Chemistry - A European Journal

Cover image for Vol. 14 Issue 30

October 20, 2008

Volume 14, Issue 30

Pages 9083–9447

  1. Cover Picture

    1. Top of page
    2. Cover Picture
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Preview
    1. Cover Picture: Switchable Nanoassemblies from Macroions and Multivalent Dye Counterions (Chem. Eur. J. 30/2008) (page 9083)

      Immanuel Willerich and Franziska Gröhn

      Version of Record online: 10 OCT 2008 | DOI: 10.1002/chem.200890119

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      Electrostatic self-assembly in aqueous solution allows formation of supramolecular cylindrical structures that can be switched “on” and “off” by pH. One can reversibly switch between 5 nm building blocks and defined 150 nm assemblies. The system presented in the Communication by I. Willerich and F. Gröhn on page 9112 ff., consists of dendrimer macroions that become interconnected through multivalent dye counterions. Thereby a new concept for the formation of supramolecular structures in solution is demonstrated. It may open a field of versatile functional and responsive nanostructures in aqueous solution.

  2. Graphical Abstract

    1. Top of page
    2. Cover Picture
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Preview
  3. News

    1. Top of page
    2. Cover Picture
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Preview
  4. Concept

    1. Top of page
    2. Cover Picture
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Preview
    1. Bioorganic Chemistry

      Chemical Defence Strategies of Higher Fungi (pages 9100–9110)

      Peter Spiteller

      Version of Record online: 7 JUL 2008 | DOI: 10.1002/chem.200800292

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      Defensive: Higher fungi have evolved a huge variety of defence strategies based on toxins, fungicides or bitter tasting compounds which are either present permanently or are produced only upon injury (see figure). In this paper different methods for the identification of defence compounds and the elucidation of defence mechanisms are discussed.

  5. Communications

    1. Top of page
    2. Cover Picture
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Preview
    1. Electrostatic Self-Assembly

      Switchable Nanoassemblies from Macroions and Multivalent Dye Counterions (pages 9112–9116)

      Immanuel Willerich and Franziska Gröhn

      Version of Record online: 24 SEP 2008 | DOI: 10.1002/chem.200801167

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      Switching aggregation on and off: Electrostatic self-assembly in aqueous solution allows formation of supramolecular structures that can be switched “on” and “off” by pH. Thereby a reversible change between 5 nm building blocks and 150 nm assemblies occurs, while the color of the solution switches between red and yellow (see figure). The system presented consists of dendrimer macroions connected by multivalent dye counterions.

    2. Molecular Magnetism

      Ground Spin State Changes and 3 D Networks of Exchange Coupled [MnIII3] Single-Molecule Magnets (pages 9117–9121)

      Ross Inglis, Leigh F. Jones, Kevin Mason, Anna Collins, Stephen A. Moggach, Simon Parsons, Spyros P. Perlepes, Wolfgang Wernsdorfer and Euan K. Brechin

      Version of Record online: 3 SEP 2008 | DOI: 10.1002/chem.200801266

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      A biased spin doctor: Structural distortions change the intramolecular exchange from antiferromagnetic to ferromagnetic, producing a range of 3D networks of [MnIII3] exchange-coupled single-molecule magnets (SMMs, 16), which demonstrate that quantum tunnelling of magnetisation (QTM) can be controlled using exchange interactions. This opens up new perspectives in the use of supramolecular chemistry to modulate the quantum physics of molecular nanomagnets.

    3. Polymers

      Transfer of Supramolecular Chirality in Block Copoly(thiophene)s (pages 9122–9125)

      Karlien Van den Bergh, Jurgen Huybrechts, Thierry Verbiest and Guy Koeckelberghs

      Version of Record online: 12 SEP 2008 | DOI: 10.1002/chem.200801537

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      Line up! A block copolymer, composed of an (achiral) poly(3-hexylthiophene) and a chiral, poly(3-(3,7-dimethyloctyloxy)thiophene) was prepared. It was shown that the chiral block transfers its supramolecular chirality to the achiral block, demonstrating that the blocks influence their mutual supramolecular organization (see figure).

