, produces covalently cross-linked conjugated polymer particles (see picture). The size of the spherical particles can easily be tuned over a wide range (mm to nm) by modification of the reaction conditions. The resulting materials are processable in the form of a suspension and promise to have interesting electronic properties.

    7. Potential Peptide Carriers: Amphipathic Proline-Rich Peptides Derived from the N-Terminal Domain of γ-Zein (pages 1811–1814)

      Jimena Fernández-Carneado, Marcelo J. Kogan, Susanna Castel and Ernest Giralt

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200352540

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      Breaking into cells: A new family of peptides based on the amphipathic proline-rich sequence (VXLPPP)n, where n=1–3 and X=His, Lys, or Arg, has been designed (see picture). Their nonviral origin, absence of toxicity at high concentrations, and high solubility in water make this new series very promising for use in drug delivery.

    8. Self-Assembly of a Spin-Coupled Octanuclear Copper(II) Circular Array from a Single-Stranded Ligand (pages 1814–1817)

      Stuart T. Onions, Sarah L. Heath, Daniel J. Price, Ross W. Harrington, William Clegg and Craig J. Matthews

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200352554

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      You're round and bound: A bowed arrangement of bridging bidentate binding sites on a ligand framework precludes a linear arrangement of metal ions. This conformation allows a spin-coupled octanuclear copper(II) circular array to be formed from a single-stranded ligand (see picture); this circular array displays weak ferromagnetic exchange between metal centers and is a rare example of such an array containing more than six centers.

    9. Old Clusters with New Tricks: Engineering S⋅⋅⋅S Interactions and Novel Physical Properties in Sulfite-Based Dawson Clusters (pages 1817–1820)

      De-Liang Long, Paul Kögerler and Leroy Cronin

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200352896

      Unprecedented 18-molybdosulfite Dawson clusters encapsulate two pyramidal sulfite ions as templates, and exhibit a short S⋅⋅⋅S interaction between the two ions, which was characterized by DFT calculations. The [Mo18O54(SO3)2]4− ion is the first discrete thermochromic polyoxometalate cluster: its color varies from pale yellow at 77 K to deep red at 500 K (see picture).

    10. Cyclophane-Based Highly Active Late-Transition-Metal Catalysts for Ethylene Polymerization (pages 1821–1825)

      Drexel H. Camacho, Eric V. Salo, Joseph W. Ziller and Zhibin Guan

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353226

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      Better by design: Exploitation of the macrocyclic architecture of a cyclophane-based ligand provides new highly active catalysts with improved thermal stability for ethylene polymerization. The strategic positioning of the metal center at the core of the cyclophane-based ligand is the key to the observed high activity and thermal stability, and to the high molecular weight of the polyethylene (see picture; red: Pd, green: Cl, blue: N, gray: C).

    11. A Porphyrin Nanotube: Size-Selective Inclusion of Tetranuclear Molybdenum–Oxo Clusters (pages 1825–1828)

      Ryosuke Harada, Yoshihisa Matsuda, Hisashi Ōkawa and Takahiko Kojima

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353325

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      Mo takes the tube: A saddle-distorted MoV–porphyrin complex forms a tubular assembly through intermolecular π–π interactions, which has an internal diameter of 1 nm (see picture). Within such tubes, tetranuclear MoVI–oxo clusters could be size-selectively included through intermolecular hydrogen-bonding interactions.

    12. A Robust Purely Organic Nanoporous Magnet (pages 1828–1832)

      Daniel Maspoch, Neus Domingo, Daniel Ruiz-Molina, Klaus Wurst, Gavin Vaughan, Javier Tejada, Concepció Rovira and Jaume Veciana

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353358

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      Holey magnets: A pure organic nanoporous material (POROF-2) exhibiting astonishing thermal stability, hydrophilic one-dimensional channels (see structure), and a long-range ferromagnetic ordering is prepared. This zeolite-like material is the first example of a purely organic robust open-framework magnet.

