Chemistry - A European Journal

Cover image for Vol. 10 Issue 21

November 5, 2004

Volume 10, Issue 21

Pages 5255–5556

    1. Cover Picture: Towards Organo-Click Chemistry: Development of Organocatalytic Multicomponent Reactions Through Combinations of Aldol, Wittig, Knoevenagel, Michael, Diels–Alder and Huisgen Cycloaddition Reactions (Chem. Eur. J. 21/2004) (page 5255)

      Dhevalapally B. Ramachary and Carlos F. Barbas III

      Version of Record online: 20 OCT 2004 | DOI: 10.1002/chem.200490071

      The cover picture shows a perspective of organo-click chemistry depicting the bringing together of simple reagents, and amino acid and copper/copper sulfate catalysts to produce spirotriones, which are antioxidant compounds. Unlike conventional methods, organo-click chemistry produces stereospecific products with very good yields in a single operation. Multicomponent reactions catalyzed by amino acids and copper sulfate together with simple reagents depicted here support the potential of a rich variety of chemistries available to the prebiotic world and beyond. For more information see the article by D. B. Ramachary and C. F. Barbas III on p. 5323 ff. The picture was designed by Michael Pique at the Scripps Research Institute.

    2. Palladium-Catalyzed Electrophilic Allylation Reactions via Bis(allyl)palladium Complexes and Related Intermediates (pages 5268–5275)

      Kálmán J. Szabó

      Version of Record online: 29 JUL 2004 | DOI: 10.1002/chem.200400261

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      Catalytic allylation of aldehyde, imine, and Michael acceptor substrates can be achieved by using palladium catalysts (see scheme). These transformations proceed through (η1-allyl)palladium complexes, in which the allyl moiety is nucleophilic. This concept paper discusses the rationalization of the nucleophilic reactivity of (η1-allyl)palladium complexes and the synthetic utility of the palladium-catalyzed electrophilic substitution reactions.

    3. Superconductivity in Copper, Silver, and Gold Compounds (pages 5276–5283)

      Sven Larsson

      Version of Record online: 17 AUG 2004 | DOI: 10.1002/chem.200400017

      Superconductor or not—that is the question! AgII and AuII compounds are not superconducting to the same extent as CuII compounds. One reason, according to mixed valence theory, is that the preferred equilibrium geometries of oxidation states I and III tend to be very different from each other, while oxidation state II is high in energy and even unstable.

    4. The Structural Influence in the Stability of Polymer-Bound Diazonium Salts (pages 5285–5296)

      Stefan Bräse, Stefan Dahmen, Crisan Popescu, Maarten Schroen and Franz-Josef Wortmann

      Version of Record online: 23 SEP 2004 | DOI: 10.1002/chem.200400386

      Lifetime predictions: Various new diazonium ions on a polymeric support, with a variety of counterions and complexation with crown ethers, have been prepared. The thermal stability of these resins over a large temperature interval has been investigated. Nonisothermal kinetics applied to DSC data have been used predicting the lifetime of the resins.

    5. Towards Highly Fluorescent and Water-Soluble Perylene Dyes (pages 5297–5310)

      Christopher Kohl, Tanja Weil, Jianqiang Qu and Klaus Müllen

      Version of Record online: 21 SEP 2004 | DOI: 10.1002/chem.200400291

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      Introduction of hydrophilic substituents onto thebayregion of the chromophore (see picture) led to water-soluble perylenetetracarboxylic acid diimide chromophores with high fluorescent quantum yields. Thanks to their high photostability and their absorption and emission maxima above 500 nm, such perylene chromophores are promising candidates for detection in complex biomolecular assemblies, including living cells.

    6. Structure–Property Correlation of a New Family of Organogelators Based on Organic Salts and Their Selective Gelation of Oil from Oil/Water Mixtures (pages 5311–5322)

      Darshak R. Trivedi, Amar Ballabh, Parthasarathi Dastidar and Bishwajit Ganguly

      Version of Record online: 20 SEP 2004 | DOI: 10.1002/chem.200400122

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      Molecular packing and gelling ability of a new class of low-molecular-mass organic gelators derived from simple organic salts have been correlated based on the single-crystal structures of four such gelators and ten non-gelators. The one-dimensional hydrogen-bonded motif for dicyclohexylammonium 4-chlorocinnamate is depicted.

