Angewandte Chemie International Edition in English

Cover image for Vol. 34 Issue 4

March 7, 1995

Volume 34, Issue 4

Pages 371–497

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 4/1995)

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503691

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      The cover picture shows the space-filling model of an inorganic crown ether compound with an encapsulated sodium ion. The crown consists of six FeIII ions (virtually hidden) and the O atoms (orange) of six μ-MeO ligands (carbon atoms depicted in white). The Fe centers form an almost regular hexagon; their coordination spheres are completed by six additional bridging MeO ligands, which are also coordinated to the Na ion (yellow), and by six chelating dibenzoylmethanido ligands. More about this complex ion, which is interesting inter alia with regard to the course of the hydrolysis of iron(III) salts and the synthesis of models for the mineral core in ferritin, is reported by S. J. Lippard et al. on pages 467 ff.

  1. Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Vitamin B12: How the Problem of Its Biosynthesis Was Solved (pages 383–411)

      Francis Blanche, Beatrice Cameron, Dr. Joel Crouzet, Dr. Laurent Debussche, Denis Thibaut, Dr. Marc Vuilhorgne, Dr. Finian J. Leeper and Prof. Sir Alan R. Battersby

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199503831

      To discover how the complex molecule vitamin B12 (shown on the right) was formed in living systems was one of the greatest challenges in bioorganic chemistry. Since its structure determination and total synthesis, vitamin B12 has held a special fascination for chemists. But the tremendous achievement chronicled here is also of broader interest as an example of the productive interplay of modern methods in biology and chemistry.

    2. Enzymes in Organic Synthesis: Application to the Problems of Carbohydrate Recognition (Part 1) (pages 412–432)

      Prof. Dr. Chi-Huey Wong, Dr. Randall L. Halcomb, Prof. Dr. Yoshitaka Ichikawa and Dr. Tetsuya Kajimoto

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504121

      Enzymes, a tool of the preparative chemist. The use in synthesis of enzymes such as the aldolases covered here can no longer be overlooked, particularly in the field of carbohydrate chemistry. Since, for instance, the saccharides that are found on the surface of cells are information carriers on the molecular level and play a significant role in intercellular communication as well as the processes involved in infection, these processes can only be deliberately influenced if the relevant carbohydrates and carbohydrate analogs can be prepared stereoselectively in good yields and in sufficient quantities for pharmaceutical applications. Enzymatic syntheses fulfill these criteria in an elegant way.

  2. Highlights

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Asymmetric Alkylation of Amide Enolates with Pseudoephedrine and Ephedrine as Chiral Auxiliaries—Unexpected Influence of Additives? (pages 433–435)

      Dr. Karola Rück

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504331

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      The self-assembly of enolates can be controlled by the addition of nonstoichiometric amounts of metal salts. New findings on the structure-reactivity relationship of enolates and chemo-, regio-, and diasteroselectivities in their reactions with electrophiles are discussed. This article was prompted by a recent report by Myers et al. on a new method for the alkylation of amide enolates with pseudoephedrine as a chiral auxiliary [Eq. (a)].

    2. Phosphaalkyne Cyclooligomers: From Dimers to Hexamers—First Steps on the Way to Phosphorus–Carbon Cage Compounds (pages 436–438)

      Dr. Rainer Streubel

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504361

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      Following the early successes of the di- and trimerization of 1 to give 2 and 3, respectively, the tetraphosphabarrelene 4 and the hexaphospha-p-[32,56]octahedrane 5 were synthesized recently. These and other more recent advancements in the field of P[BOND]C cage compounds demonstrate once again the synthetic potential of tert-butylphosphaacetylene, which was prepared for the first time by Becker et al. in 1981.

