Chemistry - A European Journal

Cover image for Vol. 12 Issue 16

May 24, 2006

Volume 12, Issue 16

Pages 4207–4463

    1. Cover Picture: Ligand-Template Directed Assembly: An Efficient Approach for the Supramolecular Encapsulation of Transition-Metal Catalysts (Chem. Eur. J. 16/2006) (page 4207)

      Arjan W. Kleij and Joost N. H. Reek

      Version of Record online: 17 MAY 2006 | DOI: 10.1002/chem.200690048

      Encapsulated catalysts are discussed in the Concept article by J. N. H. Reek and A. W. Kleij on p. 4218 ff. The authors show how template ligands can be used to form assemblies in which transition-metal catalysts are encapsulated. These novel supramolecular catalysts are not only aesthetically attractive but show improved activity and selectivities compared with their non-encapsulated analogues.

    2. Ligand-Template Directed Assembly: An Efficient Approach for the Supramolecular Encapsulation of Transition-Metal Catalysts (pages 4218–4227)

      Arjan W. Kleij and Joost N. H. Reek

      Version of Record online: 22 FEB 2006 | DOI: 10.1002/chem.200500875

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      Molecular encapsulation of transition-metal catalysts (see figure, for example) by template ligands is described. The catalysts obtained show unusual reactivity and selectivity behaviour which will also be discussed in detail.

    3. To the Core of Autocatalysis in Cyclohexane Autoxidation (pages 4229–4240)

      Ive Hermans, Pierre A. Jacobs and Jozef Peeters

      Version of Record online: 18 APR 2006 | DOI: 10.1002/chem.200600189

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      The .OH radical breaking away from dissociating cyclohexyl hydroperoxide can abstract an αH atom from cyclohexanone in a concerted, low-barrier reaction. Compared with homolytic dissociation, the stabilized ketonyl and cyclohexoxy radical, hydrogen-bonded to H2O, are forced apart by the energy drop after the transition state, thus contributing to the high initiation efficiency of this newly discovered reaction (see scheme).

    4. Fullerene Polypyridine Ligands: Synthesis, Ruthenium Complexes, and Electrochemical and Photophysical Properties (pages 4241–4248)

      Zhiguo Zhou, Ginka H. Sarova, Sheng Zhang, Zhongping Ou, Fatma T. Tat, Karl M. Kadish, Luis Echegoyen, Dirk M. Guldi, David I. Schuster and Stephen R. Wilson

      Version of Record online: 31 MAR 2006 | DOI: 10.1002/chem.200600021

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      Coupled together: A series of fullerene–polypyridine ligands (shown here) were designed to have direct electronic couplings between the fullerene core and the pyridyl nitrogen atoms. Their coordination complexes with ruthenium(II) formed linear rodlike donor–acceptor systems with interesting electrochemical and photophysical properties.

    5. Site-Selective Formation of Optically Active Inclusion Complexes of Alkoxo-Subphthalocyanines with β-Cyclodextrin at the Toluene/Water Interface (pages 4249–4260)

      Kenta Adachi and Hitoshi Watarai

      Version of Record online: 31 MAR 2006 | DOI: 10.1002/chem.200501330

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      Solvent-dependent facial reactions: β-CD⋅RO-Subpc inclusion complexes were shown to exhibit site-selective inclusion complex formation (see scheme) at the liquid/liquid interface. β-CD adsorbed at the interface formed the inclusion complex with its primary face, whereas, in DMSO, the secondary face of β-CD bound favorably to RO-Subpc.

    6. Tuning the Thermotropic and Lyotropic Properties of Liquid-Crystalline Terpyridine Ligands (pages 4261–4274)

      Franck Camerel, Bertrand Donnio, Cyril Bourgogne, Marc Schmutz, Daniel Guillon, Patrick Davidson and Raymond Ziessel

      Version of Record online: 31 MAR 2006 | DOI: 10.1002/chem.200501431

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      The nature of the linker has an influence on the thermotropic and lytotropic properties of terpyridine-based mesogenic ligands. Variation of the substituents leads to different mesophase structures (columns and lamella, see scheme).

    7. Photochromic Reactions of Diarylethenes in Single Crystals with Intermolecular O[BOND]H⋅⋅⋅N Hydrogen-Bonding Networks (pages 4275–4282)

      Masakazu Morimoto and Masahiro Irie

      Version of Record online: 31 MAR 2006 | DOI: 10.1002/chem.200501148

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      A photochromic diarylethene possessing carboxyl groups formed various types of supramolecular architectures through hydrogen-bonding interactions in both the homocrystal and in the cocrystals with bipyridine derivatives (4,4′-, 2,4′-, and 2,2′-bipyridines). The linear-chain structure obtained in the 4,4′-bipyridine cocrystal is shown here. Absorption spectra of the colored crystals varied depending on the conformation of the diarylethene molecules packed inside the crystals.

    8. pKa Switching Induced by the Change in the π-Conjugated System Based on Photochromism (pages 4283–4288)

      Yuka Odo, Kenji Matsuda and Masahiro Irie

      Version of Record online: 4 APR 2006 | DOI: 10.1002/chem.200501292

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      Making the switch: Diarylethene derivatives containing a 2,5-diaryl-3-thienyl group showed reversible, photoinduced changes in pKa based on photoisomerization between the open- and closed-ring isomers (see scheme). The pKa changed as a result of the change in the π-conjugated system.

    9. Solvent Exchange in Thermally Stable Resorcinarene Nanotubes (pages 4289–4296)

      Heidi Mansikkamäki, Sara Busi, Maija Nissinen, Antti Åhman and Kari Rissanen

      Version of Record online: 28 MAR 2006 | DOI: 10.1002/chem.200501201

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      Resorcinarene crystals with tubular pores (see picture) are formed with the aid of solvent templation. The small solvent molecules can be removed from the tube interiors and then the tubes can be filled with other solvents.

    10. Interaction Energies for the Purine Inhibitor Roscovitine with Cyclin-Dependent Kinase 2: Correlated Ab Initio Quantum-Chemical, DFT and Empirical Calculations (pages 4297–4304)

      Petr Dobeš, Michal Otyepka, Miroslav Strnad and Pavel Hobza

      Version of Record online: 31 MAR 2006 | DOI: 10.1002/chem.200501269

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      The total stabilisation energy between roscovitine and cyclin-dependent kinase 2 (shown here) is very large (66 kcal mol−1) and originates predominantly from dispersion energy. A few amino acid residues contribute significantly to the binding of roscovitine and cdk2, whereas many amino acids make a negligible contribution.

    11. Micellization and Reversible pH-Sensitive Phase Transfer of the Hyperbranched Multiarm PEI–PBLG Copolymer (pages 4305–4312)

      Huayu Tian, Xuesi Chen, Hao Lin, Chao Deng, Peibiao Zhang, Yen Wei and Xiabin Jing

      Version of Record online: 28 MAR 2006 | DOI: 10.1002/chem.200501322

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      Different micelle systems in different media: The amphiphilic hyperbranched multiarm PEI–PBLG copolymer can form unimolecular micelles (see figure) in solvents in which it is highly soluble and exhibits reversible pH-sensitive phase-transfer behavior. PEI–PBLG can also form multimolecular core-shell micelles in aqueous solution with positive charges on the micellar surface.

    12. Ligand Cleavage Put into Reverse: P[BOND]C Bond Breaking and Remaking in an Alkylphosphane Iron Complex (pages 4313–4320)

      Stephan W. Kohl, Frank W. Heinemann, Markus Hummert, Walter Bauer and Andreas Grohmann

      Version of Record online: 10 MAR 2006 | DOI: 10.1002/chem.200501577

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      CO will fix it: Complexation of the pyridine-derived tetrapodal tetraphosphane ligand 2,6-C5H3N[CMe(CH2PMe2)2]2 (1) and FeX2⋅6 H2O (2) in methanol proceeds with breaking of one Me2P[BOND]CH2CMeR bond to give different iron(II) complexes 3 and 4, depending on the reaction temperature and the nature of the counterion X. The broken P[BOND]C bond is repaired and 1 is regenerated upon reaction of the tetrafluoroborate analogue of 4 with CO.

    13. Enantio- and Diastereoselective Michael Addition Reactions of Unmodified Aldehydes and Ketones with Nitroolefins Catalyzed by a Pyrrolidine Sulfonamide (pages 4321–4332)

      Jian Wang, Hao Li, Bihshow Lou, Liansuo Zu, Hua Guo and Wei Wang

      Version of Record online: 31 MAR 2006 | DOI: 10.1002/chem.200600115

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      Organocatalysis: (S)-Pyrrolidine sulfonamide 1 has been shown to promote highly enantio- and/or diastereoselective Michael addition of aldehydes and ketones to nitroolefins. The mechanistic studies have been conducted to understand the origin of its high catalytic activities.