    13. Octalanthanide Wheels Supported by p-tert-Butylsulfonylcalix[4]arene (pages 1832–1835)

      Takashi Kajiwara, Hashen Wu, Tasuku Ito, Nobuhiko Iki and Sotaro Miyano

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353449

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      A cluster-forming ligand, p-tert-butylsulfonylcalix[4]arene (H4L), allows the formation of lanthanide wheels whose cluster cores contain eight lanthanide ions (GdIII, SmIII, NdIII, or PrIII; shown in green in the picture) connected by L4− ions, which act as both a tetradentate and a bisbidentate μ3-ligand, and eight bridging acetate groups. The wheels form by a “step-by-step” process via the mononuclear subunit {Ln(L)}.

    14. Assembling Dimeric π Stacks on Gold Surfaces by Using Three-Dimensional Lock-and-Key Receptors (pages 1836–1839)

      George S. Tulevski, Mark L. Bushey, Jenna L. Kosky, Shane J. T. Ruter and Colin Nuckolls

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353476

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      Nest building: a method to create a rigid hydrogen-bond receptor through the simultaneous binding of three thiol substituent groups to a gold surface is reported (see picture: red=O, gray=C, blue=N, yellow=S, purple=Au surface atom). These receptors are able to distinguish and select for π surfaces with a complementary size, shape, and hydrogen-bonding code.

    15. Criteria for Efficient Transport of Excess Electrons in DNA (pages 1839–1842)

      Takeo Ito and Steven E. Rokita

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353038

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      Better molecular wires could result from an improved understanding of the effects of nucleotide sequence on the efficiency of excess electron transfer in DNA. Negative charge migrates in duplex DNA from a photoexcited aromatic amine residue (D; see figure) to 5-bromo-2′-deoxyuridine (BrU) in a sequence- and orientation-dependent manner.

    16. Excess Electron Transfer Driven DNA Does Not Depend on the Transfer Direction (pages 1842–1844)

      Clemens Haas, Katja Kräling, Michaela Cichon, Nicole Rahe and Thomas Carell

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353067

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      DNA is a two-way street: Excess electron transfer in DNA over distances of 3.4–23.8 Å does not depend on the transfer direction, as shown by probing DNA:PNA hybrid double strands containing a cyclobutane pyrimidine dimer (T[DOUBLE BOND]T) and flavin (Fl; see figure).

    17. Phenanthridinium as an Artificial Base and Charge Donor in DNA (pages 1845–1847)

      Nicole Amann, Robert Huber and Hans-Achim Wagenknecht

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353153

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      A tool for time-resolved studies: The phenanthridinium unit of ethidium was incorporated into oligonucleotides (see scheme) as an artificial DNA base. The resulting duplexes can be used to study electron-transfer processes by spectroscopic techniques and to compare the rates of reductive electron transfer and oxidative hole transfer.

    18. Excess Electron Transport Through DNA: A Single Electron Repairs More than One UV-Induced Lesion (pages 1848–1851)

      Bernd Giese, Barbara Carl, Thomas Carl, Thomas Carell, Christoph Behrens, Ulrich Hennecke, Olav Schiemann and Emiliano Feresin

      Version of Record online: 9 MAR 2004 | DOI: 10.1002/anie.200353264

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      Site-selective injection of a single electron into thymine (yellow) through the modified nucleoside 1 (1[RIGHTWARDS ARROW]2) was used to examine the dependence of excess electron transfer in DNA on distance. The DNA was cleaved upon arrival of the electron at a thymine dimer (red). This assay showed that one electron can repair more than one UV-induced lesion in DNA 3.

    19. Non-Natural Eight-Connected Solid-State Materials: A New Coordination Chemistry (pages 1851–1854)

      De-Liang Long, Robert J. Hill, Alexander J. Blake, Neil R. Champness, Peter Hubberstey, Davide M. Proserpio, Claire Wilson and Martin Schröder

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200352625

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      Non-CsCl topologies for eight-connected solid-state materials have been observed for the first time in three networks based on lanthanide cations and 4,4′-bipyridine-N,N′-dioxide ligands. The structure of the {[Yb(L)4](CF3SO3)3} network is depicted.

    20. B-Octamethyl-[12]Mercuracarborand-4 as Host for “Naked” Fluoride Ions (pages 1854–1857)

      Michael J. Bayer, Satish S. Jalisatgi, Brian Smart, Axel Herzog, Carolyn B. Knobler and M. Frederick Hawthorne

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200352899

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      Fs in rings: A cyclic multidentate Lewis acidic receptor is coordinated by a weakly bonded fluoride ion in 1 (see picture). This host–guest system has properties such as air- and moisture-stability, solubility in common organic solvents, and utility as a source for “naked” fluoride ions generated in situ.

    21. Polyaddition and Polycondensation Reactions of (2-Furyl)carbenoid as Step-Growth Polymerization Strategies: Synthesis of Furylcyclopropane- and Furfurylidene-Containing Polymers (pages 1857–1860)

      Koji Miki, Yosuke Washitake, Kouichi Ohe and Sakae Uemura

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200352949

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      Polymers from carbenoid intermediates: A new approach to the synthesis of cyclopropane- and alkene-containing polymers that contain both a carbenoid donor and acceptor is described. The polymers can be effectively obtained from enyne ketones via carbenoid intermediates in the presence of a [{Rh(OAc)2}2] catalyst (see scheme).

    22. Phosphane-Free Rhodium Catalyst in an Anionic Micellar System for [4+2] Annulation of Dienynes (pages 1860–1862)

      Dai Motoda, Hidenori Kinoshita, Hiroshi Shinokubo and Koichiro Oshima

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353123

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      A highly active, cationic, phosphane-ligand-free rhodium species is formed in an aqueous anionic micellar system (see scheme). The combination of [{RhCl(nbd)}2]–sodium dodecyl sulfate acts as an effective catalyst for the intramolecular [4+2] annulation of 2,4-dienyl propargyl ethers in water (nbd=norbornadiene).

    23. Nanocapillary Arrays Effect Mixing and Reaction in Multilayer Fluidic Structures (pages 1862–1865)

      Tzu-C. Kuo, Hee-K. Kim, Donald M. Cannon Jr., Mark A. Shannon, Jonathan V. Sweedler and Paul W. Bohn

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353279

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      Reactant mixing is implemented in structures with characteristic length scales of nanometers (see picture). Mixing occurs within micron distances rather than the centimeters that are often needed for laminar microflows. The application of the nanocapillary mixer to detect Ca2+ ions demonstrates its potential use in sensors.

    24. Palladium-Catalyzed [3,3] Sigmatropic Rearrangement of (Allyloxy)iminodiazaphospholidines: Allylic Transposition of C[BOND]O and C[BOND]N Functionality (pages 1865–1868)

      Ernest E. Lee and Robert A. Batey

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353284

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      A PV[DOUBLE BOND]N to PV[DOUBLE BOND]O interconversion is the thermodynamic driving force for the title reaction. Iminodiazaphospholidines 1 give phosphoramides 2, which are subsequently hydrolyzed under mild acidic conditions to yield primary or tosylamines 3. R=alkyl, phenyl; Ts=p-toluenesulfonyl.

    25. Homolytic Cα[BOND]Cβ Bond Cleavage in a Chiral Alkylarene Radical Cation: Effects of Asymmetric Microsolvation (pages 1868–1871)

      Daniele Catone, Anna Giardini Guidoni, Alessandra Paladini, Susanna Piccirillo, Flaminia Rondino, Mauro Satta, Debora Scuderi and Maurizio Speranza

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353462

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      Fragmentation of the (R)-(+)-1-phenyl-1-propanol radical cation ([(BZC2H5)R]+) is markedly affected by asymmetric microsolvation (see picture). The Cα[BOND]Cβ bond cleavage in the heterochiral [(BZC2H5)R.BDSS]+ cluster is more efficient than in the homochiral [(BZC2H5)R.BDRR]+. The difference is ascribed to structural factors that make BDSS a better H-bond acceptor than BDRR in their adducts with [(BZC2H5)R]+. BZ=PhCHOH, BD=2,3-butanediol.