  3. Communications

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. The Consequences of an Electrostatic “Forced Marriage” between Two Electron-Rich Particles: Strained Ion Pairs (pages 439–441)

      Prof. Dr. Robert Weiss, Dipl.-Chem. Thomas Brenner, Dr. Frank Hampel and Dr. Alexander Wolski

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504391

      Because of the extraordinary electronic situation in tris(dimethylamino)cyclopropenylium chloride 1, a salt with an electron-rich cation and anion, the “naked” CI ions in 1 show a very high readiness to coordinate to acceptors. Thus, stable adducts with hydrogen bonds are formed from 1 and carboxylic acids or phenol derivatives.

    2. Stable 1 : 1 Adducts from Iodoacetylenes and Iodide Ions: Ion Pair Strain as an Additional Driving Force? (pages 441–443)

      Prof. Dr. Robert Weiss, Dipl.-Chem. Michael Rechinger, Dr. Frank Hampel and Dr. Alexander Wolski

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504411

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      A hypervalent, one-dimensional polymer with interlocking zigzag chains (shown on the right) is obtained in the reaction of diiodoacetylene with tris(dimethylamino)cyclopropenylium iodide. The formation of the first stable 1:1 adduct from I ions and a compound with Csp-bonded I centers is attributed to strong n [RIGHTWARDS ARROW] σ* interactions.

    3. Tris(dimethylamino)sulfoniumcyclopentadienide [TAS]+[C5H5] and Tris(dimethylamino)-sulfoniumpyrrolide [TAS]+[C4H4N]: Two Isostructural Salts with “Naked” Anions A and the “Inverse” Sandwich-Cations [{(Me2N)3S}2A]+ (A = C5Hmath image, C4H4N) (pages 443–446)

      Jens Wessel, Prof. Dr. Ulrich Behrens, Enno Lork and Prof. Dr. Rüdiger Mews

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504431

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      By conversion of the sulfonium salt 1 with the cyclopentadiene 2 the readily soluble salt 3 is obtained in high yield. “Naked” Cp ions and cations of [{(Me2N)3S}2Cp]+ with an inverse sandwich structure are present in crystals of 3. A variety of silylated N-heterocycles react with 1 in a similar way to form the corresponding salts. These salts are interesting inter alia for their potential use as building blocks in synthesis.

    4. Light-Switchable Catalysis in Synthetic Receptors (pages 446–448)

      Dr. Frank Würthner and Prof. Julius Rebek Jr.

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504461

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      Catalysis by flicking a “light switch” is possible with an azobenzene-based template. When the E isomer of the template is irradiated with light of wavelength 366 nm, the isomeric composition is shifted in favor of the catalytically active Z isomer, and the reaction rate for amide bond formation between modified adenine units is increased by a factor of 10. The light-induced activation of the template is depicted schematically on the right.

    5. Discrimination between Enantiotopic Groups in a Diels–Alder Reaction (pages 448–450)

      Prof. Dr. Peter G. Jones, Dipl.-Chem. Hilmar Weinmann and Prof. Dr. Ekkehard Winterfeldt

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504481

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      The steric demand of an oxygen atom is less than that of a CH2 group in the kinetic resolution of chiral dienophiles with the enantiomerically pure dienes 1 and ent-1 (R = OCH3). This realization led to the first differentiation between enantiotopic double bonds in a Diels–Alder reaction for the spirolactone 2 and spiroether 3.

    6. Discrete Crown-Shaped Te8 Rings in Cs3 Te22 (pages 450–451)

      Prof. Dr. William S. Sheldrick and Dipl.-Chem. Michael Wachhold

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504501

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      Structural features of the heavier and lighter homologues of tellurium are embodied in the two partial structures of Cs3Te22: crown-shaped Te8 rings, which are stabilized in the coordination sphere of a cesium cation (shown on the right), are similar to analogous S8 and Se8 rings, whereas the layer anions math image[Te4Temath image] may be derived from the α-polonium structure. Cs3Te22 was prepared from Cs2CO3 and As2Te3 in superheated methanol.