    7. Towards Organo-Click Chemistry: Development of Organocatalytic Multicomponent Reactions Through Combinations of Aldol, Wittig, Knoevenagel, Michael, Diels–Alder and Huisgen Cycloaddition Reactions (pages 5323–5331)

      Dhevalapally B. Ramachary and Carlos F. Barbas III

      Version of Record online: 23 SEP 2004 | DOI: 10.1002/chem.200400597

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      A diversity-oriented synthesis of polysubstituted spirotriones and spirotrione–triazoles were assembled from simple substrates by means of Wittig/Knoevenagel/Diels–Alder, aldol/Knoevenagel/Diels–Alder, and Wittig/Knoevenagel/Diels–Alder/Huisgen cycloaddition reaction sequences in one pot under stereospecific organo/CuI-catalysis (see scheme). These dispirolactones are biologically active antioxidants and radical scavengers.

    8. C[BOND]C Bond Insertion of a Complexed Phosphinidene into 1,6-Methano[10]annulene (pages 5332–5337)

      Rosa E. Bulo, Linda Trion, Andreas W. Ehlers, Fransiscus J. J. de Kanter, Marius Schakel, Martin Lutz, Anthony L. Spek and Koop Lammertsma

      Version of Record online: 23 SEP 2004 | DOI: 10.1002/chem.200400519

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      The first phosphorus-containing 11-membered ring: Reaction of the transient phosphinidene complex [MePW(CO)5] with 1,6-methano[10]annulene results remarkably in the sole formation of the stable C[BOND]C insertion products 1 a (shown here) and 1 b, which have the first phosphorus-containing 11-membered ring. Characterization by X-ray crystallography and NMR spectroscopy was complimented with density functional calculations.

    9. Palladium-Catalyzed Tandem Reaction of Yne–Propargylic Carbonates with Boronic Acids: A Simple Method for the Synthesis of Fused Aromatic Rings through Allene-Mediated Electrocyclization (pages 5338–5344)

      Feng Wang, Xiaofeng Tong, Jiang Cheng and Zhaoguo Zhang

      Version of Record online: 20 SEP 2004 | DOI: 10.1002/chem.200400573

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      Synthesis of fused ring compounds made easy: A series of fused ring compounds was easily prepared directly from palladium-catalyzed coupling reactions of aryl boronic acids and linear yne–propargylic carbonates followed by electrocyclization (see scheme).

    10. Evaluation of the Efficiency of the Photocatalytic One-Electron Oxidation Reaction of Aromatic Compounds Adsorbed on a TiO2 Surface (pages 5345–5353)

      Takashi Tachikawa, Akihiro Yoshida, Sachiko Tojo, Akira Sugimoto, Mamoru Fujitsuka and Tetsuro Majima

      Version of Record online: 23 SEP 2004 | DOI: 10.1002/chem.200400516

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      The crucial interaction between the aromatic compounds and the TiO2 surface is determining the one-electron oxidation efficiency of aromatic compounds adsorbed on the TiO2 surface (see scheme). The reaction does, however, not depend on the oxidation potential of aromatic compounds determined in homogeneous solution.

    11. Diphosphines with Expandable Bite Angles: Highly Active Ethylene Dimerisation Catalysts Based on Upper Rim, Distally Diphosphinated Calix[4]arenes (pages 5354–5360)

      Manuel Lejeune, David Sémeril, Catherine Jeunesse, Dominique Matt, Frédéric Peruch, Pierre J. Lutz and Louis Ricard

      Version of Record online: 8 OCT 2004 | DOI: 10.1002/chem.200400492

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      Turnover frequencies up to 106(mol C2H4) (mol Ni)−1h−1(!): Upon reaction with NiII centres, calix[4]arene-derived diphosphines 1 and 2, two large diphosphines having phosphorus atoms separated by 12 bonds, form chelate complexes in which the ligand bite angle retains considerable flexibility. Activation with methylaluminoxane of the corresponding [NiBr2(diphosphine)] complexes results in highly active ethylene dimerisation catalysts with high turnover frequencies.

