Chemistry - A European Journal

Cover image for Vol. 13 Issue 34

November 26, 2007

Volume 13, Issue 34

Pages 9415–9719

  1. Cover Picture

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    1. Cover Picture: Synthesis and Properties of TRANSDIP, a Rigid Chelator Built upon a Cyclodextrin Cavity: Is TRANSDIP an Authentic trans-Spanning Ligand? (Chem. Eur. J. 34/2007) (page 9415)

      Laurent Poorters, Dominique Armspach, Dominique Matt, Loïc Toupet, Sylvie Choua and Philippe Turek

      Version of Record online: 16 NOV 2007 | DOI: 10.1002/chem.200790130

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      Spanning over 50 years of research… Venanzi, Van Leeuwen, Protasiewicz, Gelman, and others have been involved in the design and synthesis of so-called trans-spanning diphosphines (see examples depicted). Chelating ligands of this type have become very useful in homogeneous catalysis. In fact, most of these ligands do not always behave as they are supposed to, namely as trans-binders, their reactions with transition metals frequently leading to cis-complexes and sometimes also to non-chelating structures. In their Full Paper on page 9448 ff., D. Matt, D. Armspach and co-workers describe the ligand TRANSDIP, a cyclodextrin-derived, rigidified diphosphine, which provides trans-chelated complexes exclusively when treated with d8-metal halides. A complex of this type is illustrated on the bottom right of the picture, which also shows the Strasbourg skyline.

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  3. News

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  4. Concept

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    1. The Progression of Synthetic Strategies to Assemble Titanium Complexes Bearing the Terminal Imide Group (pages 9428–9440)

      Alison R. Fout, Uriah J. Kilgore and Daniel J. Mindiola

      Version of Record online: 28 SEP 2007 | DOI: 10.1002/chem.200701064

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      When you think titanium, think imide! The synthesis of terminal titanium imides is described in this account. The incorporation of this functional group has evolved from the more generic approach to more complex or unusual methods. Past and current synthetic strategies to incorporate the terminal imide functionality are explained with particular emphasis on low-coordinate titanium environments bearing this ubiquitous but vital type of motif.

  5. Full Papers

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    1. Breaking Symmetry: Spontaneous Resolution of a Polyoxometalate (pages 9442–9447)

      Yu Hou, Xikui Fang and Craig L. Hill

      Version of Record online: 23 OCT 2007 | DOI: 10.1002/chem.200701160

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      Spontaneous chemistry: A chiral cluster compound, [Hf(PW11O39)2]10− has been obtained by spontaneous resolution (see figure) upon crystallization in the absence of any chiral source. Optically active crystals of both enantiomers were isolable and spectroscopically distinguishable.

    2. Synthesis and Properties of TRANSDIP, a Rigid Chelator Built upon a Cyclodextrin Cavity: Is TRANSDIP an Authentic trans-Spanning Ligand? (pages 9448–9461)

      Laurent Poorters, Dominique Armspach, Dominique Matt, Loïc Toupet, Sylvie Choua and Philippe Turek

      Version of Record online: 17 OCT 2007 | DOI: 10.1002/chem.200700831

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      Tailor-made fortranschelation: A remarkably rigid diphosphane has been obtained by capping the entrance of a cyclodextrin with two “PPh” units. When treated with Group 10 metal halides, this ligand not only behaves exclusively as a chelating ligand, but also selectively forms trans complexes (see picture).

    3. 1,x-Elimination Reactions: Extending the Limits of a Classical Organic Reaction (pages 9462–9477)

      Christian Werner, Henning Hopf, Ina Dix, Peter Bubenitschek and Peter G. Jones

      Version of Record online: 26 OCT 2007 | DOI: 10.1002/chem.200700827

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      Stretching your imagination: A classical 1,2-elimination reaction can be significantly “extended” or “stretched” by introducing unsaturated spacer elements between the two carbon atoms carrying the two substituents to be eliminated. Typical unsaturated spacers are double and triple bonds, aromatic and heteroaromatic rings. The reactive intermediates generated in these 1,x-eliminations cyclodimerize in a secondary step to yield novel cyclic polyacetylenes or cyclophanes.