    7. A Novel Intramolecular Heck Reaction: Synthesis of a Cholesterol - Baccatin III Hybrid (pages 452–455)

      Dr. John J. Masters, David K. Jung, Prof. Samuel J. Danishefsky, Dr. Lawrence B. Snyder, Dr. Tae Kyo Park, Dr. Richard C. A. Issacs, Dr. Cheryl A. Alaimo and Dr. Wendy B. Young

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504521

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      Despite strong repulsion between the methyl groups, the intramolecular Heck reaction of cyclohexenyl trifluoromethanesulfonate 1, available from 5-α-cholestan-3-one, proceeds in 50% yield. The product of the Heck reaction can be converted in a few subsequent steps into the cholesterol-baccatin III hybrid 2.

    8. Enantioselective Synthesis of β-Amino Acids: TMS-SAMP as a Chiral Ammonia Equivalent for the Aza Analogous Michael Addition to α,β-Unsaturated Esters (pages 455–457)

      Prof. Dieter Enders, Dr. Heiner Wahl and Dr. Wolfgang Bettray

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504551

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      The N-silylated chiral amines TMS-SAMP and TMS-RAMP can be employed for stereoselective C[BOND]N bond formation with enantiomeric excesses of 90-80%. In these reactions, the corresponding hydrazinoesters are formed initially, which are subsequently cleaved hydrogenolytically to give the desired β-amino acids 1. R = alkyl, R′ = Me, tBu.

    9. Sulfoxide-Stabilized Giant Palladium Clusters in Catalyzed Oxidations (pages 457–460)

      Rolf A. T. M. van Benthem, Dr. Henk Hiemstra, Prof. Dr. Piet W. N. M. van Leeuwen, Prof. John W. Geus and Prof. Dr. W. Nico Speckamp

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504571

      Transmission electron microscopy has been used to characterize the large solvent-stabilized palladium clusters with uniform size distribution that are formed in homogeneous PdII-catalyzed oxidations in dimethyl sulfoxide.

    10. Synthesis, Structure, and Reactivity of an Imido- and an Oxo(imido)phosphorane R[BOND]P([DOUBLE BOND]X)[DOUBLE BOND]NR (X[DOUBLE BOND]NH, O; R = tBu3C6H2 (pages 460–462)

      Dipl.-Chem. Martin Larbig, Dr. Martin Nieger, Dr. Volker von der Gönna, Dr. Alexander V. Ruban and Prof. Dr. Edgar Niecke

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504601

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      A high synthetic potential is promised by imido(imino)phosphorane 2 accessible by N2 elimination from the azidophosphane 1. In 2, as in the isoelectronic oxygen derivative 3, the phosphorus atom is in a trigonal-planar environment. Ar = 2,4,6-tBu3C6H2.

    11. Chiral Phosphanodihydrooxazoles in Asymmetric Catalysis: Tungsten-Catalyzed Allylic Substitution (pages 462–464)

      Dr. Guy C. Lloyd-Jones and Prof. Dr. Andreas Pfaltz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504621

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      Enantiomeric excesses up to 96% have been obtained in allylic alkylations of 3-aryl-2-propenyl phosphates 2 to give 3 with CH(CO2Me)math image as nucleophile Nu by using a new tungsten catalyst derived from the phosphanodihydrooxazole complex 1 (X = CH3CN). The regioselectivity is opposite to that of analogous Pd-catalyzed reactions.

    12. Bis(dicyanomethylene) and Bis(cyanoimino) Derivatives of Indigo and Thioindigo (pages 464–467)

      Prof. Dr. Rudolf Gompper, Dr. Karsten Hartmann, Dr. Robert Kellner and Dr. Kurt Polborn

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504641

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      Indigo in which [DOUBLE BOND]O is replaced by [DOUBLE BOND]C(CN)2 (1) or [DOUBLE BOND]N[BOND]CN was prepared for the first time. Both compounds and their derivatives absorb in the near-IR at considerably longer wavelengths than indigo. Attempts to synthesize the analogous thioindigo derivatives led to compounds 2-4 (X = S, SO2) by reaction sequences that were sometimes unexpected.

