Angewandte Chemie International Edition

Cover image for Vol. 43 Issue 11

March 5, 2004

Volume 43, Issue 11

Pages 1309–1441

    1. Cover Picture: Emergence of Morphological Chirality from Twinned Crystals (Angew. Chem. Int. Ed. 11/2004) (page 1309)

      Hiroaki Imai and Yuya Oaki

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200490029

      The helical morphology shown in the cover picture, emerges from triclinic crystals through diffusion-limited growth. The backbone of the helical architecture comprises twisted twins of the tilted subunit crystal originating from the triclinic system. The results provide a fundamental basis for the formation of various helical morphologies that have already been reported. For more information see the Communication by H. Imai and Y. Oaki on page 1363 ff.

    2. Catalyzed Reactions of Acyl Anion Equivalents (pages 1326–1328)

      Jeffrey S. Johnson

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200301702

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      More than century after the description of the benzoin condensation, chemists are developing new approaches toward and new reactions involving aldehyde umpolung. This chemistry has been recently expressed in aldehyde/ketone benzoin condensations, aldehyde/imine couplings, and enantioselective benzoin (B) and Stetter (A) reactions (see scheme; M = K, Na, Bu4N; Y = S, NR; Z = CH, N; X=alkoxy, alkyl).

    3. Coulomb Explosions and Stability of Multiply Charged Ions in the Gas Phase (pages 1329–1331)

      Detlef Schröder

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200301728

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      Stopping ions from going to pieces: Multiply charged molecular ions have fascinating bonding schemes which must counterbalance the strong Coulomb repulsion of the charge centers. In molecular-beam experiments it has been possible to generate small multiply charged anions, such as [Cr(SCN)4]2−, and analyze their fragmentation behavior (see scheme).

    4. Nanotubes by Template Wetting: A Modular Assembly System (pages 1334–1344)

      Martin Steinhart, Ralf B. Wehrspohn, Ulrich Gösele and Joachim H. Wendorff

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200300614

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      The spectrum of materials for nanotube walls can be broadened considerably by the simple and versatile technique of wetting porous templates. This opens up numerous possibilities for the functionalization of both porous membranes and individual nanotubes. These can be made from precious metals (see the scanning electron microscope image of a cross section of a Pd nanotube), high-performance polymers, or ferroelectric oxides, and exhibit nanotube walls with a specific fine structure.

    5. Oxidative Metalation of Azuliporphyrins with Copper(II) Salts: Formation of a Porphyrin Analogue System with a Unique Fully Conjugated Nonaromatic Azulene Subunit (pages 1346–1349)

      Denise A. Colby, Gregory M. Ferrence and Timothy D. Lash

      Version of Record online: 27 JAN 2004 | DOI: 10.1002/anie.200353189

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      Abnormal upfield shifts for the external azulene protons are seen in the 1H NMR spectra on oxidation of azuliporphyrins with copper(II) acetate to give highly distorted copper(II) complexes (see structure, brown Cu, blue N, red O, green H). These undergo demetalation with 10 % trifluoroacetic acid/chloroform to give unique cross-conjugated ketones.

    6. Kinetic and Thermodynamic Control by Chemical Bond Rearrangement on a Si(001) Surface (pages 1349–1352)

      Chiho Hamai, Akihiko Takagi, Masateru Taniguchi, Takuya Matsumoto and Tomoji Kawai

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352074

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      Changing the force: The driving force that determines the product distribution for acetone adsorbed on the Si(001) surface can be changed from kinetic (producing a four-member-ring species; see scheme) to thermodynamic (producing the dissociation species) upon raising the surface temperature. The results show that the binding of organic molecules to the Si(001) surface is in fact reversible.

    7. Covalently Attached Monolayers on Hydrogen-Terminated Si(100): Extremely Mild Attachment by Visible Light (pages 1352–1355)

      Qiao-Yu Sun, Louis C. P. M. de Smet, Barend van Lagen, Andrew Wright, Han Zuilhof and Ernst J. R. Sudhölter

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352137

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      An extremely mild and practical method to attach organic monolayers on flat silicon surfaces by using visible light (447 nm; see scheme) was developed and the mechanism investigated. With high-resolution angle-resolved X-ray photoelectron spectroscopy (ARXPS) depth profiles of the elements in the monolayer (≈2 nm thickness) were obtained.

    8. Modular Assembly of Glycoproteins: Towards the Synthesis of GlyCAM-1 by Using Expressed Protein Ligation (pages 1355–1359)

      Derek Macmillan and Carolyn R. Bertozzi

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352673

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      Put the two together: Physiologically relevant glycoproteins containing saccharides at predetermined sites, such as GlyCAM-1, can be generated from small synthetic and bacterially derived fragments by using the expressed protein ligation methodology. This technique was used for the synthesis of three semisynthetic GlyCAM-1 variants 13 (see scheme).