    4. Nanoparticles

      A New Method for the Rapid Synthesis of Water Stable Superparamagnetic Nanoparticles (pages 9126–9130)

      Fernando Herranz, M. Puerto Morales, Alejandro G. Roca, Manuel Desco and Jesús Ruiz-Cabello

      Version of Record online: 12 SEP 2008 | DOI: 10.1002/chem.200800755

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      Small changes—big effect: Superparamagnetic nanoparticles stable in water with mean hydrodynamic sizes of 37 and 70 nm have been obtained by small changes in the experimental setup (see figure). The particles show a great stability in water and a narrow size distribution. This new approach can be used not only as a standard procedure for the synthesis of hydrophillic nanoparticles, but as the starting point for further modifications of particle surfaces for molecular imaging applications.

    5. Tandem Reactions

      Unprecedented Consecutive, Competitive Nucleophilic Addition to Construct Densely Functionalized Propargylic Alcohols (pages 9131–9134)

      Jie Liu, Yan An, Ya-Hui Wang, Hai-Ying Jiang, Yu-Xin Zhang and Zili Chen

      Version of Record online: 9 SEP 2008 | DOI: 10.1002/chem.200801452

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      Two for the price of one: A new tandem reaction involving two consecutive, competitive nucleophilic additions was developed to construct a series of densely functionalized propargylic alcohol derivatives from simple materials without functional protection, in which a variety of electrophiles including cyclopropanone and aromatic aldehydes have been successfully employed. Multiple functionalities in products 1 and 2 make them versatile structural motifs for further elaboration.

    6. RNA Synthesis

      A Base-Labile Group for 2′-OH Protection of Ribonucleosides: A Major Challenge for RNA Synthesis (pages 9135–9138)

      Thomas Lavergne, Jean-Rémi Bertrand, Jean-Jacques Vasseur and Françoise Debart

      Version of Record online: 2 SEP 2008 | DOI: 10.1002/chem.200801392

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      A novel methodology that disrupts the dogma “RNA synthesis is incompatible with a whole base-labile strategy” has been developed. In this strategy (see scheme), 2′-OH groups are protected by pivaloyloxymethyl groups, compatible with standard base-labile protections for nucleobases and phosphates. Protecting groups are removed in a short two-step all-base procedure to afford RNA efficiently, rapidly, and in high purity without chain rupture or isomerization.

    7. Heterocycles

      One-Pot Synthesis of Fused Tricyclic Heterocycles with Quaternary Carbon Stereocenter by Sequential Pauson–Khand Reaction and Formal [3+3] Cycloaddition (pages 9139–9142)

      Liyan Fan, Wanxiang Zhao, Weihua Jiang and Junliang Zhang

      Version of Record online: 9 SEP 2008 | DOI: 10.1002/chem.200801453

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      “Quick-step” synthesis: Very few steps are needed to make these target tricylic ring systems (see scheme, left) from readily available functionalized acyclic starting materials (right). Target complex ring systems, such as these, can be synthesized efficiently and with high atom-economy using a novel ‘one-pot’, sequential Pauson–Khand reaction of 1-ene-6,8-diynes with CO and a formal [3+3] cycloaddition of the cycloadduct with β-keto compounds.

    8. Organocatalysis

      Amino Acid-Catalyzed Cascade [3+2]-Cycloaddition/Hydrolysis Reactions Based on the Push–Pull Dienamine Platform: Synthesis of Highly Functionalized NH-1,2,3-Triazoles (pages 9143–9147)

      Dhevalapally B. Ramachary, Kinthada Ramakumar and Vidadala V. Narayana

      Version of Record online: 2 SEP 2008 | DOI: 10.1002/chem.200801325

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      Cascade reactions! A practical and environmentally friendly amino acid catalyzed cascade process for the synthesis of highly substituted NH-1,2,3-triazoles was achieved for the first time through cascade [3+2]-cycloaddition/hydrolysis of Hagemann's esters with p-toluenesulfonyl azide (TsN3) in the presence of a catalytic amount of proline (see scheme).