    13. A Cyclic Hexairon(III) Complex with an Octahedrally Coordinated Sodium Ion at the Center, an Example of the [12]Metallacrown-6 Structure Type (pages 467–469)

      Dr. Andrea Caneschi, Andrea Cornia and Prof. Stephen J. Lippard

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504671

      A crown composed purely of inorganic components forms the core of complex cation 1. Interest in this polyiron ion is based on its potential relevance to intermediates in the formation of the ferritin core and the hydrolytic polymerization of FeIII salts. The crown structure is supported by the inclusion of a sodium ion within the Fe6O6 ring.

      • equation image
    14. Modified Triple Resonance NMR Experiments with Optimized Sensitivity for Rapidly Exchanging Protons (pages 469–471)

      Dipl.-Chem. Wolfgang Jahnke and Prof. Dr. Horst Kessler

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504691

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      Fast exchange with surrounding water protons need not attenuate 1H NMR signals of proteins in solution. A modified pulse sequence has been developed to increase the signal intensity of the amide protons; on the right the improvement in sensitivity (a [RIGHTWARDS ARROW] c) is shown for a selected residue in a protein. This new technique should aid elucidation of protein structures in solution.

    15. The Arndt–Eistert Reaction in Peptide Chemistry: A Facile Access to Homopeptides (pages 471–472)

      Dr. Joachim Podlech and Prof. Dr. Dieter Seebach

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504711

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      By combination of an Arndt-Eistert reaction sequence and a peptide coupling, amino acids and peptides can be coupled with a second amino acid or a second peptide to give homopeptides, for example of type 1. This method has been employed to synthesize up to homohexapeptides.

    16. Rapid Hydrolysis of RNA with a CuII Complex (pages 472–474)

      Barry Linkletter and Prof. Jik Chin

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504721

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      The methyl groups in copper complex 1 not only prevent dimerization but also activate the complex for RNA hydrolysis. The half-life for the hydrolysis of ApA (0.5 mM) promoted by 1 is only 3 min. Thus 1 is currently the most effective transition metal complex for hydrolyzing RNA.

    17. Photo Electron Transfer Induced Macrocyclization of N-Phthaloyl-ω-aminocarboxylic Acids (pages 474–476)

      Prof. Dr. Axel G. Griesbeck, Dipl.-Chem. Andreas Henz, Dr. Karl Peters, Dr. Eva-Maria Peters and Prof. Dr. Hans Georg von Schnering

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504741

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      Macrocycles of type 2 with up to 26 ring atoms (n = 22) are available in very good yields by photo electron transfer (PET) initiated decarboxylation of the anions of N-phthaloyl-ω-aminocarboxylic acids 1. The electron transfer is favored as a result of intramolecular K+-mediated chelation; however, it can also occur efficiently over larger donor-acceptor distances.

    18. Computational Evidence for the Existence of CuIII Intermediates in Addition and Substitution Reactions with Dialkylcuprates (pages 476–478)

      Dr. Andrea E. Dorigo, Diplom-Chem. Jutta Wanner and Prof. Dr. Paul von Ragué Schleyer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504761

      When the copper center is stabilized by donor ligands such as H2O and NH3, trialkylcopper compounds correspond to energy minima at all levels of theory used in the calculations (MP2, SCRF, BLYP). These results support proposals that such species are intermediates in cuprate addition and substitution reactions and at the same time suggest that descriptions of trialkylcopper systems as CuII rather than CuIII complexes may be more appropriate.

    19. The First Unambiguous Characterization of a Neutral Phosphorus Ylide–Lithium Complex: Isolation, Structure, and Ab Initio Investigations of [(PhCH2)2NLi · CH2PPh3]2 (pages 478–481)

      Dr. David R. Armstrong, Dr. Matthew G. Davidson and Dr. David Moncrieff

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504781

      A four-membered ring of two lithium and two nitrogen atoms is in the central unit of the dimer in the title (1), a complex between an alkali metal and a neutral phosphorus ylide. Surprisingly, this is the first time that such a model complex for the generation of ylides from phosphonium salts and alkali metal bases has been characterized in the solid state. The structure in solution was also determined, and the complexation energies for this and other model complexes were estimated by ab initio calculations.

