Angewandte Chemie International Edition

Cover image for Vol. 42 Issue 15

April 17, 2003

Volume 42, Issue 15

Pages 1671–1773

    1. Cover Picture: Diastereoselective Temporary Silicon-Tethered Ring-Closing-Metathesis Reactions with Prochiral Alcohols: A New Approach to Long-Range Asymmetric Induction (Angew. Chem. Int. Ed. 15/2003) (page 1671)

      P. Andrew Evans, Jian Cui and Gerald P. Buffone

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200390379

      Taking control of stereochemistry should lead to an enhanced understanding of the conformational aspects that affect diastereoselectivity in medium-sized ring systems. The temporary silicon-tethered ring-closing-metathesis reactions described by P. A. Evans et al. on page 1734 ff. represent a new strategy for long-range asymmetric induction that provides a useful approach to 1,4-, 1,5-, and 1,6-stereocontrol.

    2. Web Site: Following the Link of the Least Resistance (page 1682)

      Wojciech Grochala

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200390381

    3. A Solid-State Supramolecular Sweet Spot (pages 1686–1687)

      Bruce C. Gibb

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200201547

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      The beauty of crystals: A bridge between crystals that degrade when their guests are removed and crystalline solids that refuse to release their guests has been provided by Atwood et al. with the report of a calix[4]arene that forms an approximate hexagonal close-packed array of quasi-spherical trimers in the presence and absence of guest molecules (see X-ray crystal structure).

    4. Construction of Quaternary Stereocenters: New Perspectives through Enantioselective Michael Reactions (pages 1688–1690)

      Jens Christoffers and Angelika Baro

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200201614

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      PdII-catalyzed Michael reactions of β-dicarbonyl compounds 1 and enones 2 can generate quaternary stereocenters (shown in yellow) with selectivities of 90 % ee at relatively high temperatures (−10 °C). This method represents a breakthrough in enantioselective synthesis.

    5. Nanotechnology with Soft Materials (pages 1692–1712)

      I. W. Hamley

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200200546

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      It pays to be organized: The intricate structures that can be formed by self-organizing molecules are amazing (see picture). In the next few decades, the creation of a wealth of new materials and devices using soft nanotechnology will be witnessed. This review covers developments to date in fabricating nanostructures and devices using self-organizing polymers, colloids, surfactants, and biomolecules.

    6. Dye Loading of Amphiphilic Poly(organosiloxane) Nanoparticles (pages 1714–1717)

      Nadja Jungmann, Manfred Schmidt, Jochen Ebenhoch, Johann Weis and Michael Maskos

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250288

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      Up to 50 % dye relative to the dead weight may be loaded into poly(organosiloxane) nanoparticles that contain quaternary ammonium groups (vessels 1–3 with hydrophilic thymol blue as a model substance), whereas nanoparticles without quaternary ammonium groups take up no dye (vessels 4, 5). The loading depends inter alia on the construction of the nanoparticles (core–shell, hollow spheres), on the amphiphilicity, which is adjustable by synthesis, and on the method of the phase transfer.

    7. Dianions of Tetraboranes(4): Puckered Aromatic Four-Membered Rings and Their Reactions with Conservation of Aromaticity (pages 1717–1719)

      Wahid Mesbah, Carsten Präsang, Matthias Hofmann, Gertraud Geiseler, Werner Massa and Armin Berndt

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250700

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      Aromatic with boron: Two-electron heteroaromatic compounds 1 and 2 undergo oxidations and reactions with electrophiles (reducing the number of framework electrons by two and four, respectively) under conservation of aromaticity. In contrast, corresponding reactions of the known dianion 3, a six-electron aromatic four-membered ring, lead to loss of aromaticity (R=SiMe3).

    8. Convergent Paired Electrolysis for the Three-Component Synthesis of Protected Homoallylic Alcohols (pages 1720–1721)

      Gerhard Hilt

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200350892

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      The holy grail of electrochemistry, a convergent paired electrolysis, is a step closer in the metal-free electrochemical allylation of aromatic aldehydes in DMF. A three-component coupling product is obtained in a one-pot procedure when anodically generated electrophiles and cathodically generated nucleophiles react in solution to give a single product.