    4. Peri- and Enantioselectivity of Thermal, Scandium-, and [Pybox/Scandium]-Catalyzed Diels–Alder and Hetero-Diels–Alder Reactions of Methyl (E)-2-Oxo-4-aryl-butenoates with Cyclopentadiene (pages 9478–9485)

      Giovanni Desimoni, Giuseppe Faita, Marco Toscanini and Massimo Boiocchi

      Version of Record online: 14 SEP 2007 | DOI: 10.1002/chem.200700995

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      What goes around comes around: The reaction of cyclopentadiene with methyl(E)-oxo-4-aryl-3-butenoates 2 is catalyzed by the scandium(III) triflate complex of pyridinebis(oxazoline) 1. The Diels–Alder (DA) and hetero-Diels–Alder (HDA) reactions are in competition, and their products (2R,3R)-3 and (4R,4aS,7aR)-5 are obtained with up to >99 % ee (see scheme; OTf=triflate). The interconversions of 5[RIGHTWARDS ARROW]3 and 3[RIGHTWARDS ARROW]5 are achieved by the thermal Claisen and [3,3]-sigmatropic rearrangements, respectively.

    5. Synthesis of Highly Modified DNA by a Combination of PCR with Alkyne-Bearing Triphosphates and Click Chemistry (pages 9486–9494)

      Johannes Gierlich, Katrin Gutsmiedl, Philipp M. E. Gramlich, Alexandra Schmidt, Glenn A. Burley and Thomas Carell

      Version of Record online: 17 SEP 2007 | DOI: 10.1002/chem.200700502

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      Clicking by the hundred: Alkyne-bearing triphosphates were efficiently incorporated into long DNA strands by using PCR. Subsequent copper(I)-catalyzed cycloaddition of these alkynes with azides (“click chemistry”) resulted in modified DNA strands decorated with sugar moieties (see scheme). The reaction proceeded with almost quantitative conversion, even with DNA strands containing almost 900 alkynes.

    6. Vesicles of a New Salt-Free Cat-anionic Fluoro/Hydrocarbon Surfactant System (pages 9495–9502)

      Xin Li, Shuli Dong, Xiangfeng Jia, Aixin Song and Jingcheng Hao

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/chem.200700778

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      Layer upon layer of skins: Vesicles of a new salt-free cat-anionic fluoro/hydrocarbon surfactant system have been prepared and analyzed by freeze-fracture and cryo-transmission electron microscopy. The formation of vesicles (see figure) shows that the electrostatic interaction between the cationic C14DMAOH+ and anionic C7F15CF[DOUBLE BOND]CHCOO is larger than the nonsynergistic interaction between the stiff fluorocarbon chains and the soft hydrocarbon chains of the surfactants.

    7. Location of the Hole and Acid Proton in Neutral Nonprotonated and Protonated Mixed (Phthalocyaninato)(porphyrinato) Yttrium Double-Decker Complexes: Density Functional Theory Calculations (pages 9503–9514)

      Yuexing Zhang, Xue Cai, Ping Yao, Hui Xu, Yongzhong Bian and Jianzhuang Jiang

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/chem.200700132

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      Locating holes and protons: The structure and properties of the neutral, reduced, and protonated forms of a mixed (phthalocyaninato)(porphyrinato) yttrium complex, [(Pc)Y(Por)], have been studied by DFT calculations. It has been revealed that the acid proton prefers to localize on the Por ring rather than on the Pc ring despite the localization of the hole on the Pc ring in [(Pc)Y(Por)] (see scheme).

    8. A Polyoxyethylene-Substituted Bimetallic Europium Helicate for Luminescent Staining of Living Cells (pages 9515–9526)

      Anne-Sophie Chauvin, Steve Comby, Bo Song, Caroline D. B. Vandevyver, Frédéric Thomas and Jean-Claude G. Bünzli

      Version of Record online: 18 SEP 2007 | DOI: 10.1002/chem.200700883

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      A hexadentate ditopic ligand fitted with polyoxyethylene substituent has been synthesized, which self-assembles in water with LnIII ions to yield stable triple-stranded bimetallic helicates. A proof of principle is given for the use of the non-cytotoxic EuIII edifice as luminescent probe for the staining of HeLa cells (see figure).