      • equation image
    20. C60H60 and C54H48: Silver Ion Extraction with New Concave Hydrocarbons (pages 481–484)

      Dr. Jens Gross, Dipl.-Chem. Gabriele Harder, Prof. Dr. Fritz Vögtle, Dr. Holger Stephan and Prof. Dr. Karsten Gloe

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504811

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      The intramolecular cavity of the spherical, concave hydrocarbons C60H601 and C54H482 is accessible to guest molecules through openings on their surfaces. The new carbocycles can be used to extract silver ions from the aqueous phase; 1 shows high selectivity and the best extraction properties of the known complex-forming hydrocarbons.

    21. Tetraphosphatricyclo[,5]octadienes; New Phosphaalkyne Cyclotetramers Derived from λ3σ2-Diphosphetes (pages 484–487)

      Dr. Bernhard Geissler, Dr. Stefan Barth, Dr. Uwe Bergsträsser, Dr. Michael Slany, Julie Durkin, Dr. Peter B. Hitchcock, Dipl.-Chem. Matthias Hofmann, Prof. Dr. Paul Binger, Prof. Dr. John F. Nixon, Prof. Dr. Paul von Ragué Schleyer and Prof. Dr. Manfred Regitz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504841

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      Two new tetrameric phosphaalkynes, the isomers 1 and 3, have been synthesized. The cyclotetramer 1 with a “central” P4 unit forms in high yield by the demetalation of the zirconium compound 2 with [(Ph3P)2NiCl2]. The isomer 3, which contains two P[BOND]C double bonds, is obtained as a by-product in the reaction of 2 with hexachloroethane; the major product is the tetraphosphacubane 4.

    22. Crystal Structure of the Dimeric (4-tert-Butylthiazolato)(glyme)lithium: Carbene Character of a Formyl Anion Equivalent (pages 487–489)

      Prof. Dr. Gernot Boche, Dipl.-Chem. Christof Hilf, Dr. Klaus Harms, Michael Marsch and Dr. John C. W. Lohrenz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504871

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      For the first time the carbene character of a formyl anion equivalent can be demonstrated in the crystal structure of the title compound 1. A comparison of the structures of thiazole, the stable nucleophilic carbene 2 (both accessible experimentally), and LiCH[DOUBLE BOND]O (calculated) leads to this result. Furthermore, 1 is yet another example of complexes of nucleophilic carbenes with Lewis acids, which have aroused great interest lately.

    23. Common Origin of Enthalpic and Entropic Substituent Effects in Reactions of Benzhydryl Cations with Nucleophiles (pages 490–492)

      Dr. Matthias Patz, Prof. Dr. Herbert Mayr, Dr. Jörg Bartl and Prof. Dr. Steen Steenken

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504901

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      As long as an enthalpic barrier is present, a decrease in the electron-releasing ability of X and Y causes an increase in the reaction rates of reaction (a) due to the lowering of the activation enthalpy, while the activation entropy remains constant. When the enthalpic barrier disappears, further decrease in the electron-releasing ability of X and Y is associated with an increase in reactivity caused by an increase in the activation entropy.

    24. The First Distibabutadiene: Synthesis and Structure of trans-1,4-Bis(trimethylsiloxy)-1,4-bis(2,4,6-tri-tert-butylphenyl)-2,3-distibabutadiene (pages 492–493)

      Dr. Peter B. Hitchcock, Dr. Cameron Jones and Prof. John F. Nixon

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199504921

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      A λ32 Sb[BOND]C double bond that is not part of a cyclic electron system is present in the distibabutadiene 1, which is formed in the reaction of (2,4,6-C6H2tBu3)COCl with Li[Sb(SiMe3)2(dme)]. The X-ray crystal structure analysis of 1 indicates a degree of double-bond delocalization that, in addition to steric bulk, stabilizes this unusual molecule.

  4. Book Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews