Angewandte Chemie International Edition in English

Cover image for Vol. 35 Issue 9

May 20, 1996

Volume 35, Issue 9

Pages 923–1027

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 9/1996)

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609211

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      The cover picture shows the ball-and-stick model of an α-silylated β-dibenzylamino ketone (color code: C = gray, O = red, N = blue, Si = green, and Br = claret), which is accessible in a straightforward manner from butanone and from which the corresponding amino ketone can be synthesized readily by racemization-free desilylation. This conversion can be achieved with a whole series of silylated precursors. Thus, roughly 80 years after the discovery of the aminomethylation of aldehydes and ketones by Carl Mannich, this procedure provides the first access to a practical enantioselective Mannich reaction. More about this novel synthetic route to β-amino ketones, which are of great preparative interest, is reported by D. Enders et al. on p. 981 ff.

  1. Reviews

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. The Mechanism of the Claisen Rearrangement: Déjà Vu All Over Again (pages 936–945)

      Prof. Bruce Ganem

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609361

      How can an enzyme accelerate a pericyclic reaction? The classical effects of solvents and catalysts, which were largely ignored by the chemical community, provide important information about the mechanism of the enzyme, and put the Claisen rearrangement in a new perspective. Nature, it seems, has been paying close attention to the chemical literature!

    2. Protonation of Unsaturated Hydrocarbon Ligands: Regioselectivity, Stereoselectivity, and Product Specificity (pages 946–967)

      Dr. Richard A. Henderson

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609461

      Counterintuitive product distribution results can be understood when the reaction mechanism is elucidated by kinetic analysis. Thus, the protonation of alkene complexes gives alkanes at low acid concentration and alkenes at high acid concentration, and this can be explained by pathways involving competitive protonation of the metal or the ligand. Mechanistic studies on the reactions of acids with complexes containing unsaturated hydrocarbon ligands show that the product selectivity need not be attributable to simple regioselective attack of the proton at the hydrocarbon. The ramifications of these mechanistic features on the control of the products of a reaction and their stereochemistry are discussed.

  2. Highlights

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Organometallic “Carbon Chains”: They Just Keep Getting Longer! (pages 969–971)

      Dr. Uwe H. F. Bunz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609691

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      Predominantly air- and moisture-stable carbyne derivatives such as 1 have been synthesized by Gladysz et al. Compound 1 contains the longest C[BOND]C chain in compounds of this type to date. The rhenium centers in 1 are electronically independent from each other, which, however, is not true for the shorter homologues.

    2. Recent Developments in the Enantioselective Syntheses of Cyclopropanes (pages 971–973)

      Prof. Dr. Hans-Ulrich Reissig

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609711

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      A new type of chiral vinylcarbene equivalent used by S. Hanessian et al. is the optically active chloroallylphosphonic acid amide 1. After deprotonation it adds to α,β-unsaturated carbonyl compounds 2 (R = H, Me) to yield the highly functionalized cyclopropane derivatives 3 with a high degree of enantiomeric purity. The substitution pattern of the cyclopropane derivatives predestines them to be starting materials for many syntheses.

  3. Communications

    1. Top of page
    2. Reviews
    3. Highlights
    4. Communications
    5. Book Reviews
    1. Prototype of an Optically Responsive Molecular Switch Based on Pseudorotaxane (pages 976–978)

      Dr. Masumi Asakawa, Dr. Sayeedha Iqbal, Prof. J. Fraser Stoddart and Dr. Nigel D. Tinker

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609761

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      A negative allosteric effect is observed in the [2]pseudorotaxane incorporating the 1,5-dioxynaphthalene derivative stoppered at one end by the [18]crown-6 macrocycle when it binds alkali metal cations. This effect can be exploited to elicit an optical response that can be monitored by UV spectroscopy. The principle is illustrated schematically below.

    2. Simple Molecular Machines: Chemically Driven Unthreading and Rethreading of a [2]Pseudorotaxane (pages 978–981)

      Dr. Roberto Ballardini, Prof. Vincenzo Balzani, Alberto Credi, Dr. Maria Teresa Gandolfi, Dr. Steven J. Langford, Dr. Stephan Menzer, Dr. Luca Prodi, Prof. J. Fraser Stoddart, Dr. Margherita Venturi and Dr. David J. Williams

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609781

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      The 2,7-dibenzyldiazoniapyrene dication 22+ is unthreaded from the pseudorotaxane 12+ by addition of the aliphatic amine A. Protonation of the amine disrupts the interactions between A and 22+ and thus rethreading of 22+ by 1,5-dinaphtho-[38]crown-10 (3) can occur, making the whole process reversible. The changes in the relative positions of the components can be monitored by absorption and luminescence spectroscopy.