    12. Synthesis, Light-Harvesting and Energy-Transfer Properties of Regioregular Silylene-Spaced Alternating [(Donor-SiMe2-)n=1–3-(Acceptor-SiMe2)] Copolymers (pages 5361–5368)

      Yen-Ju Cheng and Tien-Yau Luh

      Version of Record online: 20 SEP 2004 | DOI: 10.1002/chem.200400472

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      A series of silylene-spaced alternating [(donor-SiMe2)n=1–3-(acceptor-SiMe2)] copolymers was synthesized by rhodium-catalyzed hydrosilylation of bisalkynes with bissilyl hydrides (see picture). The polymers exhibit light-harvesting abilities, for which the intensity of the emission is enhanced with larger donor-to-acceptor ratios. No emission originating from the donors was observed in fluorescence spectra, illustrating that intrachain energy transfer is highly efficient along the polymer chain.

    13. Insights into the Reaction of Transplatin with DNA and Proteins: Methionine-Mediated Formation of Histidine–Guanine trans-Pt(NH3)2 Cross-Links (pages 5369–5375)

      Vicente Marchán, Enrique Pedroso and Anna Grandas

      Version of Record online: 23 SEP 2004 | DOI: 10.1002/chem.200400470

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      Exposure of transplatin to a model peptide–oligonucleotide conjugate (see figure) produced histidine–guanine adducts with trans-Pt(NH3)2 cross-links, which displayed different structures and lower stability than those formed with the cis isomer, cisplatin. These findings may reflect the different capacities of these isomers to influence biological processes, such as cisplatin's interference with cell repair mechanisms and its greater cytotoxicity.

    14. Synthesis and Coordinating Ability of an Anionic Cobaltabisdicarbollide Ligand Geometrically Analogous to BINAP (pages 5376–5385)

      Isabel Rojo, Francesc Teixidor, Clara Viñas, Raikko Kivekäs and Reijo Sillanpää

      Version of Record online: 20 SEP 2004 | DOI: 10.1002/chem.200400361

      The two dicarbollide halves in [1,1′-(PPh2)2-3,3′-Co(1,2-C2B9H10)2] swing about one axis in much the same way as the coordinating subunits in BINAP or ferrocenyl phosphine derivatives do. These derivatives and other hinge ligands present different P⋅⋅⋅P distances, thence the potential for different metal surroundings and dispositions. To account for these differences, the general equation Dφ2 = D02 + 4 R2cos2(90−equation image) has been developed.

    15. Asymmetric Desymmetrization Based on an Intramolecular Haloetherification: A Highly Effective and Recyclable Chiral Nonracemic Auxiliary, 2-exo-Methyl-3-endo-phenyl-5-norbornene-2-carboxaldehyde, for meso-1,3- and meso-1,4-Diols (pages 5386–5397)

      Hiromichi Fujioka, Tetsuya Fujita, Naoyuki Kotoku, Yusuke Ohba, Yasushi Nagatomi, Atsushi Hiramatsu and Yasuyuki Kita

      Version of Record online: 23 SEP 2004 | DOI: 10.1002/chem.200400444

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      Discriminating diols: Efficient desymmetrization of meso-1,3- and meso-1,4-diols was achieved by using a 3-endo-phenylnorbornene aldehyde derivative (see scheme).