  6. Full Papers

    1. Top of page
    2. Cover Picture
    3. Graphical Abstract
    4. News
    5. Concept
    6. Communications
    7. Full Papers
    8. Preview
    1. Asymmetric Catalysis

      New Benzo[h]quinoline-Based Ligands and their Pincer Ru and Os Complexes for Efficient Catalytic Transfer Hydrogenation of Carbonyl Compounds (pages 9148–9160)

      Walter Baratta, Maurizio Ballico, Salvatore Baldino, Giorgio Chelucci, Eberhardt Herdtweck, Katia Siega, Santo Magnolia and Pierluigi Rigo

      Version of Record online: 18 SEP 2008 | DOI: 10.1002/chem.200800888

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      The terdentate ortho-metalated complexes [MX(CN′N)(P2)] (M=Ru, Os; X=Cl, H, OR; P=PPh3 or P2=diphosphane; an example is illustrated here), prepared from novel 2-aminomethylbenzo[h]quinoline-type ligands (HCN′N), are extremely active and productive catalysts (TOF up to 1.8 ×106 h−1 at 0.02–0.001 mol % loading) for the transfer hydrogenation of carbonyl compounds.

    2. Lipophilicity

      Novel Guanidine-Containing Molecular Transporters Based on Lactose Scaffolds: Lipophilicity Effect on the Intracellular Organellar Selectivity (pages 9161–9168)

      Goutam Biswas, Ock-Youm Jeon, Woo Sirl Lee, Dong-Chan Kim, Kyong-Tai Kim, Suho Lee, Sunghoe Chang and Sung-Kee Chung

      Version of Record online: 3 SEP 2008 | DOI: 10.1002/chem.200801160

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      Drug-delivery vehicles: Two lactose-based G7 molecular transporters with different linker chain lengths were synthesized (see scheme, FITC=fluorescein isothiocyanate). They showed good cellular uptake and preferential localization either in mitochondria or in lysosomes and endocytic vesicles, depending on their chain lengths.

    3. Hydrogenation

      Investigation of a Possible Solvent Cage Effect in the Reduction of 4-Aminocyclohexanone by a Hydroxycyclopentadienyl Ruthenium Hydride (pages 9169–9174)

      Jenny B. Åberg and Jan-E. Bäckvall

      Version of Record online: 24 SEP 2008 | DOI: 10.1002/chem.200801195

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      No solvent cage effect was observed in the reduction of aminoketone 3 with Ru hydride 2. If there were a strong cage effect the ruthenium complex A in a cage complex C would be preferentially trapped by aminoalcohol 4. However, the results show that A is trapped also by Ru hydride 2 and aminoketone 3. The statistical distribution between trapping products 1, 5, and 7 observed shows that there is no cage effect.

    4. Homogeneous Catalysis

      Mechanism of the Palladium-Catalyzed Carbohydroxylation of Allene-Substituted Conjugated Dienes: Rationalization of the Recently Observed Nucleophilic Attack by Water on a (π-Allyl)palladium Intermediate (pages 9175–9180)

      Erik A. Karlsson and Jan-E. Bäckvall

      Version of Record online: 24 SEP 2008 | DOI: 10.1002/chem.200801294

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      Reactions in water: The mechanism of the palladium-catalyzed carbohydroxylation of allene-substituted conjugated diene 1 in water to give 2 has been studied by DFT calculations. All previously proposed intermediates were confirmed and all the transition states for the reaction pathway were located.

    5. Natural Products

      A Gold-Catalyzed Entry into the Sesquisabinene and Sesquithujene Families of Terpenoids and Formal Total Syntheses of Cedrene and Cedrol (pages 9181–9191)

      Alois Fürstner and Andreas Schlecker

      Version of Record online: 11 SEP 2008 | DOI: 10.1002/chem.200801382

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      A cosmos of variously functionalized terpenes of the sesquisabina and sesquithuja families is accessible by a sequence of asymmetric allylation and gold-catalyzed cycloisomerization as the key steps. These syntheses allowed the previously unknown stereostructures of several such bicyclic terpenes to be firmly established.

