Angewandte Chemie International Edition

Cover image for Vol. 42 Issue 41

October 27, 2003

Volume 42, Issue 41

Pages 4979–5101

    1. Cover Picture: The Ethylene Polymerization with Ziegler Catalysts: Fifty Years after the Discovery (Angew. Chem. Int. Ed. 41/2003) (page 4979)

      Ludwig L. Böhm

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200390602

      Fifty years ago Karl Ziegler and co-workers discovered the now-famous process for the catalytic production of polyethylene at moderate temperatures and pressures. The cover of the patent gives November 18, 1953 as the priority date. Today, 50 years on, as a result of highly active catalysts and a detailed understanding of the system on all scales, it is still an extremely viable process. In his Review on page 5010 ff. L. L. Böhm describes the current industrial process based on Ziegler catalysts.

    2. Ruthenium-Catalyzed Cyclizations: More than Just Olefin Metathesis! (pages 4996–4999)

      Bernd Schmidt

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200301688

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      From unexpected side products to new catalytic cyclizations: Numerous ruthenium-catalyzed cyclization reactions that probably proceed via five-membered ruthenium metallacycles and do not involve olefin metathesis have been described recently. The border between metathesis and nonmetathesis cyclization pathways is not always clearly defined. This phenomenon can lead to the discovery of new ruthenium-catalyzed reactions (see scheme; X=CR2, NR).

    3. Fifty Years of Ziegler Catalysts: Consequences and Development of an Invention (pages 5000–5008)

      Günther Wilke

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200330056

      In October, 1953 an experiment was carried out in the Max Planck Institut für Kohlenforschung in Mülheim an der Ruhr, that even today has a huge influence on the chemical industry: the catalytic polymerization of ethylene under normal pressure carried out with what at the time was known as the Mülheim mixed catalyst. The story of what is know known as the Ziegler catalyst reveals its discovery to be the result of the meticulous analysis of apparently failed experiments.

    4. The Ethylene Polymerization with Ziegler Catalysts: Fifty Years after the Discovery (pages 5010–5030)

      Ludwig L. Böhm

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200300580

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      Happy birthday! 50 years after the discovery of the catalytic polymerization of ethylene with Ziegler catalysts (see scheme) this process is still a vital, modern, industrial process. Based on high-performance catalysts and a broad process knowledge, products with excellent combinations of properties for a wide-range of applications can be produced in an economical environmentally friendly and resources saving way.

    5. Reversible Insulator-to-Metal Transition in p+-Type Mesoporous Silicon Induced by the Adsorption of Ammonia (pages 5032–5035)

      Mario Chiesa, Giampiero Amato, Luca Boarino, Edoardo Garrone, Francesco Geobaldo and Elio Giamello

      Version of Record online: 25 AUG 2003 | DOI: 10.1002/anie.200352114

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      Gas works wonders! Conduction-band electrons can be generated in p+-type mesoporous crystalline silicon through the adsorption of ammonia (see scheme). Free-carrier concentration increases with increasing NH3 adsorption to a critical value, where a reversible insulator-to-metal transition occurs.

    6. Colloidal Two-Dimensional Systems: CdSe Quantum Shells and Wells (pages 5035–5039)

      David Battaglia, Jack J. Li, Yunjun Wang and Xiaogang Peng

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200352120

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      Thin CdSe layers (“quantum shells”) were epitaxially grown onto CdS nanocrystal templates. Their optical properties are dominated by the shell thickness despite the different bandgap and size of the templates. The emission of the CdSe quantum shells, which can be tuned by varying the shell thickness, ranges from 520 to 650 nm (see Figure), and the emission quantum yield can be increased to over 40 % by coating the quantum shells with epitaxially grown CdS thin layers (CdSe colloidal “quantum wells”).