    14. Bidentate Phosphorus Baskets by Intramolecular Phosphinidene Addition (pages 4333–4340)

      Sander G. A. van Assema, Andreas W. Ehlers, Frans J. J. de Kanter, Marius Schakel, Anthony L. Spek, Martin Lutz and Koop Lammertsma

      Version of Record online: 10 MAR 2006 | DOI: 10.1002/chem.200501531

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      A basket case: Rigid bidentate phosphorus baskets are accessible by intramolecular phosphinidene addition to the C[DOUBLE BOND]C bond of Mo-complexed, seven-membered phosphorus heterocycles in which the phosphorus atom is flanked by CH2, NCH3, or O groups (see picture).

    15. Rapid and Effective Adsorption of Lead Ions on Fine Poly(phenylenediamine) Microparticles (pages 4341–4350)

      Mei-Rong Huang, Qian-Yun Peng and Xin-Gui Li

      Version of Record online: 23 MAR 2006 | DOI: 10.1002/chem.200501070

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      Taking the lead: The adsorption data of Pb2+ ions onto poly(phenylenediamine) microparticles fit the Langmuir isotherm and follow pseudo-second-order kinetics. The maximum Pb2+ ion adsorbance and adsorptivity are 253 mg g−1 and 99.8 %, respectively (see picture). The adsorption is very rapid with a loading half-time of 2 min and an adsorption rate of 95 mg g−1 min−1. A complexation mechanism between Pb2+ ions and [DOUBLE BOND]N[BOND] groups has been proposed.

    16. π-Conjugated Chelating Polymers with Charged Iridium Complexes in the Backbones: Synthesis, Characterization, Energy Transfer, and Electrochemical Properties (pages 4351–4361)

      Shu-Juan Liu, Qiang Zhao, Run-Feng Chen, Yun Deng, Qu-Li Fan, Fu-You Li, Lian-Hui Wang, Chun-Hui Huang and Wei Huang

      Version of Record online: 20 MAR 2006 | DOI: 10.1002/chem.200501095

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      Red-light materials: Efficient energy transfer from host to guest was detected in attractive π-conjugated chelating polymers in which fluorene segments were used as hosts and charged iridium complexes as guests (see picture). This kind of polymer is expected to be useful as a new red-light emitting material.

    17. Synthesis of Small Tripeptide Molecules through a Catalysis Sequence Comprising Metathesis and Aminohydroxylation (pages 4362–4371)

      Jan Streuff, Martin Nieger and Kilian Muñiz

      Version of Record online: 23 MAR 2006 | DOI: 10.1002/chem.200501123

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      Two steps with homogeneous catalysts convert simple amino acids into pseudopeptides. The overall sequence employs N-acroyl amino esters and metathesis for synthesis of fumaric amides. These are further converted by aminohydroxylation into tripeptidic structures with a central hydroxy aspartaric acid moiety. The approach is highly diverse; for example, a mixture of only two different substrates produces up to eight different tripeptides (see scheme).

    18. Addition of Carbenes to the Sidewalls of Single-Walled Carbon Nanotubes (pages 4372–4379)

      Holger F. Bettinger

      Version of Record online: 23 MAR 2006 | DOI: 10.1002/chem.200501217

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      Unexpected intermediate: The addition of singlet dichlorocarbene to a single-walled carbon nanotube occurs stepwise with a diradicaloid intermediate according to density functional computations. The picture shows the structure of the intermediate calculated for addition of CCl2 to a finite model of a (5,5) armchair nanotube. Reactions of CH2 with armchair and zigzag nanotubes are also discussed.

    19. Practical Highly Enantioselective Synthesis of Propargylamines through a Copper-Catalyzed One-Pot Three-Component Condensation Reaction (pages 4380–4392)

      Nina Gommermann and Paul Knochel

      Version of Record online: 24 MAR 2006 | DOI: 10.1002/chem.200501233

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      Enantioselective propargylamine synthesis: The copper(I)/quinap-catalyzed three-component reaction of alkynes, aldehydes, and secondary amines leading to enantiomerically enriched functionalized protected propargylamines under mild reaction conditions is investigated (see scheme).

    20. Structure and Total Synthesis of Aspernigerin: A Novel Cytotoxic Endophyte Metabolite (pages 4393–4396)

      Li Shen, Yong-Hao Ye, Xiao-Ting Wang, Hai-Liang Zhu, Chen Xu, Yong-Cun Song, Hai Li and Ren-Xiang Tan

      Version of Record online: 23 MAR 2006 | DOI: 10.1002/chem.200501423

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      Antitumor agents: Aspernigerin, a novel cytotoxic alkaloid consisting of an unprecedented structural framework (see figure) has been isolated and shown to exhibit cytotoxic activity greater than that of 5-fluorouracil. A feasible total synthetic route for aspernigerin has been established for further pharmacological research.