    16. A Convenient Synthetic Route to Benz[cd]azulenes: Versatile Ligands with the Potential To Bind Metals in an η5, η6, or η7 Fashion (pages 5398–5405)

      Sonya Balduzzi, Helge Müller-Bunz and Michael J. McGlinchey

      Version of Record online: 20 SEP 2004 | DOI: 10.1002/chem.200400425

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      A short and efficient route to stable benz[cd]azulenes, starting from guaiazulene, allows the investigation of their reactivity. Molecule 1, which has been characterised by X-ray crystallography as its chromium tricarbonyl complex (2) undergoes oxidation to 3. Both 1 and 3 react with TCNE giving [4+2] and [2+2] cycloadducts, respectively. The viability of haptotropic migrations of organometallic moieties over the five-, six- and seven-membered rings is discussed.

    17. The Influence of Constitutional Isomerism and Change on Molecular Recognition Processes (pages 5406–5421)

      Avril R. Williams, Brian H. Northrop, Kendall N. Houk, J. Fraser Stoddart and David J. Williams

      Version of Record online: 16 SEP 2004 | DOI: 10.1002/chem.200400221

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      Patience is a virtue when waiting for the bis(1-naphthylmethyl)ammonium ([1 NP/1 NP-H]+) ion, as its hexafluorophosphate salt, to thread its way through the middle of dibenzo[24]crown-8 (DB24C8) in acetonitrile at room temperature. The strict self-assmebly process takes the best part of a month to reach equilibrium! This very same ion complexes more strongly with dipyrido[24]crown-8 (DP24C8) and pyrido[24]crown-8 (P24C8). While strict self-assembly is a thermodynamic phenomenon once equilibrium has been reached in a process, it can often express itself as a kinetic phenomenon at the onset of the process (see scheme).

    18. Ligand Bite Governs Enantioselectivity: Electronic and Steric Control in Pd-Catalyzed Allylic Alkylations by Modular Fenchyl Phosphinites (FENOPs) (pages 5422–5431)

      Bernd Goldfuss, Thomas Löschmann and Frank Rominger

      Version of Record online: 20 SEP 2004 | DOI: 10.1002/chem.200400273

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      Reversibility of enantioselectivity: Fenchyl phosphinites (FENOPs) containing phenyl (1) or 2-anisyl groups (2) yield S enantiomers in allylic alkylations (see scheme), but the enantioselectivity erodes with higher ligand loadings. In contrast, 2-pyridyl (3) groups give R enantiomers in a fashion independent of the loading. Computations on FENOP–Pd transition structures show that the different enantioselectivities originate from “π-face-on” versus “N-edge-on” ligand bites.

    19. CO2 in Supramolecular Chemistry: Preparation of Switchable Supramolecular Polymers (pages 5432–5442)

      Heng Xu and Dmitry M. Rudkevich

      Version of Record online: 23 SEP 2004 | DOI: 10.1002/chem.200306062

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      CO2building block in supramolecular chemistry! Self-assembling polymeric chains and three-dimensional networks can be easily constructed by bubbling CO2 through an apolar solution of calixarene capsules, which contain primary amino groups on the periphery. Multiple carbamate bridges cross-link the structure (see scheme). These insoluble materials can use their capsules to envelop, store, and release guests. They are also two-way switchable. Hydrogen bonds can be broken by using a competitive solvent, or alternatively, CO2 can be thermally released.

    20. Vinyl Sulfoxides as Stereochemical Controllers in Intermolecular Pauson–Khand Reactions: Applications to the Enantioselective Synthesis of Natural Cyclopentanoids (pages 5443–5459)

      Marta Rodríguez Rivero, Inés Alonso and Juan C. Carretero

      Version of Record online: 23 SEP 2004 | DOI: 10.1002/chem.200400443

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      First asymmetric version of an intermolecular Pauson–Khand reaction of unstrained alkenes: o-(N,N-Dimethylamino)phenyl vinyl sulfoxide reacts with a wide variety of terminal alkynes in good yield and in a completely regioselective and highly diastereoselective manner (see scheme). The great synthetic interest of this methodology is illustrated by two very short and efficient enantioselective total syntheses of stereochemically complex natural cyclopentanoids.