    6. Uranium Complexes

      Reactions of Uranium Atoms with Ammonia: Infrared Spectra and Quasi-Relativistic Calculations of the U:NH3, H2N[BOND]UH, and HN[DOUBLE BOND]UH2 Complexes (pages 9192–9201)

      Xuefeng Wang, Lester Andrews and Colin J. Marsden

      Version of Record online: 2 SEP 2008 | DOI: 10.1002/chem.200800875

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      Evidence for uranimine: Uranium atoms react with ammonia to form the U:NH3 complex, which rearranges upon visible irradiation to form the amino uranium hydride and the imino uranium dihydride molecules in excess argon (see figure).

    7. Dendrimers

      A Convergent Approach to Biocompatible Polyglycerol “Click” Dendrons for the Synthesis of Modular Core–Shell Architectures and Their Transport Behavior (pages 9202–9214)

      Monika Wyszogrodzka and Rainer Haag

      Version of Record online: 3 SEP 2008 | DOI: 10.1002/chem.200800892

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      Click, click, click… A highly efficient metal-free route to bifunctional glycerol dendrons is presented in which the reactive hydroxy-functionalized focal points of the dendrons were converted to the corresponding azides. These in turn could be used for copper-catalyzed 1,3-dipolar cycloaddition (“click” coupling) with oligoacetylene aromatic core units to give core–shell structures as shown in the picture.

    8. Cyclophanes

      Cyclophane-Type Imidazolium Salts with Planar Chirality as a New Class of N-Heterocyclic Carbene Precursors (pages 9215–9222)

      Yuki Matsuoka, Yasuhiro Ishida, Daisuke Sasaki and Kazuhiko Saigo

      Version of Record online: 27 AUG 2008 | DOI: 10.1002/chem.200800942

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      Controlled chirality: Cyclophane-type imidazolium salts with planar chirality (see scheme) were developed as N-heterocyclic carbene precursors. These were found to catalyze the asymmetric cross-annulation of an α,β-unsaturated aldehyde with a ketone through the “conjugated” umpolung of the enal to give γ-lactone with good to excellent enantioselectivity.

    9. Polyoxometalates

      Combination of Lacunary Polyoxometalates and High-Nuclear Transition Metal Clusters under Hydrothermal Conditions: IX. A Series of Novel Polyoxotungstates Sandwiched by Octa-Copper Clusters (pages 9223–9239)

      Jun-Wei Zhao, Chun-Mei Wang, Jie Zhang, Shou-Tian Zheng and Guo-Yu Yang

      Version of Record online: 21 AUG 2008 | DOI: 10.1002/chem.200800856

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      Sandwiches anyone? The combination of two trivacant Keggin fragments and one high-nuclear {Cu8} cluster, formed in situ under hydrothermal conditions, results in a series of 0D, 2D, and 3D sandwich-type polyoxometalates. In addition, the rollover metalation of 2,2′-bpy was observed in the presence of low-priced CuII ions (see figure).

    10. Reaction Mechanisms

      Aldol Reactions between L-Erythrulose Derivatives and Chiral α-Amino and α-Fluoro Aldehydes: Competition between Felkin–Anh and Cornforth Transition States (pages 9240–9254)

      Santiago Díaz-Oltra, Miguel Carda, Juan Murga, Eva Falomir and J. Alberto Marco

      Version of Record online: 29 AUG 2008 | DOI: 10.1002/chem.200800956

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      Strict adherence to the Felkin–Anh model for the transition structures does not account satisfactorily for all the observed results of aldol reactions of a chiral boron enolate with chiral α-fluoro and α-amino aldehydes (see scheme). In some cases, only the Cornforth model provides a good explanation. The factors that influence this dichotomy are studied with the aid of density functional calculations.