    3. Efficient Regio- and Enantioselective Mannich Reactions (pages 981–984)

      Prof. Dr. Dieter Enders, Dr. David Ward, Dipl.-Chem. Johannes Adam and Dr. Gerhard Raabe

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609811

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      The readily accessible silyl ketone (S)-1 is an intermediate in the first practical, asymmetric Mannich reactions for the regio- and highly enantioselective α-aminomethylation of ketones. The synthetically and pharmaceutically valuable Mannich bases (R)-2 are obtained in excellent yields and high enantiomeric excesses. tHex = 1,1,2-trimethylpropyl.

    4. Hückel Arenes with Ten π Electrons: Cyclic Zintl Anions Simath image and Gemath image, Isosteric to Pmath image and Asmath image (pages 984–986)

      Prof. Dr. Hans Georg von Schnering, Dr. Urs Bolle, Dipl.-Ing. Jan Curda, Dr. Karl Peters, Dr. Wilder Carrillo-Cabrera, Dr. Mehmet Somer, Dipl.-Chem. Martin Schultheiss and Dr. Ulrich Wedig

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609841

      A new Zintl anion Xmath image (X = Si, Ge) appears in the compounds Ba4Li2Si6, B4Li2Ge6, and Ba10Ge7O3. Bonding within the anion and its interaction with the crystal field is described in terms of the electron localization function (ELF), which allows the visualization of covalent bonds, n electron pairs, and core shells. The existence of such cyclic anions indicates that in the solid-state structures of heavier Group 14 elements the formation of ten π electron Hückel arenes is preferred over the formation of discrete double bonds.

    5. Molecular, Shell-Like Dilithium (Silyl)phosphanediide and Dilithium (Silyl)arsanediide Aggregates with an [Li6O]4+ Core (pages 986–988)

      Priv.-Doz. Dr. Matthias Driess, Dr. Hans Pritzkow, Stefan Martin, Stefan Rell, Prof. Dr. Dieter Fenske and Gerhard Baum

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609861

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      Lithium-rich main group element clusters characterize the title compounds 1 and 2 (right: structure of 1 without silyl substituents; back = P,O, white = Li), which are obtained by lithiation of the appropriate primary silylphosphane and silylarsane, respectively, with two equivalents of nBuLi in the presence of Li2O. The frameworks of 1 and 2 are topologically best described as two interpenetrating shells of silylated P or As dianions and Li cations, with a formal charge of −4, which encapsulate a [Li6O]4+ octahedron.

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    6. Solid-State Coordination Chemistry: Hydrothermal Synthesis of Layered Vanadium Oxides with Interlayer Metal Coordination Complexes (pages 989–991)

      Dr. Yiping Zhang, Dr. Jeffrey R. D. DeBord, Prof. Charles J. O'Connor, Dr. Robert C. Haushalter, Prof. Abraham Clearfield and Prof. Jon Zubieta

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609891

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      A new class of solid-state materials are the hydrothermally synthesized compounds (L2M)y[VOx] (L = bidentate amine, M = Cu or Zn), which combine mixed-valence vanadium oxide layers with interlamellar coordination complexes. A section of the crystal structure of one example of these compounds with M = Cu and L = ethylenediamine is shown on the right.

    7. [Os10(CO)24{Au(PPh2R)}4], A Tubular Heterobimetallic Carbonyl–Osmium Cluster (pages 992–993)

      Zareen Akhter, Dr. Scott L. Ingham, Prof. the Lord Jack Lewis and Dr. Paul R. Raithby

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609921

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      Weak Os[BOND]Os interactions are a feature of these open tubular clusters, which have not been previously observed in high nuclearity Os cluster compounds. The bond lengths have been determined by X-ray analysis for the case in which R = Me (see picture). These clusters were synthesized by reduction of the dianion [Os10(CO)26]2− and subsequent addition of the cation [Au(PPh2R)]+.