    21. Phase-Transfer Agents as Catalysts for a Nucleophilic Substitution Reaction in Microemulsions (pages 5460–5466)

      Maria Häger and Krister Holmberg

      Version of Record online: 20 SEP 2004 | DOI: 10.1002/chem.200306048

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      Mix'n'match! A combined approach, that is, use of a microemulsion as the reaction medium and addition of a phase-transfer agent, gave the highest reaction rate in the substitution reaction shown here.

    22. Aldolase Antibody Activation of Prodrugs of Potent Aldehyde-Containing Cytotoxics for Selective Chemotherapy (pages 5467–5472)

      Subhash C. Sinha, Lian-Sheng Li, Shin-ichi Watanabe, Eiton Kaltgrad, Fujie Tanaka, Christoph Rader, Richard A. Lerner and Carlos F. Barbas III

      Version of Record online: 20 SEP 2004 | DOI: 10.1002/chem.200400419

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      Selective activation of the prodrugs by using antibody 93F3 (see scheme) affords the active iminium drugs via the corresponding aldehyde intermediates. The iminium drugs inhibit the cell proliferation of various cancer cell lines, including Kaposi's sarcoma (SLK) and breast cancer (MDA-MB-435) cell lines.

    23. Crystal and Magnetic Structure of the System Li0.5+0.5xFe2.5−1.5xTixO4 (x=0.16, 0.44, and 0.72) (pages 5473–5480)

      María Angeles Arillo, Gabriel Cuello, María Luisa López, Carlos Pico and María Luisa Veiga

      Version of Record online: 8 OCT 2004 | DOI: 10.1002/chem.200400310

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      Collinear and noncollinear ferromagnetic structures: The magnetic properties of titanium-doped lithium ferrites, Li0.5+0.5xFe2.5−1.5xTixO4, and the main features of their structure are described. The effect of nonmagnetic cations provokes a different behaviour as the titanium content is increased, indicating that the less-substituted phase exhibits a Néel's collinear ferrimagnetic structure (depicted left) that changes to noncollinear (depicted right) in the higher substituted phases.

    24. Synthesis and Self-Assembly of a Rigid Exotopic Bisphenanthroline Macrocycle: Surface Patterning and a Supramolecular Nanobasket (pages 5481–5492)

      Venkateshwarlu Kalsani, Horst Ammon, Frank Jäckel, Jürgen P. Rabe and Michael Schmittel

      Version of Record online: 20 SEP 2004 | DOI: 10.1002/chem.200305770

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      From macrocycles to nanobaskets: The synthesis of a nanoscale macrocycle with exotopic bisphenanthroline sites and its behaviour at the solid/liquid interface (investigated by STM) is described. The HETPHEN approach is explored to envisage heteroleptic assemblies, such as a multicomponent nanobasket. Extensive solution state studies of the nanobasket point to three distinct isomers, models I and II (shown here). The fruitful combination of ESI MS and UV-visible spectroscopy provided additional insight into the mechanistic aspects of this unique multicomponent dynamic assembly.

    25. Regioselective Samarium Diiodide Induced Couplings of Carbonyl Compounds with 1,3-Diphenylallene and Alkoxyallenes: A New Route to 4-Hydroxy-1-enol Ethers (pages 5493–5506)

      Alexandra Hölemann and Hans-Ulrich Reißig

      Version of Record online: 16 SEP 2004 | DOI: 10.1002/chem.200400418

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      SmI2couples again: An efficient method has been developed for the regioselective coupling of samarium ketyls with different allenes (e.g. 1,3-diphenylallene and alkoxyallenes). 4-Hydroxy-1-enol ethers are obtained in the case of methoxyallene (see scheme). In this reaction, methoxyallene serves as an equivalent of acrolein, which cannot be directly used.