    11. Layered Host Compounds

      New Layered Rare-Earth Hydroxides with Anion-Exchange Properties (pages 9255–9260)

      Fengxia Geng, Hao Xin, Yoshitaka Matsushita, Renzhi Ma, Masahiko Tanaka, Fujio Izumi, Nobuo Iyi and Takayoshi Sasaki

      Version of Record online: 27 AUG 2008 | DOI: 10.1002/chem.200800127

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      A sandwich with changeable fillings: A layered rare-earth hydroxide comprising a positively charged layer of [RE8(OH)20(H2O)6.4]4+ (RE: Eu, Tb, etc.) and interlayer Cl ions (see structure) was successfully synthesized by homogeneous precipitation. The Cl ions were readily exchangeable for various anions (NO3, SO42−, dodecylsulfonate, etc.) at room temperature.

    12. Organogels

      Strength Enhancement of Nanostructured Organogels through Inclusion of Phthalocyanine-Containing Complementary Organogelator Structures and In Situ Cross-Linking by Click Chemistry (pages 9261–9273)

      David Díaz Díaz, Juan José Cid, Purificación Vázquez and Tomás Torres

      Version of Record online: 26 AUG 2008 | DOI: 10.1002/chem.200800714

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      Photoactive organogels: Photoactive organogels based on phthalocyanine moieties containing complementary organogelator structures were synthesised (see figure). Strength enhancement of the gels was achieved by in situ cross-linking by click chemistry based on CuI-catalysed azide–alkyne [3+2] cycloadditions.

    13. Reaction mechanisms

      Theoretical Insights into Enantioselective Catalysis: The Mechanism of the Kharasch–Sosnovsky Reaction (pages 9274–9285)

      José Antonio Mayoral, Sergio Rodríguez-Rodríguez and Luis Salvatella

      Version of Record online: 29 AUG 2008 | DOI: 10.1002/chem.200800638

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      A new reaction mechanism for the Kharasch–Sosnovsky reaction is proposed in agreement with theoretical calculations. The mechanism involves the intramolecular hydrogen transfer of an alkene-copper(III) complex leading to the formation of an allyl-copper(III) reaction intermediate (see figure), which can alternatively undergo either an haptotropic rearrangement (leading to the scrambling between vinylic and allylic carbon atoms) or a reductive elimination (yielding the final reaction product).

    14. Click Chemistry

      Electrochemical Functionalization of Carbon Surfaces by Aromatic Azide or Alkyne Molecules: A Versatile Platform for Click Chemistry (pages 9286–9291)

      David Evrard, François Lambert, Clotilde Policar, Véronique Balland and Benoît Limoges

      Version of Record online: 9 SEP 2008 | DOI: 10.1002/chem.200801168

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      Graft and click! Phenylazide or phenylacetylene groups were electrochemically grafted onto the surface of carbon electrodes and coupled with compounds bearing an acetylene or azide function to form a covalent 1,2,3-triazole linkage by means of click chemistry (see figure). This was illustrated with the surface coupling of ferrocene redox probes and biotin.

    15. Reaction Mechanisms

      Predicting Reactivity and Stereoselectivity in the Nazarov Reaction: A Combined Computational and Experimental Study (pages 9292–9304)

      Andrea Cavalli, Alessandro Pacetti, Maurizio Recanatini, Cristina Prandi, Dina Scarpi and Ernesto G. Occhiato

      Version of Record online: 27 AUG 2008 | DOI: 10.1002/chem.200801030

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      Combining theory and experiments: A combined DFT and experimental study on the Nazarov reaction involving N- and S-heterocycles showed that both heteroatoms are capable of accelerating ring closure by stabilizing the partial positive charge in the transition state (see scheme). High stereoselectivity was obtained with substituted N-heterocycles, whereas with S-heterocyclic derivatives torquoselectivity was very low.