    8. Reactions of a Triosmium Cluster Complex with a Side-On-Coordinated Carbene Ligand with Sulfur Compounds Resulting in the Formation of a Thioketone Complex (pages 993–995)

      Dr. Jochem U. Köhler, Prof. the Lord Jack Lewis and Dr. Paul R. Raithby

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609931

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      The thiol complex 2 is formed when the side-on-coordinated carbene ligand of cluster complex 1 reacts with H2S/DBU. Abstraction of a hydride from complex 2 yields the thioketone complex 3 in a reversible reaction. A mechanism is proposed in which the hydride abstraction with [Ph3C][BF4] proceeds by transfer of a proton from the thiol group to the cyclohexadienyl ring bearing an anionic charge. The hydrogen is finally removed as a hydride. DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene.

    9. Metalated Tetra- and Penta(cyclopentadienyl)-cyclopentadienyl Compounds: Syntheses by Multiple Pd-Catalyzed Cyclopentadienylations (pages 995–998)

      Prof. Dr. Roland Boese, Dr. Gabriele Bräunlich, Dr. Jean-Pierre Gotteland, Dr. Jenn-Tsang Hwang, Dr. Carsten Troll and Prof. Dr. K. Peter C. Vollhardt

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609951

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      A one-step synthesis of the penta(cyclopentadienyl)cyclopentadienyl complex 1 can be achieved from [Mn(η5-C5I5)(CO)3] and CpSnMe3. Complex 1 can be converted to the corresponding novel pentaanion by reaction with BuLi. Because of their topography these compounds are interesting with regard to the construction of metalated semibuck-minsterfullerenes and metallobuckminsterfullerenes.

    10. A Novel Heterobimetallic Layered Compound Showing Ferrimagnetism (pages 998–1000)

      Prof. Dr. Jinkwon Kim, Jin Mook Lim, Prof. Dr. Yong-Kook Choi and Prof. Dr. Youngkyu Do

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199609981

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      Tethering manganese(II) and copper(II) ions with the dianion of (bis(methylthio)methylidene)malonic acid gives a two-dimensional ferrimagnetic layer compound. The layers are stacked with sulfur-sulfur interactions between the methylthio side arms; a section from the crystal structure is shown on the right.

    11. The First Carborane with a Distorted Cuboctahedral Structure (pages 1000–1002)

      Prof. Dr. Narayan S. Hosmane, Dr. Hongming Zhang, Prof. Dr. John A. Maguire, Dr. Ying Wang, Dr. Colacot J. Thomas and Thomas G. Gray

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199610001

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      As intermediates in the rearrangement of icosahedral 1,2-carboranes to give the corresponding 1,7-carboranes, carboranes with cuboctahedral structure were postulated by Lipscomb in the 1960s. The first example of this type of carborane, (CSiMe3)4B8H8, has now been prepared and characterized (X-ray crystal structure on the right). The stability of this compound and the minor deviation of the C4B8 frame from cuboctahedral geometry can be explained by the steric demand of the silyl substituents.

    12. The Dianion of Tetraphenylgermole is Aromatic (pages 1002–1004)

      Prof. Robert West, Honglae Sohn, Dr. Douglas R. Powell, Dr. Thomas Müller and Prof. Yitzhak Apeloig

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199610021

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      Not one, but two structurally distinct forms are obtained depending upon the crystallization temperature when Li2([PhC]4Ge) crystallizes from dioxane. In one form (left) the two lithium iòns are located on opposite sides of the germole rings each η5 coordinated to all of the ring atoms. In the other form (right), one lithium ion is η5 coordinated to the ring atoms and the other is η1 coordinated to the germanium center. The C[BOND]C distances within the ring of the germole dianion are nearly equal, indicating that the bonding is highly delocalized.

    13. A Trinuclear Organoantimony Cation: Structure of [Me2Sb[BOND]Sb(Me2)[BOND]SbMe2][Me2SbBr2] (pages 1005–1006)

      Prof. Dr. Hans Joachim Breunig, Michael Denker and Dr. Enno Lork

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199610051

      Only stable in the crystal, the title compound 1 contains the first example of a polynuclear organoantimony cation. Interionic Sb … Sb and Sb … Br contacts are observed in 1, and reversible dissociation of 1 in solution gives the starting materials Me2SbBr and Me4Sb2. These components exchange Me2Sb groups in the formation of 1.

