Angewandte Chemie International Edition

Cover image for Vol. 42 Issue 35

September 15, 2003

Volume 42, Issue 35

Pages 4109–4267

    1. Cover Picture: Single-Wall Carbon Nanotube–Ferrocene Nanohybrids: Observing Intramolecular Electron Transfer in Functionalized SWNTs (Angew. Chem. Int. Ed. 35/2003) (page 4109)

      Dirk M. Guldi, Massimo Marcaccio, Demis Paolucci, Francesco Paolucci, Nikos Tagmatarchis, Dimitrios Tasis, Ester Vázquez and Maurizio Prato

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200390572

      Carbon Nanotubes are currently a subject of particular interest in materials chemistry. In the Communication by D. M. Guldi, F. Paolucci, M. Prato, and co-workers on page 4206 ff., the preparation of a single-wall nanotube–ferrocene (SWNT–Fc) nanohybrid is described. Photoinduced electron transfer gives rise to a long-lived charge-separated state (SWNT.−–Fc.+); the radical anionic form of the nanotube has been detected by laser flash photolysis.

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      Interactions with Aromatic Rings in Chemical and Biological Recognition (page 4120)

      Emmanuel A. Meyer, Ronald K. Castellano and François Diederich

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200390574

    3. Integrated Microfluidic Systems (pages 4130–4132)

      Rustem F. Ismagilov

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200301660

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      Microchips: Multistep reactions may be catalyzed by enzymes immobilized on microbeads trapped inside microfluidic channels. Large integrated microfluidic circuits can be created by using multilayer soft lithography in poly(dimethylsiloxane). These circuits (see schematic representation) can be used to perform hundreds of different reactions simultaneously, and can be applied to a range of problems, from enzymatic assays to crystallization of proteins.

    4. Conjugated Belts and Nanorings with Radially Oriented p Orbitals (pages 4133–4135)

      Lawrence T. Scott

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200301671

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      Undeterred by the propensity of trigonal carbon atoms to strive for planarity, synthetic chemists have recently succeeded in constructing novel macrocycles with inward-pointing p orbitals (see picture). Individual metal ions are too small to fill the cavity, but fullerenes are just the right size for some of these electron-rich, π-lined hosts.

    5. Solution-Phase Combinatorial Libraries: Modulating Cellular Signaling by Targeting Protein–Protein or Protein–DNA Interactions (pages 4138–4176)

      Dale L. Boger, Joel Desharnais and Kevin Capps

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200300574

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      To bead or not to bead? This is the question posed at the start of the construction of every combinatorial library. The pros and cons of solid-phase and solution-phase library synthesis are discussed along with the authors personal experiences in constructing and using solution-phase libraries (see scheme) to study the modulation of protein–protein and protein–DNA interactions in cellular signal transduction.

    6. Restraining Symmetry in the Formation of Small Polyoxomolybdates: Building Blocks of Unprecedented Topology Resulting From “Shrink-Wrapping” [H2Mo16O52]10−-Type Clusters (pages 4180–4183)

      De-Liang Long, Paul Kögerler, Louis J. Farrugia and Leroy Cronin

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351615

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      A mixed-valence polyoxomolybdate cluster [H2MoVI12MoV4O52]10− was isolated by a new “shrink-wrapping” approach to trap clusters that display low symmetry and nonspherical topology (see scheme; HMTAH=protonated hexamethylenetetraamine). The unprecedented cluster topology results from the restriction of the reorganization of the cluster framework to more symmetrical clusters, yet it reacts with electrophiles, such as FeII.

    7. The Case for Steric Repulsion Causing the Staggered Conformation of Ethane (pages 4183–4188)

      F. Matthias Bickelhaupt and Evert Jan Baerends

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200350947

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      The barrier to rotation in ethane (see picture) is considered a prototypical case of steric hindrance. This view has been recently contradicted, and hyperconjugation has been put forward as the right explanation. The authors argue that there is no reason to abandon the steric repulsion explanation, and discuss why different electronic structure analyses yield different views.

    8. Rebuttal to the Bickelhaupt–Baerends Case for Steric Repulsion Causing the Staggered Conformation of Ethane (pages 4188–4194)

      Frank Weinhold

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351777

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      Two tenets of qualitative MO theory suggest contradictory explanations of ethane torsional barriers, but only one stands up to rigorous examination (see energy level diagrams). Bickelhaupt and Baerends' defense of the neo-steric “four-electron destabilization” concept (right) is shown to be as illusory as its predecessors.