    9. Catalyst–Substrate Coimmobilization: A Strategy for Catalysts Discovery in Split-and-Mix Libraries (pages 1722–1724)

      Philipp Krattiger, Catherine McCarthy, Andreas Pfaltz and Helma Wennemers

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250422

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      Potentially applicable to any bimolecular reaction: A new method for the discovery of catalysts among the members of split-and-mix libraries is described. A reaction partner (A) is immobilized along with each library member (the potential catalyst) on the same bead. The reaction partner B is labeled with a dye, thus a reaction between A and B is easily visualized through the attachment of the marker to the beads that carry the active catalyst.

    10. Efficient Asymmetry Generation in the Synthesis of Oxo-Rhenium(V) Complex cis-[ReOCl2{OCMe2CMe2OP(OCMe2CMe2O)}py] (pages 1725–1727)

      Witold K. Rybak, Anna Skarżyńska and Tadeusz Głowiak

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200219501

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      Its all done without mirrors: A simple procedure that randomly produces enantiomers of an oxo-rhenium(V) complex with a large enantiomeric excess (99 % ee) from optically inactive precursors is presented. The chirally autocatalytic synthesis is achieved by the spontaneous resolution of the conglomerate in a stirred crystallization following the formation of the complex in the reaction system. The results are supported by circular dichroism spectroscopy (see picture).

    11. Proton-Induced Change of the Coordination Mode of a Boron Group: Boryl Complexes [Mn(CO)4(PR3)(BH2⋅PMe3)] and Cationic Borane σ Complexes [Mn(CO)4(PR3)(η1-BH3⋅PMe3)]+ (pages 1727–1730)

      Takahiro Yasue, Yasuro Kawano and Mamoru Shimoi

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200219992

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      Mode change on protonation: New borylmanganese complexes 1 undergo protonation to give cationic borane σ complexes 2. Heterolytic cleavage of the metal-coordinated B[BOND]H bond was observed in the decomposition process of 2.

    12. Photoresponsive Nanocomposite Formed by Self-Assembly of an Azobenzene-Modified Silane (pages 1731–1734)

      Nanguo Liu, Zhu Chen, Darren R. Dunphy, Ying-Bing Jiang, Roger A. Assink and C. Jeffrey Brinker

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250189

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      Organization of photoresponsive azobenzene ligands within a 3D porous framework imparts new molecular-level functionality. The transcis conformation change of azobenzene ligands triggered by photoirradiation transduces photo energy into mechanical work, which can be used for opening and closing valves (see picture).

    13. Diastereoselective Temporary Silicon-Tethered Ring-Closing-Metathesis Reactions with Prochiral Alcohols: A New Approach to Long-Range Asymmetric Induction (pages 1734–1737)

      P. Andrew Evans, Jian Cui and Gerald P. Buffone

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250486

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      A useful approach to 1,4-, 1,5-, and 1,6-stereocontrol, diastereoselective ring-closing-metathesis reactions that utilize temporary silicon tethers represent a new strategy for long-range asymmetric induction. This method facilitates the construction of cis-1,4-silaketals (n=0, d.r.=20:1; see scheme), whereas the extension of this concept to higher alkenyl alcohols (n=1–4) results in a reversal of diastereoselectivity that favors formation of the trans isomer.

    14. You have free access to this content
      Open-Framework Materials Synthesized in the TMA+/TEA+ Mixed-Template System: The New Low Si/Al Ratio Zeolites UZM-4 and UZM-5 (pages 1737–1740)

      C. Scott Blackwell, Robert W. Broach, Michael G. Gatter, Jennifer S. Holmgren, Deng-Yang Jan, Gregory J. Lewis, Beckay J. Mezza, Thomas M. Mezza, Mark A. Miller, Jaime G. Moscoso, R. Lyle Patton, Lisa M. Rohde, Michael W. Schoonover, Wharton Sinkler, Ben A. Wilson and Stephen T. Wilson

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250076

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      The right mix! Combinations of two of the most studied templates in zeolite synthesis, the tetramethylammonium (TMA+) and tetraethylammonium (TEA+) ions, are employed to synthesize the new species UZM-4, a stable large-pore zeolite with the BPH toplogy, and UZM-5, which has a new framework topology related to zeolite A in two dimensions and large surface cups capable of catalysis of aromatic compounds.

    15. Structure of a Self-Assembled Chain of Water Molecules in a Crystal Host (pages 1741–1743)

      Satyanarayan Pal, N. B. Sankaran and Anunay Samanta

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250444

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      The role of hydrogen bonding in water is important in determining the structure, stability, and function of biological assemblies. The supramolecular structure of 1,4,7,10-tetraazacyclododecane, a molecule that has secondary N[BOND]H bonds similar to those found in biological systems, contains an infinite chain of tetrameric water clusters (depicted, oxygen: red; hydrogen: white). This motif, until now, has not even been speculated upon.