    7. Trapping Cations in Specific Positions in Tuneable “Artificial Cell” Channels: New Nanochemistry Perspectives (pages 5039–5044)

      Achim Müller, Samar K. Das, Sergei Talismanov, Soumyajit Roy, Eike Beckmann, Hartmut Bögge, Marc Schmidtmann, Alice Merca, Alois Berkle, Lionel Allouche, Yunshan Zhou and Lijuan Zhang

      Version of Record online: 8 OCT 2003 | DOI: 10.1002/anie.200352358

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      A decision-making capsule! Where cation trafficking comes to a halt is predetermined, with the process corresponding to a “nano-ion chromatograph” in action: starting from pores the route may end in a finely sculpturable interior of a stable, soluble spherical capsule but in many cases it ends in between in channels that exhibit a variety of cation-capturing functionalities at different positions (one of the twenty channels is shown with the residing cations).

    8. On the Mechanism of the Anionic Oxy-Cope Rearrangement of trans-1,2-Dialkenylcyclobutanols (pages 5044–5047)

      Philippe Maurin, Se-Ho Kim, Sung Yun Cho and Jin Kun Cha

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200350988

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      A concerted mechanism involving a chairlike transition state (see scheme) and no appreciable loss of enantiopurity was concluded for the anionic oxy-Cope rearrangement of sterically unencumbered trans-1,2-dialkenylcyclobutanols from a study employing nonracemic substrates containing vinyl and propenyl groups with evaluation of the enantio- and diastereofacial selectivity.

    9. Recovering Methane from Solid Methane Hydrate with Carbon Dioxide (pages 5048–5051)

      Huen Lee, Yongwon Seo, Yu-Taek Seo, Igor L. Moudrakovski and John A. Ripmeester

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200351489

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      CO2in, CH4out! From NMR spectroscopic measurements of composition and kinetics, it can be shown that the recovery of methane from methane hydrate is possible through its reaction with CO2 (see diagram), even though the yield is less than that expected from kinetic and thermodynamic arguments.

    10. A General Method for the Direct α-Arylation of Nitriles with Aryl Chlorides (pages 5051–5053)

      Jingsong You and John G. Verkade

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200351954

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      The long-standing challenge of developing a general method for the title methodology is met for a broad range of aryl chlorides through the use of bicyclic P(iBuNCH2CH2)3N (1) as a bulky electron-rich ligand for palladium (see scheme, dba=dibenzylideneacetone).

    11. A Highly Active and Selective Catalyst System for the Baylis–Hillman Reaction (pages 5054–5056)

      Jingsong You, Juhua Xu and John G. Verkade

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200352233

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      A key role for sulfur and the potential for Nax[RIGHTWARDS ARROW]P intrabridgehead interactions are invoked to explain the impressive effect of the cocatalyst (shown in color) in the TiCl4-mediated Baylis–Hillman reaction [Eq. (1)]. Even sterically hindered and electronically deactivated aldehydes such as o-anisaldehyde can be coupled under these conditions. EWG=electron-withdrawing group, RT=room temperature.

    12. Enantioselective Alkynylation of Aromatic Ketones Catalyzed by Chiral Camphorsulfonamide Ligands (pages 5057–5058)

      Gui Lu, Xingshu Li, Xian Jia, Wing Lai Chan and Albert S. C. Chan

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200352013

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      The smooth addition of phenylacetylene to aromatic ketones in the presence of catalytic amounts of Cu(OTf)2 and camphorsulfonamide provides the corresponding tertiary propargylic alcohols in high yields and with up to 97 % ee. This reaction represents a highly enantioselective catalytic addition of dialkynyl zinc reagents to simple ketones.

    13. A Modular Approach to Oxoindolizino Quinolines: Efficient Synthesis of Mappicine Ketone (Nothapodytine B) (pages 5059–5061)

      Gajendra B. Raolji, Stéphanie Garçon, Andrew E. Greene and Alice Kanazawa

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200352094

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      A general route to oxoindolizino quinolines, such as nothapodytine A, mappicine, camptothecin, and several chemotherapeutic derivatives, is illustrated by the synthesis of the antiviral natural product from Nothapodytes foetida, mappicine ketone (R1=R4=H, R2=CH3, R3=COC2H5). A wide range of new camptothecinoids should now be readily available for biological testing.