    26. A Rationally Designed Universal Catalyst for Suzuki–Miyaura Coupling Processes (pages 1871–1876)

      Shawn D. Walker, Timothy E. Barder, Joseph R. Martinelli and Stephen L. Buchwald

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353615

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      Unprecedented scope, reactivity, and stability are displayed by a new catalyst system. This was demonstrated with general and efficient syntheses of sterically hindered (hetero)biaryls (see examples shown), mild coupling reactions of alkyl boron derivatives, and rapid coupling reactions of aryl chlorides at room temperature.

    27. Heterolytic Cleavage of H2 at a Sulfur-Bridged Dinuclear Ruthenium Center (pages 1877–1880)

      Dieter Sellmann, Raju Prakash, Frank W. Heinemann, Matthias Moll and Maria Klimowicz

      Version of Record online: 9 MAR 2004 | DOI: 10.1002/anie.200453717

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      Incoming molecular hydrogen breaks the Ru[BOND]S bridges in the diruthenium complex [Ru(pybuS4)]2 (pybuS42−=2,6-bis(2-sulfanyl-3,5-di-tert-butylphenylthio)dimethylpyridine(2−)) shown, and the H[BOND]H bond is cleaved to give H+ and H in the resulting thiol-protonated hydride [Ru(H)(pybuS4-H)]. The proposed mechanism of the heterolytic cleavage of H2 at the Ru[BOND]S centers is intriguing and possibly relevant to the activation of H2 by hydrogenases.

    28. In Situ Generation of Highly Active Dissolved Palladium Species from Solid Catalysts—A Concept for the Activation of Aryl Chlorides in the Heck Reaction (pages 1881–1882)

      Sandra S. Pröckl, Wolfgang Kleist, Markus A. Gruber and Klaus Köhler

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353473

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      Needing a leach: Optimized palladium/metal oxide systems are highly active heterogeneous catalysts for the Heck reaction. Non-activated and deactivated aryl chlorides can be converted by palladium/zeolite (NaY) catalysts (see scheme). The dissolution of palladium (leaching) from the surface of the support, its redeposition, and the control of these equilibria are found to be crucial for the success of the reaction.

    29. Unusual Pulvinic Acid Dimers from the Common Fungi Scleroderma citrinum (Common Earthball) and Chalciporus piperatus (Peppery Bolete) (pages 1883–1886)

      Monika Winner, Alberto Giménez, Helga Schmidt, Bernd Sontag, Bert Steffan and Wolfgang Steglich

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200352529

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      What do some fungi have in common with chemists? Common earthballs (see picture) and peppery boletes are true artists in natural product synthesis. In few biosynthetic steps they assemble structurally fascinating alicyclic pigments from simple aromatic precursors.

    30. Prebiotic Formation of Amino Acids in a Neutral Atmosphere by Electric Discharge (pages 1886–1888)

      Kristof Plankensteiner, Hannes Reiner, Benjamin Schranz and Bernd Michael Rode

      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200353135

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      On the way to life, the formation of amino acids on the primordial earth was one of the essential prerequisites. To date, this formation could only be explained assuming a reducing atmosphere, which according to contemporary geochemistry could not have existed. Simulating a neutral primitive CO2/N2/H2O atmosphere above liquid water with frequent electric discharges (see picture) provides a model for the formation of peptides, and thus proteins and ultimately life.

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      Version of Record online: 24 MAR 2004 | DOI: 10.1002/anie.200490040