    16. Ionic Liquids

      Long-Alkyl-Chain Quaternary Ammonium Lactate Based Ionic Liquids (pages 9305–9311)

      Jacek Cybulski, Anna Wiśniewska, Anna Kulig-Adamiak, Lidia Lewicka, Anna Cieniecka-Rosłonkiewicz, Kazimierz Kita, Andrzej Fojutowski, Jan Nawrot, Katarzyna Materna and Juliusz Pernak

      Version of Record online: 26 AUG 2008 | DOI: 10.1002/chem.200800973

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      A novel group of ionic liquids! Lactate-based ionic liquids are cheap, multifunctional, and environmentally friendly. Didecyldimethylammonium and benzalkonium lactates have been found to be very effective antibacterial and antifungal agents (see graphic). Moreover, they have also been shown to be good insect-feeding deterrents. Their acute oral toxicity has also been studied and the toxicological data are presented.

    17. Heterocycles

      Metal-Free and PdII-Promoted [2+3] Cycloadditions of a Cyclic Nitrone to Phthalonitriles: Syntheses of Oxadiazolines as well as Phthalamide–PdII and Dihydropyrrolyl-iminoisoindolinone–PdII Complexes with High Catalytic Activity in Suzuki–Miyaura Cross-Coupling Reactions (pages 9312–9322)

      Jamal Lasri, Maximilian N. Kopylovich, M. Fátima C. Guedes da Silva, M. Adília Januário Charmier and Armando J. L. Pombeiro

      Version of Record online: 26 AUG 2008 | DOI: 10.1002/chem.200800510

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      Active cycles: Addition of a cyclic nitrone to a phthalonitrile in the absence or presence of PdCl2 provides a convenient route to novel heterocycles such as 2-oxadiazolyl-benzonitriles, ortho-bis(oxadiazolyl)benzene, and bis(pyrrolidin-2-ylidene)phthalamide–PdII complexes and the first examples of dihydropyrrolyl-iminoisoindolinone–PdII compounds, respectively (see scheme). The PdII complexes show a very high catalytic activity in the the Suzuki–Miyaura cross-coupling reaction (turnover frequency (TOF) up to 9.0×105 h−1).

    18. Asymmetric Synthesis

      Enantioselective Synthesis of [7]Helicene: Dramatic Effects of Olefin Additives and Aromatic Solvents in Asymmetric Olefin Metathesis (pages 9323–9329)

      Alain Grandbois and Shawn K. Collins

      Version of Record online: 26 AUG 2008 | DOI: 10.1002/chem.200801033

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      Helical chirality: The asymmetric synthesis of [7]helicene was accomplished by using new Ru-based olefin metathesis catalysts bearing C1-symmetric N-heterocyclic carbene ligands, simple olefins as additives to control the nature of the propagating alkylidene and hexafluorobenzene as a solvent (see scheme).

    19. Metathesis

      Is the Hoveyda–Grubbs Complex a Vinylogous Fischer-Type Carbene? Aromaticity-Controlled Activity of Ruthenium Metathesis Catalysts (pages 9330–9337)

      Michał Barbasiewicz, Anna Szadkowska, Anna Makal, Katarzyna Jarzembska, Krzysztof Woźniak and Karol Grela

      Version of Record online: 3 SEP 2008 | DOI: 10.1002/chem.200800704

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      Aromaticity [Ru]les! Novel benzoanalogues of the Hoveyda–Grubbs metathesis catalyst exhibit unexpected differences in reactivity (see scheme). Structural studies and topological analyses reveal that aromatic conjugation within the ruthenium chelate ring, which is governed by the ligand core, is a source of this phenomenon. The concept explains properties of 2-alkoxybenzylidene ligands and their substituent effects in metathesis catalysts.

    20. Supramolecular Chemistry

      An Enolisable Barbiturate with Adjustable Hydrogen-Bonding Structure for UV/Vis Detection of Nucleic Acid Bases and Related Compounds (pages 9338–9346)

      Ina Bolz and Stefan Spange

      Version of Record online: 29 AUG 2008 | DOI: 10.1002/chem.200800626

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      A discriminating probe: The enolisable barbiturate 1-n-butyl-5-(4-nitrophenyl)barbituric acid (1) presents new opportunities for the simultaneous spectroscopic determination of polarity changes, acid–base reactions and complex formation with complementary hydrogen-bonding patterns, through its hydrogen-bonding ability, acidity and potential solvatochromic effects.