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    14. Na14K6Tl18M (M = Mg, Zn, Cd, Hg) and Na13.5Sm0.5K6Tl18Na: Novel Octahedral and Centered Icosahedral Cluster Phases Related to the Mg2Zn11-Type Structure (pages 1006–1009)

      Dr. Zhen-Chao Dong and Prof. John D. Corbett

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199610061

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      The cubic Na14K6TI18M Zintl phases (M = Mg, Zn) are not only derivatives of the Na4K6Tl13 structure, but also isopointal with the Mg2Zn11, Mg2Al5Cu6, and Na2In5Au6 intermetallic compounds. The section of the structure shown on the right depicts the two cation types and the isolated Tl octahedra and Tl12M icosahedra. A wide variety of bonding interactions and tuning prospects are evident.

    15. A Double Calix[4]arene in a 1,3-alternate Conformation (pages 1009–1011)

      José-Antonio Pérez-Adelmar, Dr. Hervé Abraham, Dr. Concha Sánchez, Prof. Dr. Kari Rissanen, Prof. Dr. Pilar Prados and Prof. Dr. Javier de Mendoza

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199610091

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      Tightly packed infinite zeolite-like tubes with an inner diameter of 4.1 – 4.5 Å are formed by the novel double calixarene in the solid state (see schematic representation of the crystal structure on the right). In solution, the calixarene binds Ag1 cations, both at the ends and inside the cylindrical cavity.

    16. A Stable Tetraazafulvalene (pages 1011–1013)

      T. Andrew Taton and Prof. Dr. Peter Chen

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199610111

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      A genuine double bond joins the two imidazol-2-ylidene halves in compound 1, which was characterized by both X-ray crystallography and NMR spectroscopy. The dissociation of 1 to 1′ was not observed, even though the strength of the C[DOUBLE BOND]C bond is estimated to be only a few kcalmol−1. This is in accordance with theoretical predictions based on the very large singlet–triplet energy difference for the imidazol-2-ylidenes. Dissociation of the unbridged, singly bridged, or larger ring doubly bridged tetraazafulvalenes is therefore an entropy-driven process.

    17. Synthesis and Characterization of Bis(chlorin)s from the McMurry Reaction of Formylchlorins (pages 1013–1016)

      Dr. Laurent Jaquinod, Daniel J. Nurco, Dr. Craig J. Medforth, Dr. Ravindra K. Pandey, Timothy P. Forsyth, Dr. Marilyn M. Olmstead and Prof. Dr. Kevin M. Smith

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199610131

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      The first ethylene-bridged bis(chlorins) (for example 1) were obtained by coupling reactions of formylchlorins, either as the nickel(II) or zinc(II) complexes, with lowvalent titanium. They can be partially oxidized at reflux in toluene/acetic acid to afford trans-chlorin/porphyrin compounds, or fully oxidized with isomerization to the cis-configured bis(porphyrin)s.

    18. Oxindigo: Color Deepening, Strong Fluorescence, and Large Stokes Shift by Donor-Substitution (pages 1016–1019)

      Prof. Dr. Heniz Langhals and Dr. Barbara Wagner

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199610161

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      Donor groups in positions 6 and 6′ transform trans-oxindigo into bathochromically absorbing fluorescent dyes, such as 1a, with a large Stokes shift. The cis isomer 1b exhibits an even larger bathochromic shift and an intense solid-state fluorescence that extends far into the NIR region.

    19. Synthesis of Novel Difluoroprostacyclin Derivatives: Unprecedented Stabilizing Effect of Fluorine Substituents (pages 1019–1021)

      Takashi Nakano, Mayumi Makino, Dr. Yoshitomi Morizawa and Yasushi Matsumura

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199610191

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      Markedly more stable than the natural product, di-fluoroprostacyclin 1 inhibits ADP-induced human platelet aggregation better than any other known prostacyclin derivative. Key steps in the synthesis of 1 are fluorination of the Corey lactone with (Ph-SO2)2NF in the presence of MgBr2 and subsequent Wittig reaction to attach the α side chain.

    20. Charge Transfer Interactions in Dyed Crystals of Aromatic Carboxylic Acids and Their Relevance to MALDI Mass Spectrometry (pages 1021–1023)

      Christine A. Mitchell, Scott Lovell, Keith Thomas, Dr. Phil Savickas and Dr. Bart Kahr

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.199610211

      A new facet of an old theme! Dyed crystals of aromatic carboxylic acids, a common topic in the scientific literature 100 years ago, are rarely discussed today. These mixed crystals are now reintroduced as superior model systems for studying the host–guest interactions that are so important in MALDI mass spectrometry. Orientations for included dyes are determined through polarization spectroscopy. The role of charge transfer is indicated by the X-ray structure of Malachite Green · hydrogen phthalate.

  4. Book Reviews

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