    9. Precision Synthesis of Organic/Inorganic Hybrid Nanocapsules with a Silanol-Functionalized Micelle Template (pages 4194–4197)

      Kyoungmoo Koh, Kohji Ohno, Yoshinobu Tsujii and Takeshi Fukuda

      Article first published online: 25 AUG 2003 | DOI: 10.1002/anie.200351398

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      In a nutshell: An amphiphilic block copolymer that bears protected silanol groups was synthesized by atom-transfer radical polymerization, and the amphiphile was assembled to form a micelle in an aqueous medium. The micelle was mixed with a solution of active silicate, which resulted in the formation of a silica layer on the micelle surface to produce a novel type of organic/inorganic hybrid nanocapsule (see scheme).

    10. Simple and Precise Preparation of a Porous Gel for a Colorimetric Glucose Sensor by a Templating Technique (pages 4197–4200)

      Daisuke Nakayama, Yukikazu Takeoka, Masayoshi Watanabe and Kazunori Kataoka

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351746

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      Red for danger! A glucose-sensitive gel is systematically prepared by careful control of the gel recipe to produce the desired swelling ratio at a given glucose concentration. Subsequently, a periodically ordered porous gel is obtained from the bulk gel by using a closest-packing colloidal crystal as a template; this template is subsequently removed. The gel exhibits expected structural color at certain glucose concentrations and thus can be used as a colorimetric glucose sensor, which may applied as a test for diabetes (see picture).

    11. Template Synthesis of Uniform 1D Mesostructured Silica Materials and Their Arrays in Anodic Alumina Membranes (pages 4201–4203)

      Zhenglong Yang, Zhongwei Niu, Xinyu Cao, Zhenzhong Yang, Yunfeng Lu, Zhibing Hu and Charles C. Han

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200250808

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      Taking control: One-dimensional mesostructured silica materials and their arrays are prepared in anodic alumina membranes. By adjusting the wettability of the alumina pore wall, nanofibers and nanotubes are prepared in a controlled way. The mesostructured silica morphology (see picture) can be adjusted by changing the surfactant concentration. Both the mesopores and the tubular cavities can be incorporated with functional materials, thus forming hierarchical nanocomposites.

    12. Spherical Carbon-Coated Natural Graphite as a Lithium-Ion Battery-Anode Material (pages 4203–4206)

      Masaki Yoshio, Hongyu Wang and Kenji Fukuda

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351203

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      Lithium-ion batteries are the most convenient form of electrical storage. But their natural-graphite anodes are not compatible with propylene carbonate-based electrolytes. The edge planes of the graphite are attacked by the electrolyte, whereas the basal planes remain inert. A technique can be applied to form spherical graphite particles, which maximize the basal-plane exposure while the edge planes remain hidden (see picture). Thus only a small amount of carbon coating is now needed to protect the graphite core from the electrolyte.

    13. Single-Wall Carbon Nanotube–Ferrocene Nanohybrids: Observing Intramolecular Electron Transfer in Functionalized SWNTs (pages 4206–4209)

      Dirk M. Guldi, Massimo Marcaccio, Demis Paolucci, Francesco Paolucci, Nikos Tagmatarchis, Dimitrios Tasis, Ester Vázquez and Maurizio Prato

      Article first published online: 28 JUL 2003 | DOI: 10.1002/anie.200351289

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      A long-lived charge-separated state, SWNT.−–Fc.+, is formed by photoinduced electron transfer in a novel single-wall carbon nanotube–ferrocene (SWNT–Fc) nanohybrid. The presence of SWNT.−, detected by laser flash photolysis, was confirmed by time-resolved pulse radiolysis and steady-state bulk electrolysis.

    14. Reversible Intramolecular Electron Transfer at the Single-Molecule Level (pages 4209–4214)

      Roel Gronheid, Alina Stefan, Mircea Cotlet, Johan Hofkens, Jianqiag Qu, Klaus Müllen, Mark Van der Auweraer, Jan W. Verhoeven and Frans C. De Schryver

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351430

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      Fluctuating electron-transfer rates, both forward and back (see picture), were measured at the single-molecule level for a triphenylamine–perylenediimide donor–acceptor dendrimer. These fluctuations, reminiscent of those seen for forward electron transfer in some large biomolecules and so far not documented for synthetic systems, are induced by the local environment and conformational changes in the dendrimer.