    21. Half-Sandwich Complexes

      Reactions of 16e CpCo Half-Sandwich Complexes Containing a Chelating 1,2-Dicarba-closo-dodecaborane-1,2-dichalcogenolate Ligand with Ethynylferrocene and Dimethyl Acetylenedicarboxylate (pages 9347–9356)

      Bao-Hua Xu, Xu-Qing Peng, Yi-Zhi Li and Hong Yan

      Version of Record online: 2 SEP 2008 | DOI: 10.1002/chem.200801136

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      Sandwich course: Reaction of 1 S with HC[TRIPLE BOND]C[BOND]Fc (Fc: ferrocenyl) leads to 2 S, which converts to 3 S and 4 S in MeOH (see scheme). However, in the case of MeO2CC[TRIPLE BOND]CCO2Me, the stepwise substitution of the o-carborane cage at the B(3)/B(6)-positions leads to 7 S and 9 S, respectively.

    22. Organocatalysis

      Organocatalytic Enantioselective Synthesis of Highly Functionalized Polysubstituted Pyrrolidines (pages 9357–9367)

      Nerea Ruiz, Efraím Reyes, Jose L. Vicario, Dolores Badía, Luisa Carrillo and Uxue Uria

      Version of Record online: 2 SEP 2008 | DOI: 10.1002/chem.200800788

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      Asymmetric organocatalysis: An improved procedure has been optimized for carrying out the enantioselective Michael reaction between β-nitroacrolein dimethyl acetal and a variety of aldehydes. The obtained adducts have been converted into enantiopure highly functionalized pyrrolidines containing two or three contiguous stereocenters (see scheme) by way of two short and efficient protocols.

    23. Lipooligosaccharides

      Highly Phosphorylated Core Oligosaccaride Structures from Cold-Adapted Psychromonas arctica (pages 9368–9376)

      Maria M. Corsaro, Giuseppina Pieretti, Buko Lindner, Rosa Lanzetta, Ermenegilda Parrilli, Maria L. Tutino and Michelangelo Parrilli

      Version of Record online: 3 SEP 2008 | DOI: 10.1002/chem.200800117

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      Highly negative charged core: The structure of the carbohydrate backbone of the lipooligosaccharide (see picture) from the cold-adapted bacterium Psychromonas arctica has been characterised after mild and strong alkaline hydrolysis. This structure represents the second core structure described for a lipooligosaccharide of a cold-adapted bacterium.

    24. O[BOND]O Activation

      A Dinuclear Iron Complex Based on Parallel Malonate Binding Sites: Cooperative Activation of Dioxygen and Biomimetic Ligand Oxidation (pages 9377–9388)

      Inke Siewert, Christian Limberg, Serhiy Demeshko and Elke Hoppe

      Version of Record online: 12 SEP 2008 | DOI: 10.1002/chem.200800955

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      Biomimetic O2activation: A complex in which two iron centres are complexed by two ligands bearing parallel malonate binding pockets (see picture for crystal structure; Fe orange, O red, C grey, H omitted) activates O2 and then undergoes ligand oxidation to give alcohols, peroxides and α-keto esters. A reaction mechanism is suggested in which some steps mimic the proposed functioning of non-heme Fe enzymes.