    9. Absolute Helical Arrangement of Stacked Benzene Rings: Heterogeneous Double-Helical Interaction Comprising a Hydrogen-Bonding Belt and an Offset Parallel Aromatic–Aromatic-Interaction Array (pages 1360–1363)

      Isao Azumaya, Daisuke Uchida, Takako Kato, Akihiro Yokoyama, Aya Tanatani, Hiroaki Takayanagi and Tsutomu Yokozawa

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352788

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      A resolution revolution? Self-assembled chiral structures resulting from the formation of two different helical interactions are found in the crystal structures of the achiral compound 1. The interactions give rise to Ar[BOND]H⋅⋅⋅π and OH⋅⋅⋅O[DOUBLE BOND]C arrays. The chirality of the helices is spontaneously resolved within individual single crystals. Only one of the hydroxy groups contributes to the formation of a helical hydrogen-bonding array (shown in green).

    10. Emergence of Morphological Chirality from Twinned Crystals (pages 1363–1368)

      Hiroaki Imai and Yuya Oaki

      Version of Record online: 27 JAN 2004 | DOI: 10.1002/anie.200352891

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      Twisted twins of subunit inorganic crystals make up the backbone of helical morphologies. Chirality emerges from crystals that are without molecular chirality through the assembly of tilted subunits under diffusion-limited conditions (see picture).

    11. Single-Crystal Adsorbents: A New Observation Field for Light Aggregates (pages 1368–1371)

      Satoshi Takamizawa, Ei-ichi Nakata and Teruo Saito

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352982

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      A convenient method to generate single-crystal clathrates involves placing a single-crystal adsorbent into a gaseous guest atmosphere (see picture; Rh magenta, O red, C and H gray, N blue). The procedure has the potential for producing numerous low-dimensional aggregate crystals, and should be most effective for observing specific quantum effects in a variety of low-dimensional systems.

    12. M4H4X: Hydrometals (M=Cu, Ni) Containing Tetracoordinate Planar Nonmetals (X=B, C, N, O) (pages 1371–1373)

      Si-Dian Li, Guang-Ming Ren, Chang-Qing Miao and Zhi-Hao Jin

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200353068

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      The first theoretical evidence for tetracoordinate planar nonmetals hosted at the centers of square hydrometal complexes M4H4X (M=Cu, Ni; X=B, C, N, O; see picture) has been obtained by ab initio calculations. These predictions may open a new branch of chemistry of nonmetal-centered hydrometals with potential applications as catalysts.

    13. Formation of Two-Dimensional Supramolecular Icelike Layer Containing (H2O)12 Rings (pages 1374–1376)

      Bao-Qing Ma, Hao-Ling Sun and Song Gao

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200353097

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      Water rings: Two novel water chains and layers have been observed in supramolecular solid states. The structures can be interconverted by varying crystallization conditions. The water layer consisting of fused (H2O)12 rings (see structure, O red, H blue) resembles ice Ih.

    14. Observation and Dynamics of “Charge-Transfer Isomers” (pages 1376–1381)

      Tasuku Ito, Naoyuki Imai, Tadashi Yamaguchi, Tomohiko Hamaguchi, Casey H. Londergan and Clifford P. Kubiak

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200353221

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      Upon electrochemical reduction, asymmetrically substituted dimers of Ru3 clusters [Ru3O(OAc)6(L)(CO)(μ-pz)Ru3O(OAc)6(L′)(CO)] (pz=pyrazine, L and L′ are N ligands), exhibit IR spectral line coalescence in the νCO region. The IR spectra suggest the existence of two possible “charge-transfer isomers” for example, [A–B] and [A–B], in which A and B represent different Ru3 moieties.

    15. Highly Antimalaria-Active Artemisinin Derivatives: Biological Activity Does Not Correlate with Chemical Reactivity (pages 1381–1385)

      Richard K. Haynes, Wing-Yan Ho, Ho-Wai Chan, Burkhard Fugmann, Jörg Stetter, Simon L. Croft, Livia Vivas, Wallace Peters and Brian L. Robinson

      Version of Record online: 16 FEB 2004 | DOI: 10.1002/anie.200352343

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      New leads for antimalarial drugs? 10-Alkylaminoartemisinin derivatives like that shown display in vivo antimalarial activities greater than those of the parent artemisinin. Previous conclusions regarding the chemical basis for the antimalarial activity of these compounds must be reconsidered.