    16. Controlled Living Ring-Opening-Metathesis Polymerization by a Fast-Initiating Ruthenium Catalyst (pages 1743–1746)

      Tae-Lim Choi and Robert H. Grubbs

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250632

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      Highly active with ultrafast initiation, the catalyst 1 promotes the controlled, living, ring-opening polymerization of various norbornene and 7-oxonorbornene derivatives (see scheme). The high ki/kp ratio associated with the polymerization reactions results in better molecular-weight control and narrower polydispersity indexes (PDIs, ki=rate constant for initiation, kp=rate constant for polymerization).

    17. Solid-State Supramolecular Chirogenesis: High Optical Activity and Gradual Development of Zinc Octaethylporphyrin Aggregates (pages 1746–1749)

      Victor V. Borovkov, Takunori Harada, Guy A. Hembury, Yoshihisa Inoue and Reiko Kuroda

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250524

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      Slow formation of J-type helical aggregates occurs when the simple achiral zinc octaethylporphyrin interacts with enantiopure 1-cyclohexylethylamines in the solid state. These chiral solid-state aggregates exhibit a high degree of optical activity and are remarkably stable, as evidenced in the circular dichroism spectra (see picture).

    18. Bromoallenes as Synthetic Equivalents of Allyl Dications: Synthesis of Medium-Sized Nitrogen Heterocycles through the Cyclization of Bromoallenes in the Presence of a Palladium(0) Catalyst and an Alcohol (pages 1749–1753)

      Hiroaki Ohno, Hisao Hamaguchi, Miyo Ohata and Tetsuaki Tanaka

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250589

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      A highly regio- and stereoselective synthesis of medium-sized nitrogen heterocycles has been developed (see scheme), based on the discovery that bromoallenes can act as an allyl dication equivalent in the presence of a palladium(0) catalyst and an alcohol. The intramolecular nucleophilic attack takes place exclusively at the central carbon atom of the allene moiety.

    19. The Second Total Synthesis of Diazonamide A (pages 1753–1758)

      K. C. Nicolaou, Paraselli Bheema Rao, Junliang Hao, Mali Venkat Reddy, Gerasimos Rassias, Xianhai Huang, David Y.-K. Chen and Scott A. Snyder

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200351112

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      The uniquely woven, highly strained molecular architecture and the potent antitumor activity of diazonamide A (1) make this natural product an attractive synthetic target. The key steps in this total synthesis of 1 include a novel SmI2-induced ring-closing cascade sequence and an unusual oxidation of an indoline to an oxindole in the presence of Pd(OH)2/C.

    20. First Evidence of a Single-Ion Electron Trap at the Surface of an Ionic Oxide (pages 1759–1761)

      Mario Chiesa, Maria Cristina Paganini, Elio Giamello, Cristiana Di Valentin and Gianfranco Pacchioni

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250811

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      A single electron can be trapped by a triply coordinated single cation at a magnesium oxide surface (see picture). The resulting center, denoted MgOcorner(H+/e), is a member of a new family of surface color centers and represents a significant advance for the concept of electron-trapping sites in solids.

    21. Resurrecting the Cornforth Model for Carbonyl Addition: Studies on the Origin of 1,2-Asymmetric Induction in Enolate Additions to Heteroatom-Substituted Aldehydes (pages 1761–1765)

      David A. Evans, Sarah J. Siska and Victor J. Cee

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200350979

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      Further experimental support for the Cornforth model is obtained from a systematic study of aldol reactions between methyl-substituted E and Z enolates and α-oxygen-substituted aldehydes. The observed dependence of diastereofacial selectivity on enolate configuration in this case is more consistent with the Cornforth model than with the the polar Felkin–Anh model (see scheme; X=OR, NR2, Cl).

    22. Sequence-Selective Molecular Recognition between β Sheets (pages 1765–1768)

      James S. Nowick and De Michael Chung

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200250750

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      Molecular recognition between peptide β sheets is sequence selective! By simply controlling the placement of two threonine (Thr) or valine (Val) residues, peptides that preferentially form either homodimers or heterodimers with about tenfold selectivity can be generated. The picture shows the structure of a Thr–Val⋅Val–Thr heterodimer.

    23. Preview: Angew. Chem. Int. Ed. 15/2003 (page 1773)

      Version of Record online: 16 APR 2003 | DOI: 10.1002/anie.200390384

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