    25. Energy Transfer

      On the Mechanism of d–f Energy Transfer in RuII/LnIII and OsII/LnIII Dyads: Dexter-Type Energy Transfer Over a Distance of 20 Å (pages 9389–9399)

      Theodore Lazarides, Daniel Sykes, Stephen Faulkner, Andrea Barbieri and Michael D. Ward

      Version of Record online: 29 AUG 2008 | DOI: 10.1002/chem.200800600

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      d–f Dyads: A series of RuII and OsII tris-bipyridyl chromophores, containing a pendant bipyridyl site to which a LnIII tris(diketonate) fragment can bind (see picture), was used to investigate the mechanism of RuII[RIGHTWARDS ARROW]LnIII and OsII[RIGHTWARDS ARROW]LnIII photoinduced energy transfer as a function of distance, and as a function of saturation/unsaturation in the bridging pathway. We found unequivocal evidence that the energy transfer occurs by a bridging-ligand-mediated exchange mechanism over distances up to 20 Å as long as a conjugated bridge is used.

    26. Glycosylation

      Stereoselective Synthesis of L-Guluronic Acid Alginates (pages 9400–9411)

      Jasper Dinkelaar, Leendert J. van den Bos, Wouter F. J. Hogendorf, Gerrit Lodder, Herman S. Overkleeft, Jeroen D. C. Codée and Gijsbert A. van der Marel

      Version of Record online: 3 SEP 2008 | DOI: 10.1002/chem.200800960

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      Highly selective: Building on the unusually high 1,2-cis stereoselectivity of gulopyranosides, a guluronic acid alginate trisaccharide has been assembled for the first time (see scheme). The glycosylation properties of various L-gulose and L-guluronate ester donors have been mapped.

    27. Heterogeneous Catalysis

      Heterogeneous Gold Catalysts for Efficient Access to Functionalized Lactones (pages 9412–9418)

      Florentina Neaţu, Zhi Li, Ryan Richards, Patrick Y. Toullec, Jean-Pierre Genêt, Karifala Dumbuya, J. Michael Gottfried, Hans-Peter Steinrück, Vasile I. Pârvulescu and Véronique Michelet

      Version of Record online: 26 AUG 2008 | DOI: 10.1002/chem.200801327

      Thumbnail image of graphical abstract

      Heterogeneous gold catalysis: Gold supported on zeolite beta-NH4+ (see figure) has been found to catalyze the intramolecular addition of carboxylic acids to alkynes, leading to functionalized lactones. XPS confirmed the role of oxidized Au species in such reactions, and provided evidence regarding the effect of air in preserving the catalyst activity. The heterogeneous catalyst was efficiently recycled four times.

    28. Porphyrinoids

      Interplay between Acetate Ions, Peripheral Groups, and Reactivity of the Core Nitrogens in Transmetalation of Tetrapyrroles (pages 9419–9430)

      Łukasz Orzeł, Leszek Fiedor, Maria Wolak, Agnieszka Kania, Rudi van Eldik and Grażyna Stochel

      Version of Record online: 21 AUG 2008 | DOI: 10.1002/chem.200800991

      Thumbnail image of graphical abstract

      Harnessing metal ions and tetrapyrrolic ligands: New insights into the mechanism of the acetate-induced transmetalation of chlorophylls reveal novel aspects of the interplay between the peripheral groups and the reactivity of the core nitrogen atoms in tetrapyrroles (see scheme).

    29. Antitumor Agents

      Cationic Metal–Corrole Complexes: Design, Synthesis, and Properties of Guanine-Quadruplex Stabilizers (pages 9431–9441)

      Boqiao Fu, Dan Zhang, Xiaocheng Weng, Ming Zhang, Heng Ma, Yuzhi Ma and Xiang Zhou

      Version of Record online: 27 AUG 2008 | DOI: 10.1002/chem.200800835

      Thumbnail image of graphical abstract

      Bringing extra stability: Pyridinium and quaternary ammonium copper corroles (see picture) have been shown to stabilize G-quadruplex structures, of which corrole 2 is the most effective. Moreover, corroles 1 and 2 tend to induce the human telomeric sequence to form hybrid G-quadruplex structures, whereas corroles 3 and 4 are more inclined to induce the human telomeric sequence to form antiparallel G-quadruplex structures.

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      Preview: Chem. Eur. J. 31/2008 (page 9447)

      Version of Record online: 10 OCT 2008 | DOI: 10.1002/chem.200890122

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