    14. Enantioselective Radical Addition to N-Acyl Hydrazones Mediated by Chiral Lewis Acids (pages 5061–5063)

      Gregory K. Friestad, Yuehai Shen and Erik L. Ruggles

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200352104

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      A radical concept: In the presence of chiral CuII–bisoxazoline complexes, the addition of alkyl radicals to achiral N-acyl hydrazones, which have a two-point-binding motif, proceeded with high enantioselectivity. Evidence of catalyst turnover was demonstrated, providing the first example of asymmetric catalysis in radical additions to C[DOUBLE BOND]N bonds.

    15. The Dual Roles of Oxodiperoxovanadate Both as a Nucleophile and an Oxidant in the Green Oxidation of Benzyl Alcohols or Benzyl Halides to Aldehydes and Ketones (pages 5063–5066)

      Chunbao Li, Pengwu Zheng, Jie Li, Hang Zhang, Yi Cui, Qiyun Shao, Xiujie Ji, Jian Zhang, Pengying Zhao and Yanli Xu

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200351902

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      One catalyst, two roles: VO(O2)2 reacts as a nucleophilic oxidant under acidic conditions towards benzyl alcohols. Altogether 15 alcohols have been oxidized, in the absence of organic solvent, in excellent yields. Benzyl halides are also oxidized by H2O2 in water catalyzed by oxodiperoxovanadate and a phase transfer catalyst into aromatic aldehydes and ketones (see scheme). This reaction is the first green oxidation of benzyl halides.

    16. [Cp*(η2-bipy)(MeCN)RuII][PF6] Catalysts for Regioselective Allylic Substitution and Characterization of Dicationic [Cp*(η2-bipy)(η3-allyl)RuIV][PF6]2 Intermediates (pages 5066–5068)

      Mbaye D. Mbaye, Bernard Demerseman, Jean-Luc Renaud, Loïc Toupet and Christian Bruneau

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200352257

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      The coordination of a 2,2′-bipyridyl derivative to a (C5Me5)RuII fragment provides both a facile route to unprecedented dicationic (allyl)RuIV complexes (see picture) and new highly efficient catalysts for the regioselective allylic substitution from unsymmetrical allylic carbonates.

    17. Development of a Novel Sugar Linkage: 6,6′-Ether-Connected Sugars (pages 5069–5071)

      Hideyo Takahashi, Toshimitsu Fukuda, Haruhiko Mitsuzuka, Rie Namme, Hidetoshi Miyamoto, Yasufumi Ohkura and Shiro Ikegami

      Version of Record online: 6 OCT 2003 | DOI: 10.1002/anie.200352388

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      Unusual sugar dimers: The synthesis of 6,6′-ether-connected pyranoses by an acetalization–reduction procedure is described (see scheme). Structure–activity-relationship studies of these novel carbohydrate dimers suggested that the natural product coyolosa, which has been shown to have a significant effect on fasting blood-glucose levels, may have a different structure from the one previously reported.

    18. Site Titration with Organic Bases During Catalysis: Selectivity Modifier and Structural Probe in Methanol Oxidation on Keggin Clusters (pages 5072–5075)

      Haichao Liu, Nader Bayat and Enrique Iglesia

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200352393

      The selective and permanent titration of protons with organic bases (2,6-di-tert-butylpyridine or pyridine) provides an accurate measure of the dispersion of Keggin structures during catalytic oxidation of methanol. Titration allows the systematic control of the redox and acid properties of H3+nPVnMo12−nO40 (n=0–4) Keggin clusters and leads to unprecedented selectivity in the formation of dimethoxymethane (>80 %) and high yields.