    16. Molecular Motion of Endohedral Fullerenes in Single-Walled Carbon Nanotubes (pages 1386–1389)

      Andrei N. Khlobystov, Kyriakos Porfyrakis, Mito Kanai, David A. Britz, Arzhang Ardavan, Hisanori Shinohara, T. John S. Dennis and G. Andrew D. Briggs

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352389

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      Rock and roll: Endohedral fullerenes Ce@C82 inserted in single-walled carbon nanotubes (SWNTs) interact by electrostatic interactions and exhibit unusual dynamic behavior. Translational oscillations and discontinuous molecular rotations are observed (by high-resolution transmission electron microscopy) for the first time for molecular arrays inside SWNTs (see picture; blue dot=endohedral Ce atom). The fullerene rotation rate is different for isolated and aggregated nanotubes.

    17. Preparation of Shell Cross-Linked Micelles by Polyelectrolyte Complexation (pages 1389–1392)

      Jonathan V. M. Weaver, Yiqing Tang, Shiyong Liu, Peter D. Iddon, Rachel Grigg, Norman C. Billingham, Steven P. Armes, Robert Hunter and Steven P. Rannard

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352428

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      Shell shock: Shell cross-linked (SCL) micelles (3) are prepared by polyelectrolyte complexation by using a micelle-forming cationic ABC triblock copolymer (1) in conjunction with an anionic diblock copolymer cross-linker (2). This ionic cross-linking approach involves polymeric reagents that form physical complexes rapidly in aqueous solution at ambient temperature. Moreover, the product is surprisingly tolerant to added electrolyte.

    18. Electron Exchange Along the Tercyclopentadienyltrimetallic Scaffold: Kinetics, Equilibria, and Bond Strengths (pages 1393–1397)

      J. Kevin Cammack, Hani Amouri, Philip W. Leonard, Randy L. Myrabo and K. Peter C. Vollhardt

      Version of Record online: 9 FEB 2004 | DOI: 10.1002/anie.200352479

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      The metallomeric equilibrium between A and B can be quantified kinetically and thermodynamically by direct NMR techniques, which provide an insight into the mechanism of a fundamental organometallic displacement reaction and allows the estimation of relative metal–metal bond strengths in cyclopentadienyl–metal complexes (see scheme).

    19. Pd Nanoparticles Immobilized on Molecular Sieves by Ionic Liquids: Heterogeneous Catalysts for Solvent-Free Hydrogenation (pages 1397–1399)

      Jun Huang, Tao Jiang, Haixiang Gao, Buxing Han, Zhimin Liu, Weize Wu, Yanhong Chang and Guoying Zhao

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352682

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      A three-piece suite: The immobilization of a Pd-nanoparticle catalyst onto the surface of a molecular sieve by an ionic liquid (1,1,3,3-tetramethylguanidinium lactate) has been accomplished (see TEM image). The nanoparticle/ionic liquid/molecular sieve combination exhibits excellent synergistic effects that enhance the activity and durability of the catalyst for the hydrogenation of olefins.

    20. A Versatile Direct Approach to ortho-Substituted Azobenzenes from Benzotriazoles (pages 1400–1403)

      Xavier Àlvarez Micó, Thomas Ziegler and Lakshiminarayanapuram R. Subramanian

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352782

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      A new trump in the synthetic pack: The hidden potential of benzotriazoles to act as diazonium synthons has been witnessed in the reactions of 1-[(nonafluorobutyl)sulfonyl]-1H-1,2,3-benzotriazole with sodium phenoxide in which ortho-substituted azobenezenes were formed. The reaction can be steered towards ortho or para substitution simply by changing the solvent (this dichotomy is shown in an abstract fashion in the painting by Mathias Hansen).

    21. Formation of an Iron(II) Carbene–Thiolato Complex by Insertion of Carbon Monoxide into an Si[BOND]C Bond (pages 1404–1407)

      Masahiro Yuki, Tsukasa Matsuo and Hiroyuki Kawaguchi

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352916

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      Fischer carbenes – a new angle: The insertion of carbon monoxide into an Si[BOND]C bond of the FeII complex 1, which contains a tripodal thiolato ligand (see scheme), yields the Fischer carbene–thiolato complex 2, whose molecular structure reveals the presence of a bonding interaction between the carbene carbon atom and the thiolato sulfur atoms.

    22. Lipase-Catalyzed Domino Dynamic Kinetic Resolution of Racemic 3-Vinylcyclohex-2-en-1-ols/Intramolecular Diels–Alder Reaction: One-Pot Synthesis of Optically Active Polysubstituted Decalins (pages 1407–1410)

      Shuji Akai, Kouichi Tanimoto and Yasuyuki Kita

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200353044

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      Combining chemistry: The use of a lipase and a ruthenium catalyst allows the direct preparation of polysubstituted decalines with high optical and chemical yields from racemic alcohols (see scheme). The lipase-catalyzed kinetic resolution of the racemic alcohols, the ruthenium-catalyzed racemization of the slow-reacting enantiomers, and an intramolecular Diels–Alder reaction of the resultant esters all occur under identical conditions.