    15. Regioselectivity Control by a Ligand Switch in the Coupling Reaction Involving Allenic/Propargylic Palladium Species (pages 4215–4217)

      Shengming Ma and Guangwei Wang

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351522

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      Tuning the regioselectivity of the Pd-catalyzed coupling reaction of propargylic mesylates and (Z)-2-ethoxycarbonylethenyl zinc iodide or PhZnBr is acheived by subtle choice of the ligand. When PPh3 is the ligand, alkynes are formed, whereas when 2-diphenylphosphanyl-2′-hydroxy-1,1′-binaphthalene is the ligand, allenes are formed.

    16. Superhydrophobicity of Nanostructured Carbon Films in a Wide Range of pH Values (pages 4217–4220)

      Lin Feng, Zhenglong Yang, Jin Zhai, Yanlin Song, Biqian Liu, Yongmei Ma, Zhenzhong Yang, Lei Jiang and Daoben Zhu

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351539

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      Nanostructured graphitelike carbon films are prepared through a simple pyrolysis method. The as-prepared films are superhydrophobic for not only pure water but also corrosive liquids, such as acidic and basic solutions. The picture shows water droplets with pH values of 1.07 (left) and 13.76 (right) in contact with a nanostructured carbon film. This is the first example of superhydrophobicity over the whole range of pH values, without the presence of fluorine-containing compounds.

    17. Amplification of Dynamic Chiral Crown Ether Complexes During Cyclic Acetal Formation (pages 4220–4224)

      Benzion Fuchs, Alshakim Nelson, Alexander Star, J. Fraser Stoddart and Sébastien Vidal

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351558

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      The dynamic duo: A more than tenfold increase in the yield of the chiral macropolycyclic polyether containing two 2,6-disubstituted 1,3,5,7-cis-tetraoxadecalin systems was obtained under thermodynamic conditions from a dynamic combinatorial virtual library with templating cesium ions (>95 % yield, see schematic representation) relative to kinetic syntheses (<8 % yields in their macropolycyclization steps), even when the same template was used.

    18. Total Synthesis of 1-O-Methyllateriflorone (pages 4225–4229)

      K. C. Nicolaou, Pradip K. Sasmal, Hao Xu, Kenji Namoto and Andreas Ritzén

      Article first published online: 25 AUG 2003 | DOI: 10.1002/anie.200351805

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      The unique spiroxalactone framework of lateriflorone (1) consists of a prenylated dihydrobenzoquinone moiety and a trioxatetracyclotetradecane system. A tandem Claisen rearrangement/Diels–Alder cascade was the key step in the synthesis of the complex tetradecane system, which was then used to prepare 1-O-methyllateriflorone (2).

    19. Diastereoselective Radical-Mediated Hydrogen-Atom Abstraction (pages 4230–4233)

      Philippe Renaud, Florent Beaufils, Laurence Feray and Kurt Schenk

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351829

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      A tin-free radical tandem reaction leads to optically active α-methylenelactones (e.g. 1). The initial radical-mediated hydrogen-atom abstraction from a chiral acetal is highly stereoselective (see scheme). The stereochemical outcome of such reactions is governed by rules similar to those developed for related cyclization processes.

    20. Organocatalytic Asymmetric Domino Knoevenagel/Diels–Alder Reactions: A Bioorganic Approach to the Diastereospecific and Enantioselective Construction of Highly Substituted Spiro[5,5]undecane-1,5,9-triones (pages 4233–4237)

      D. B. Ramachary, Naidu S. Chowdari and Carlos F. Barbas III

      Article first published online: 25 AUG 2003 | DOI: 10.1002/anie.200351916

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      A practical and environmentally friendly organocatalytic process for the synthesis of optically active highly substituted spiro[5,5]undecane-1,5,9-triones was achieved through the reaction of an aldehyde, an enone, and Meldrum's acid in the presence of a catalytic amount of chiral amino acid (see scheme). The Diels–Alder products were obtained as single diastereomers in excellent yields and enantiomeric excesses.

    21. Total Synthesis of an Atropdiastereomer of RP-66453 and Determination of Its Absolute Configuration (pages 4238–4241)

      Michèle Bois-Choussy, Pierre Cristau and Jieping Zhu

      Article first published online: 25 AUG 2003 | DOI: 10.1002/anie.200351996

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      The absolute configuration (aR, S, S, S, S, S) was assigned to the natural product RP-66453 (1) after the total synthesis of its atropdiastereomer and spectroscopic studies on the two compounds. A sequence of SNAr-based cycloetherification and an intramolecular atropdiastereoselective Suzuki–Miyaura coupling were used for the construction of the elusive A-B-O-C bicyclic skeleton of RP-66453.