    26. Enantioselective Conjugate Addition of Dialkylzinc and Diphenylzinc to Enones Catalyzed by a Chiral Copper(I) Binaphthylthiophosphoramide or Binaphthylselenophosphoramide Ligand System (pages 5507–5516)

      Min Shi, Chun-Jiang Wang and Wen Zhang

      Version of Record online: 27 SEP 2004 | DOI: 10.1002/chem.200400254

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      Excellenteevalues can be achieved in conjugate addition reactions by using the depicted axially chiral binaphthylthiophosphoramide ligand: The ligand can effectively catalyze the asymmetric conjugate addition reaction of dialkylzinc or diphenylzinc to cyclic and acyclic enones to afford the Michael adducts in high yields with excellent ee.

    27. New Organosilyl Derivatives of the Dawson Polyoxometalate [α2-P2W17O61(RSi)2O]6−: Synthesis and Mass Spectrometric Investigation (pages 5517–5523)

      Cédric R Mayer, Catherine Roch-Marchal, Hélène Lavanant, René Thouvenot, Nicole Sellier, Jean-Claude Blais and Francis Sécheresse

      Version of Record online: 28 SEP 2004 | DOI: 10.1002/chem.200400217

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      Three different methods have been applied to synthesize a new organosilyl derivative of the polyoxometalate [α2-P2W17O61(PhSi)2O]6− (left). These hybrids were fully characterized by NMR spectroscopy (29Si, 31P, and 183W) and extensive mass spectrometry (MALDI-TOF and ESI right). The new hybrid polyoxometalates showed unusual redox behavior.

    28. EPR Studies of Amine Radical Cations, Part 1: Thermal and Photoinduced Rearrangements of n-Alkylamine Radical Cations to their Distonic Forms in Low-Temperature Freon Matrices (pages 5524–5534)

      I. Janovský, W. Knolle, S. Naumov and F. Williams

      Version of Record online: 30 SEP 2004 | DOI: 10.1002/chem.200400401

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      The thermal and photochemical transformations of primary amine radical cations have been investigated by using low-temperature EPR spectroscopy. The thermal rearrangement of the n-propylamine radical cation 1.+ to its distonic form 2.+ by a 1,4-hydrogen shift was monitored kinetically as a first-order reaction at 125–140 K (see figure). The results directly verify the intramolecular hydrogen-atom migration, proposed as a key step in the Hofmann–Löffler–Freytag reaction. A surprising result is the formation of relatively stable iminyl radicals RCH[DOUBLE BOND]N. as secondary products.

    29. Benzene-Templated Hydrothermal Synthesis of Metal–Organic Frameworks with Selective Sorption Properties (pages 5535–5540)

      Eun-Young Choi, Kyungsoo Park, Cheol-Min Yang, Hyejin Kim, Jung-Ho Son, Soon W. Lee, Young Hee Lee, Dongwon Min and Young-Uk Kwon

      Version of Record online: 30 SEP 2004 | DOI: 10.1002/chem.200400178

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      Selective sorption: A metal–organic framework (MOF) [Co2(ndc)2(bipyen)]C6H6H2O (2; right) was synthesized by adding benzene into a hydrothermal system that would otherwise yield a different compound, [Co3(ndc)3(bipyen)1.5]H2O (1; left). The benzene guest molecules can be desorbed and the resultant MOF shows selective adsorption properties for benzene and cyclohexene as opposed to other similar ring compounds. H2ndc=2,6-naphthalenedicarboxylic acid, bipyen=trans-1,2-bis(4-pyridyl)ethylene.

    30. Thermal Effects and Vibrational Corrections to Transition Metal NMR Chemical Shifts (pages 5541–5552)

      Sonja Grigoleit and Michael Bühl

      Version of Record online: 30 SEP 2004 | DOI: 10.1002/chem.200400256

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      Beyond static molecules: The effect of zero-point motion and classical thermal averaging on transition metal NMR chemical shifts, as assessed by a perturbational approach and molecular dynamics simulations, respectively (see figure), can be sizeable: These effects can result in a deshielding of individual metal nuclei by several hundreds of ppm with respect to the equilibrium values.

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      Preview: Chem. Eur. J. 21/2004 (page 5556)

      Version of Record online: 20 OCT 2004 | DOI: 10.1002/chem.200490073