    23. Microwave-Assisted Synthesis of Single-Crystalline Tellurium Nanorods and Nanowires in Ionic Liquids (pages 1410–1414)

      Ying-Jie Zhu, Wei-Wei Wang, Rui-Juan Qi and Xian-Luo Hu

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200353101

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      HotMAIL! A microwave-assisted ionic-liquid (MAIL) method has been developed for controlled production of tellurium nanorods or nanowires (see pictures). The MAIL method is a fast, high-yield, and may be extended to synthesize a variety of other elemental and compound nanostructures.

    24. Direct Substitution of the Hydroxy Group in Alcohols with Silyl Nucleophiles Catalyzed by Indium Trichloride (pages 1414–1416)

      Makoto Yasuda, Takahiro Saito, Masako Ueba and Akio Baba

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200353121

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      Straightforward substitution: An excellent combination of a silyl nucleophile and indium catalyst was used to accomplish the dehydroxylation/alkylation of alcohols under nearly neutral conditions (see scheme, Si=silyl group) even though this type of reaction usually requires at least an equimolar amount of acid.

    25. Bimetallic Reagents of Silicon: One-Pot Synthesis of 2,3,5-Trisubstituted Tetrahydrofurans by a Double Sakurai–Hosomi Reaction (pages 1417–1419)

      Tarun K. Sarkar, Sk. Anwarul Haque and Arindrajit Basak

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200353184

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      Good yields and high stereoselectivities are found in the cyclization of 1-silylmethyl allylic silanes with aldehydes. The silanes act as bimetallic coupling reagents and effect cyclization to yield a variety of 2,3,5-trisubstituted tetrahydrofurans in a one-pot procedure. A three-component cyclization with only one product can also be achieved with this methodology (see scheme).

    26. Preparation and Structure of the First Germanium(II) Hydroxide: The Congener of an Unknown Low-Valent Carbon Analogue (pages 1419–1421)

      Leslie W. Pineda, Vojtech Jancik, Herbert W. Roesky, Dante Neculai and Ana M. Neculai

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200353205

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      Trapping HCl with an Arduengo-type carbene was the key to preparing and isolating the first germanium(II) hydroxide [LGeOH] (L=HC{(CMe)(2,6-iPr2C6H3N)}2) by hydrolysis of the corresponding chloride. In the solid state [LGeOH] forms dimers through an interaction of the OH group with the lone pair of another Ge atom (see picture; Ar=2,6-iPr2C6H3).

    27. Highly Enantiomerically Enriched Ketone Homoenolate Reagents Prepared by (−)-Sparteine-Mediated γ-Deprotonation of Achiral 1-Alkenyl Carbamates (pages 1423–1427)

      Michael Seppi, Rainer Kalkofen, Jens Reupohl, Roland Fröhlich and Dieter Hoppe

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352966

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      Homoenolate equivalents: Enantiotopos-differentiating deprotonation of achiral 1-alkenyl carbamates with the chiral base n-butyllithium/(−)-sparteine yields configurationally stable lithium homoenolate equivalents. In a subsequent syn or anti substitution (see scheme), γ-substituted O-(1-aryl-1-alkenyl) N,N-diisopropylcarbamates are formed with high enantio- and diastereoselectivity.

    28. Regeneration of Human Tooth Enamel (pages 1428–1431)

      Susanne Busch

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352183

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      Something to get your teeth into: The continuous effect of acids in the mouth leads to dissolution of dental enamel. However, new technology could help to regenerate this unique biomineral. In vitro experiments show that the diffusion of suitable ions through a gelatin layer onto a tooth surface induces the mineralization of fluorapatite layers with a structure similar to tooth enamel (see picture).

    29. Imaging Concentration Profiles of Redox-Active Species with Nanometric Amperometric Probes: Effect of Natural Convection on Transport at Microdisk Electrodes (pages 1431–1435)

      Norman Baltes, Laurent Thouin, Christian Amatore and Jürgen Heinze

      Version of Record online: 2 MAR 2004 | DOI: 10.1002/anie.200352662

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      Nanoprobes for diffusion measurements: Nanometric-sized electrodes (r=80 nm) have been constructed to map concentration profiles within the diffusion layer of a larger microelectrode (r=40 μm) at high resolution (see picture). Comparisons with theoretical predictions demonstrate that, contrary to common wisdom, natural convection in the solution does, to some extent, affect diffusion at microelectrodes.

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