    19. Homogeneous Ethylene-Polymerization Catalysts Based on Alkyl Cations of the Rare-Earth Metals: Are Dicationic Mono(alkyl) Complexes the Active Species? (pages 5075–5079)

      Stefan Arndt, Thomas P. Spaniol and Jun Okuda

      Version of Record online: 8 OCT 2003 | DOI: 10.1002/anie.200352532

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      Easily accessible, the tris(alkyl) complexes of rare-earth elements [Ln(CH2SiMe3)3(thf)2] are activated by [NMe2HPh][B(C6F5)4] in the presence of AliBu3 to catalyze homogeneous ethylene polymerization. Model reactions show that the bis(alkyl) yttrium monocation is converted into the mono(alkyl) dication (see picture), which appears to be the active species in ethylene polymerization.

    20. Ligands for Palladium-Catalyzed Cross-Couplings of Alkyl Halides: Use of an Alkyldiaminophosphane Expands the Scope of the Stille Reaction (pages 5079–5082)

      Haifeng Tang, Karsten Menzel and Gregory C. Fu

      Version of Record online: 14 OCT 2003 | DOI: 10.1002/anie.200352668

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      Alkyldiaminophosphanes (PR(NR′2)2) are a new class of ligands for palladium-catalyzed cross-couplings of alkyl halides (see scheme). In comparison with trialkylphosphanes, alkyldiaminophosphanes furnish more versatile catalysts for Stille reactions of alkyl bromides and achieve efficient couplings with both vinyl and aryl stannanes. Furthermore, Pd/PR(NR′2)2 provides the first method for accomplishing Stille cross-couplings of simple alkyl iodides that bear β-hydrogen atoms.

    21. Elemental Gallium as a Source of Subvalent Gallium Units in Gallium–Rhodium Clusters (pages 5083–5086)

      Manfred Scheer, Martin Kaupp, Alexander V. Virovets and Sergei N. Konchenko

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200351226

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      Mild reduction with metals: Elemental gallium is used as mild reducing agent for transition-metal halides to generate subvalent GaCl ligands in novel clusters. In the reaction of Ga with [{Cp′′RhCl2}] (Cp′′=η5-1,3-C5H3tBu2), clusters with GaCl ligands and with unprecedented two-coordinate Ga centers in a multicenter–multiple-bonding interaction between two rhodium centers are formed (see picture).

    22. A Gas-Phase Reaction as a Functional Model for the Activation of Carbon Dioxide by Carbonic Anhydrase (pages 5087–5090)

      Detlef Schröder, Helmut Schwarz, Stephan Schenk and Ernst Anders

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200351440

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      Masses of evidence: Mass spectrometry combined with 18O labeling reveals that the imidazole and pyridine complexes [LnZnOH]+ (n=1, 2) are capable of activating carbon dioxide, under thermal conditions. These gas-phase reactions thus provide a simple mimic for the function of the active site in carbonic anhydrase.

    23. Microkinetic Videomicroscopic Analysis of Olefin Polymerization with a Supported Metallocene Catalyst (pages 5090–5093)

      Stefan Knoke, Daniela Ferrari, Bernd Tesche and Gerhard Fink

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200351582

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      Picture this: The simultaneous growth of many single grains of catalyst culminating in polymer particles can be observed by videomicroscopy, and single-grain kinetics can be studied. The gas-phase polymerization of ethylene on 40 particles was examined in an autoclave equipped with a glass window by automatic image processing. The picture shows the overlap of three different stages of the polymerization after 0 (blue), 60 (red), and 180 (yellow) minutes.

    24. Carbonylbiscaprolactam: A Versatile Reagent for Organic Synthesis and Isocyanate-Free Urethane Chemistry (pages 5094–5097)

      Steffen Maier, Ton Loontjens, Boudewijn Scholtens and Rolf Mülhaupt

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200351867

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      The power of the rings: The reactions of carbonylbiscaprolactam (CBC, 1) with amines and alcohols proceed either by ring elimination (RE) or by ring opening (RO). The conversion and selectivity of these reactions were optimized in studies with various hydroxy and amino compounds, catalysts, reaction temperatures, and ratios of 1/nucleophile.

    25. Preview: Angew. Chem. Int. Ed. 41/2003 (page 5101)

      Version of Record online: 22 OCT 2003 | DOI: 10.1002/anie.200390605