    9. Ferrocenylethynyl Derivatives of Nucleoside Triphosphates: Synthesis, Incorporation, Electrochemistry, and Bioanalytical Applications (pages 9527–9533)

      Petra Brázdilová, Milan Vrábel, Radek Pohl, Hana Pivoňková, Luděk Havran, Michal Hocek and Miroslav Fojta

      Version of Record online: 25 SEP 2007 | DOI: 10.1002/chem.200701249

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      Ferrocene-labeled nucleoside triphosphates were prepared by cross-coupling reactions and incorporated into oligonucleotides by primer extension. Electrochemical analysis shows significant analytically applicable differences in redox potentials of ferrocene bound to dNTPs or to DNA (see picture).

    10. Design, Synthesis, and Biological Properties of Highly Potent Tubulysin D Analogues (pages 9534–9541)

      Andrew W. Patterson, Hillary M. Peltier, Florenz Sasse and Jonathan A. Ellman

      Version of Record online: 7 SEP 2007 | DOI: 10.1002/chem.200701057

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      The essential structural features for the potent cytotoxicity of tubulysin D have been established for the first time by the synthesis and evaluation of a series of analogues (see figure). By identifying functionality that surprisingly is not necessary for activity, highly potent cell-growth inhibitors have been developed that are smaller and considerably more stable than tubulysin D.

    11. Disulfides, Imines, and Metal Coordination within a Single System: Interplay between Three Dynamic Equilibria (pages 9542–9546)

      Rupam J. Sarma, Sijbren Otto and Jonathan R. Nitschke

      Version of Record online: 18 SEP 2007 | DOI: 10.1002/chem.200701228

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      Working within the system: We describe the first example in which the controlled formation of three distinct kinds of reversible bonds are used to shape the composition of a dynamic combinatorial library, such as the one shown. The dynamic incorporation of a disulfide into dimetallic copper(I) and iron(II) complexes perturbed a disulfide-exchange equilibrium by a factor of up to 179, and this equilibrium could be further manipulated through coordinative (Fe for Cu) or covalent (imine) exchange.

    12. A Convergent Pd-Catalyzed Asymmetric Allylic Alkylation of dl- and meso-Divinylethylene Carbonate: Enantioselective Synthesis of (+)-Australine Hydrochloride and Formal Synthesis of Isoaltholactone (pages 9547–9560)

      Barry M. Trost, Aaron Aponick and Benjamin N. Stanzl

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/chem.200700832

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      Catalytic asymmetric reactions: The palladium-catalyzed asymmetric allylic alkylation of the diastereomeric mixture of dl- and meso-divinylethylene carbonate employing either oxygen or nitrogen nucleophiles yields a single product in high optical purity (see scheme). After further elaboration via selective metathesis reactions (CM: cross-metathesis, RCM: ring-closing metathesis), these useful synthons provide rapid access to 1,2-diol and amino alcohol-derived natural products.

    13. Intermediates in the Destruction of Chlorinated C1 Hydrocarbons on La-Based Materials: Mechanistic Implications (pages 9561–9571)

      Alwies W. A. M. van der Heijden, Maria Garcia Ramos and Bert M. Weckhuysen

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/chem.200700901

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      Surface destruction: The destructive adsorption of CHCl3, CH2Cl2, and CH3Cl on LaOCl was evaluated by in situ IR spectroscopy and gas-flow experiments analyzed with GC. Initially, surface species are formed, which are converted into gas-phase products as the temperature and degree of chlorination of the surface increase (see picture). Conversion of the chlorinated C1 series decreases with increasing hydrogen content of the reactant.

    14. Self-Assembling Phenylpropyl Ether Dendronized Helical Polyphenylacetylenes (pages 9572–9581)

      Virgil Percec, Mihai Peterca, Jonathan G. Rudick, Emad Aqad, Mohammad R. Imam and Paul A. Heiney

      Version of Record online: 24 SEP 2007 | DOI: 10.1002/chem.200701008

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      Helical polymers with known handedness: A new class of self-organizing cylindrical polymers based on phenylpropyl ether based self-assembling dendrons is described (see figure). The helical handedness of these dendronized polyphenylacetylenes has been determined by using the exciton chirality method. Opportunities for the advance of new concepts in sensors and in electronics and to improve understanding of the emergence of macromolecular and supramolecular chirality are presented.

    15. Configurational Stability of Oxymethyllithiums as Intermediates in Intramolecular Rearrangements (pages 9582–9588)

      Dagmar C. Kapeller, Lothar Brecker and Friedrich Hammerschmidt

      Version of Record online: 17 SEP 2007 | DOI: 10.1002/chem.200701054

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      Size doesn't matter! Several oxymethyllithiums [D1]1, the smallest of their kind, have been created and rearranged. They are configurationally stable and lead to products of up to 97 % ee (ee=enantiomeric excess), even at 0 °C.