    21. New Macrocycles with Planar Chirality—Synthesis and Determination of Absolute Configurations (pages 4397–4406)

      Jarosław Kalisiak, Paweł Skowronek, Jacek Gawroński and Janusz Jurczak

      Version of Record online: 24 MAR 2006 | DOI: 10.1002/chem.200501409

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      A perfect match: The synthesis of diazacoronands with planar chirality and their structures are presented. Absolute configurations were determined independently by theoretical methods (example shown right) and by X-ray structure analysis (example shown left), and these gave comparable results.

    22. Microwave-Assisted Suzuki Coupling Reactions with an Encapsulated Palladium Catalyst for Batch and Continuous-Flow Transformations (pages 4407–4416)

      Ian R. Baxendale, Charlotte M. Griffiths-Jones, Steven V. Ley and Geoffrey K. Tranmer

      Version of Record online: 4 APR 2006 | DOI: 10.1002/chem.200501400

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      Just pop it in the microwave: Efficient microwave-assisted Suzuki coupling reactions can be performed in a continuous flow fashion using an encapsulated Pd catalyst (see scheme).

    23. The Mechanism of the Hydroalkoxycarbonylation of Ethene and Alkene–CO Copolymerization Catalyzed by PdII–Diphosphine Cations (pages 4417–4430)

      Jianke Liu, Brian T. Heaton, Jonathan A. Iggo, Robin Whyman, Jamie F. Bickley and Alexander Steiner

      Version of Record online: 24 MAR 2006 | DOI: 10.1002/chem.200501398

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      The intermediates in the “hydride” and “carbomethoxy” cycles for ethene hydromethoxycarbonylation and CO–ethene copolymerization were characterized by using NMR spectroscopy. Alkene insertion into the Pd[BOND]carboalkoxy bond occurs readily (see scheme), inconsistent with the current consensus that slow olefin insertion into this bond is responsible for the dominance of the hydride pathway in hydrocarboxylation.

    24. trans-1-Sulfonylamino-2-isoborneolsulfonylaminocyclohexane Derivatives: Excellent Chiral Ligands for the Catalytic Enantioselective Addition of Organozinc Reagents to Ketones (pages 4431–4445)

      Vicente J. Forrat, Oscar Prieto, Diego J. Ramón and Miguel Yus

      Version of Record online: 31 MAR 2006 | DOI: 10.1002/chem.200501397

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      Ligand design: The catalytic enantioselective synthesis of tertiary alcohols is a major challenge in synthetic organic chemistry. The reaction between poor electrophilic ketones and organozinc reagents catalyzed by ligands derived from isoborneolsulfonamides (see scheme) is presented as a possible answer to this challenge.

    25. Design and Synthesis of Novel Propellanes by Using Claisen Rearrangement and Ring-Closing Metathesis as the Key Steps (pages 4446–4450)

      Sambasivarao Kotha and Mirtunjay Kumar Dipak

      Version of Record online: 28 MAR 2006 | DOI: 10.1002/chem.200501366

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      Caged compounds: Hexacyclic caged compounds are prepared by a combination of Claisen rearrangement and ring-closing metathesis (RCM, see scheme). This methodology opens up a new route to novel caged compounds of higher order ring systems.

    26. The Intermediate Frequency Modes of Single- and Double-Walled Carbon Nanotubes: A Raman Spectroscopic and In Situ Raman Spectroelectrochemical Study (pages 4451–4457)

      Martin Kalbac, Ladislav Kavan, Markéta Zukalová and Lothar Dunsch

      Version of Record online: 22 MAR 2006 | DOI: 10.1002/chem.200501364

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      The intermediate frequency modes (IFM) of single- and double-walled carbon nanotubes were analyzed by Raman spectroscopy and in situ Raman spectroelectrochemistry. The spectra showed evidence that the IFM are diameter dependent. This allowed clear identification of intrinsic features of carbon nanotubes in the IFM region. The figure shows the Raman spectrum of a double-walled carbon nanotube excited by 2.18 eV, and the magnified IFM region.

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      Preview: Chem. Eur. J. 16/2006 (page 4463)

      Version of Record online: 17 MAY 2006 | DOI: 10.1002/chem.200690050