    22. Highly Diastereoselective Oxy-Michael Additions of Enantiopure δ-Lactol Anions to Nitroalkenes: Asymmetric Synthesis of 1,2-Amino Alcohols (pages 4241–4244)

      Nicola J. Adderley, David J. Buchanan, Darren J. Dixon and Dramane I. Lainé

      Article first published online: 25 AUG 2003 | DOI: 10.1002/anie.200352007

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      The “naked” alkoxide 1 of (S)-6-methyl-δ-lactol acts as an excellent chiral hydroxide equivalent in highly diastereoselective oxy-Michael additions to nitroalkenes (see scheme). The excellent stereoinduction arises from what becomes a superb protecting group in the resulting 1,2-amino alcohol products. R1=alkyl, aryl, furanyl, thiophenyl; R2,R3=[BOND](CH2)3CHCH3O[BOND].

    23. Three-Component Enantioselective Synthesis of Propargylamines through Zr-Catalyzed Additions of Alkyl Zinc Reagents to Alkynylimines (pages 4244–4247)

      Laura C. Akullian, Marc L. Snapper and Amir H. Hoveyda

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200352081

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      Readily available amino acid based chiral ligands are used in a three-component Zr-catalyzed enantioselective synthesis of propargylamines (see schemes). The reaction affords important enantiomerically enriched building blocks that are not conveniently accessible by alternative catalytic methods.

    24. A Facile and Rapid Route to Highly Enantiopure 1,2-Diols by Novel Catalytic Asymmetric α-Aminoxylation of Aldehydes (pages 4247–4250)

      Guofu Zhong

      Article first published online: 25 AUG 2003 | DOI: 10.1002/anie.200352097

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      R- orS-configured 1,2-diol precursors are formed in good yields (54–86 %) and with excellent enantioselectivities (94 to 99 % ee) by using a simple one-pot sequence—catalytic α-aminoxylation of aldehydes followed by in situ reduction with NaBH4—with L- or D-proline as the catalyst and nitrosobenzene as the oxygen source (see scheme).

    25. Amorphous Metal Fluorides with Extraordinary High Surface Areas (pages 4251–4254)

      Erhard Kemnitz, Udo Groß, Stephan Rüdiger and Chandra S. Shekar

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351278

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      Super acidic solids: A new two-step route to high-surface-area metal fluorides is reported, by which amorphous AlF3 can be prepared having a BET(N2) surface area of more than 200 m2 g−1 (see SEM image). This HS-AlF3 shows a very high Lewis acidity and consequently a high catalytic activity.

    26. Catalyst-Controlled Stereoselective Combinatorial Synthesis (pages 4254–4257)

      Lutz F. Tietze, Nils Rackelmann and Govindasamy Sekar

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351129

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      Stereochemical diversity as a novel concept in combinatorial chemistry for the synthesis of nonpeptidic biologically active compounds is introduced. As an example, the combination of the hydrogenation of imines in the presence of either enantiomer of a chiral Ru catalyst with a domino reaction led to the targeted construction of 12 of the 16 possible stereoisomers of emetine (1).

    27. Palladium-Catalyzed Synthesis of 2-Aminoindoles by a Heteroanulation Reaction (pages 4257–4260)

      Bernhard Witulski, Carole Alayrac and Lali Tevzadze-Saeftel

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351977

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      Chelates are the key: A conceptually novel indole ring forming reaction through heteroanulation is available through the palladium-catalyzed reaction of N-alkenylanilides with primary or secondary amines. The key feature is the formation of an unprecedented σ,π-chelated palladium species (see scheme); nitrogen nucleophiles can add to the activated alkyne unit of this species to form the indole skeleton. (X=I, Br; HNR2R3=prim. or sec. amine; Ts=tosyl.)

    28. Highly Branched Oligosaccharides: A General Strategy for the Synthesis of Multiantennary N-Glycans with a Bisected Motif (pages 4261–4263)

      Harald Weiss and Carlo Unverzagt

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200351625

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      Squeezing in a sugar: A modular building-block approach was the strategy used in a clever general synthesis of the sterically crowded triantennary N-glycans bearing an additional bisecting GlcNAc motif (see formula). Key steps include the use of the small trifluoroacetyl protective group and the late introduction of the α1,6-arm.

    29. Preview: Angew. Chem. Int. Ed. 35/2003 (page 4267)

      Article first published online: 15 SEP 2003 | DOI: 10.1002/anie.200390576

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