    16. Asymmetric Total Synthesis of (−)-Indicol by a Carbene Cyclization–Cycloaddition Cascade Strategy (pages 9589–9599)

      Sze Kui Lam and Pauline Chiu

      Version of Record online: 31 AUG 2007 | DOI: 10.1002/chem.200700838

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      Cascade reactions: The first total synthesis of (−)-indicol (see scheme) featured a RhII-mediated carbene cyclization–cycloaddition cascade reaction as the key strategy to construct, in one step, three stereocenters as well as the core bicyclo[5.4.0]undecane framework.

    17. Evidence for the Intermediacy of Wheland–Meisenheimer Complexes in SEAr Reactions of Aminothiazoles with 4,6-Dinitrobenzofuroxan (pages 9600–9607)

      Carla Boga, Erminia Del Vecchio, Luciano Forlani, Régis Goumont, François Terrier and Silvia Tozzi

      Version of Record online: 17 SEP 2007 | DOI: 10.1002/chem.200700669

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      Successful identification of a Wheland–Meisenheimer complex by NMR: The reactions between DNBF and a series of 2-aminothiazoles to afford thermodynamically stable C-bonded σ-adducts have been investigated. Evidence that the Wheland–Meisenheimer complex WM-1 a is the key intermediate has been obtained by NMR spectroscopic experiments.

    18. Unusual Coexistence of Magnetic and Nonmagnetic Mo6 Octahedral Clusters in a Chalcohalide Solid Solution: Synthesis, X-ray Diffraction, EPR, and DFT Investigations of Cs3Mo6Ii6Ii2−xSeixIa6 (pages 9608–9616)

      Kaplan Kirakci, Stéphane Cordier, Alex Shames, Bruno Fontaine, Olivier Hernandez, Eric Furet, Jean-François Halet, Régis Gautier and Christiane Perrin

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/chem.200700370

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      They're together (what a surprise!): The structure of Cs3Mo6Ii6Ii2−xSexIa6 (as illustrated) is based on a mixture of (x−1) magnetic [Mo6Ii6Sei2Ia6]3− units coexisting with (2−x) [Mo6Ii7SeiIa6]3− diamagnetic units with 23 and 24 valence electrons per Mo6 cluster respectively (1.2≤x≤1.6).

    19. On the Characterization of Dynamic Supramolecular Systems: A General Mathematical Association Model for Linear Supramolecular Copolymers and Application on a Complex Two-Component Hydrogen-Bonding System (pages 9617–9636)

      Fabrice G. J. Odille, Stefán Jónsson, Susann Stjernqvist, Tobias Rydén and Kenneth Wärnmark

      Version of Record online: 17 SEP 2007 | DOI: 10.1002/chem.200700032

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      Characterization of supramolecular systems: A general mathematical model for the characterization of the dynamic (kinetically labile) association of supramolecular assemblies in solution is presented (see scheme). The derived mathematical methodology makes it possible to analyze dynamic systems such as supramolecular copolymers regarding, for instance, the degree of polymerization, the distribution of a given monomer in different copolymers and its position in an aggregate.

    20. Bis[bis-(4-alkoxyphenyl)amino] Derivatives of Dithienylethene, Bithiophene, Dithienothiophene and Dithienopyrrole: Palladium-Catalysed Synthesis and Highly Delocalised Radical Cations (pages 9637–9646)

      Susan A. Odom, Kelly Lancaster, Luca Beverina, Kelly M. Lefler, Natalie J. Thompson, Veaceslav Coropceanu, Jean-Luc Brédas, Seth R. Marder and Stephen Barlow

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/chem.200700668

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      Radical cations of diamines containing thiophene-based bridges (see figure) exhibit near-IR absorptions characteristic of strongly delocalised species. ESR spectroscopy and DFT indicate that, relative to species with analogous hydrocarbon bridges, the bridge character of the oxidation is increased at the expense of the nitrogen-based character.

    21. Copper-Catalyzed Asymmetric Conjugate Addition of Trialkylaluminium Reagents to Trisubstituted Enones: Construction of Chiral Quaternary Centers (pages 9647–9662)

      Magali Vuagnoux-d'Augustin and Alexandre Alexakis

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/chem.200701001

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      The enantioselective Cu-catalyzed conjugate addition of Me3Al, Et3Al, and vinylalane species to a wide range of substituted enones in the presence of chiral phosphoramidite ligands is described (see scheme). Chiral quaternary centers can be built with up to 98 % ee. Then, enantioenriched aluminium enolates and chiral adducts were functionalized and used for subsequent reactions.

    22. Contrasting pKa of Protonated Bis(3-aminopropyl)-Terminated Polyethylene Glycol “Jeffamine” and the Associated Thermodynamic Parameters in Solution and Covalently Attached to Graphite Surfaces (pages 9663–9667)

      Poobalasingam Abiman, Gregory G. Wildgoose, Alison Crossley, John H. Jones and Richard G. Compton

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/chem.200700942

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      Potentiometric titration has been used to determine the pKa value of protonated Jeffamine (bis(3-aminopropyl)-terminated polyethylene glycol) in solution and attached as a monolayer to graphite surfaces (see scheme).

    23. How Strong Are Hydrogen Bonds in Metalla-β-diketones? (pages 9668–9678)

      Dirk Steinborn and Sebastian Schwieger

      Version of Record online: 25 SEP 2007 | DOI: 10.1002/chem.200700666

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      Strong intramolecular O[BOND]H⋅⋅⋅O hydrogen bonds have been found by DFT calculations on metalla-β-diketones I, their open equilibrium conformers (hydroxycarbene acyl complexes II), and open conformers obtained by rigid rotation of the OH group by 180° and subsequent constrained relaxation (frozen dihedral angles, III). These hydrogen bonds are up to twice as strong as that in the enol form of acetylacetone, the “generic” organic β-diketone.

    24. The Isolation of Basic Proteins by Solid-Phase Extraction with Multiwalled Carbon Nanotubes (pages 9679–9685)

      Zhuo Du, Yong-Liang Yu, Xu-Wei Chen and Jian-Hua Wang

      Version of Record online: 13 SEP 2007 | DOI: 10.1002/chem.200700784

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      Selective separation of individual protein species: Multiwalled carbon nanotubes (MWCNTs) have been employed for the first time as sorbents for the isolation of basic proteins from other protein species (see graphic; +/−: proteins). Hemoglobin and cytochrome c retained on a MWCNT-packed microcolumn were separated by sequential elution with a phosphate buffer (0.025 mol L−1) and a NaCl solution (0.5 mol L−1), respectively.

    25. Chameleon Reactivity of the Allene Bond of 4-Vinylidene-2-oxazolidinone: Novel Through-Space Conjugative Nucleophilic Addition of Electron-Rich Alkenes and Hetero-Nucleophiles (pages 9686–9702)

      Masanari Kimura, Yoshikazu Horino, Masahiko Mori and Yoshinao Tamaru

      Version of Record online: 4 SEP 2007 | DOI: 10.1002/chem.200700691

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      Through-space conjugative attack by neutral C-, O-, and S-nucleophiles upon Cβ (see scheme) causes N[BOND]SO2 bond cleavage of 1 and sulfonyl group migration from N to Cα to generate 3-sulfonyl-1-aza-1,3-butadiene, a reactive 4π-component intermediate for the inverse electron demand Diels–Alder reaction.

    26. Synthesis, DNA-Binding, Cleavage, and Cytotoxic Activity of New 1,7-Dioxa-4,10-diazacyclododecane Artificial Receptors Containing Bisguanidinoethyl or Diaminoethyl Double Side Arms (pages 9703–9712)

      Xin Sheng, Xiao-Min Lu, Yue-Ting Chen, Guo-Yuan Lu, Jing-Jing Zhang, Ying Shao, Fang Liu and Qiang Xu

      Version of Record online: 11 SEP 2007 | DOI: 10.1002/chem.200700549

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      Powerful nuclease activity is exhibited by 1,7-dioxa-4,10-diazacyclododecane artificial receptors with two pendant functional (bisguanidinium or diamino) side arms (SNase mimic; see picture). The acceleration of DNA hydrolysis can be attributed to the efficient cooperative catalysis of the copper cation center and the functional groups.

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      Preview: Chem. Eur. J. 35/2007 (page 9719)

      Version of Record online: 16 NOV 2007 | DOI: 10.1002/chem.200790133

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