Angewandte Chemie International Edition in English

Cover image for Vol. 20 Issue 6‐7

June/July 1981

Volume 20, Issue 6-7

Pages 487–616

Currently known as: Angewandte Chemie International Edition

  1. Reviews

    1. Top of page
    2. Reviews
    3. Communications
    4. Book Reviews
    1. The Kinetics of Intramolecular Reactions from Relaxation Time Measurements (pages 487–500)

      Prof. Joseph B. Lambert, Dr. Ronald J. Nienhuis and Joe W. Keepers

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198104873

      An insight into very rapid intramolecular processes, e.g. the rotation of methyl groups, is possible by measurement of dipole-dipole and quadrupole relaxation times. Spin-lattice relaxation provides an alternative to the standard line-shape analyses. Furthermore it expands the NMR range at both the high and the low energy barrier limits.

    2. Molecular Self-Organization and the Origin of Life (pages 500–520)

      Prof. Dr. Hans Kuhn and Prof. Dr. Jürg Waser

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105001

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      A model for the existence of life starts from the principle of a sequence of many small physically and chemically plausible steps which lead to the self-organization of matter. The motivating force is considered to be, inter alia, the periodic change of temperature on a prebiotic planet.—The specific model described leads to assertions about the prerequisites, logical framework, and organizational structure of evolutionary processes.

    3. N-Methyl Inversion Barriers in Six-membered Rings (pages 521–529)

      Prof. Dr. Alan R. Katritzky, Dr. Ranjan C. Patel and Dr. Frank G. Riddell

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105211

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      In conformational studies on N-methylated oligoazacyclohexanes it is purposeful to regard the energy barrier for N-methyl inversion as two “half-barriers” for the steps equatorial form [e.g. (1e)][RIGHTWARDS ARROW]transition state and axial form [e.g. (1a)][RIGHTWARDS ARROW]transition state, since the one or the other half-barrier is involved, depending on the method of measurement. Such an approach is of particular interest in the case of compounds containing several methylated nitrogen atoms in the six-membered ring.

    4. Benzvalene—Properties and Synthetic Potential (pages 529–546)

      Prof. Dr. Manfred Christl

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105291

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      Benzvalene (1), the best investigated valence isomer of benzene, was first prepared in 1967 via the route outlined below. Interactions with the σ-system bestow extraordinary reactivity on the double bond of the highly strained hydrocarbon (1).—Benzvalene secondary products are described systematically.

    5. Intermolecular Forces—An Example of Fruitful Cooperation of Theory and Experiment (pages 546–568)

      Prof. Dr. Peter Schuster

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105461

      Detailed information about aggregates of atoms, small ions and/or small molecules in the vapor phase, which are held together by intermolecular forces, has been obtained by new experimental techniques and extended ab initio calculations. Theory and experiment are often complementary regarding reliable predictions.

  2. Communications

    1. Top of page
    2. Reviews
    3. Communications
    4. Book Reviews
    1. Michael Addition of Lithium Acetylides to Propenyl Trityl Ketone (pages 569–570)

      Dipl.-Chem. Rita Locher and Prof. Dr. Dieter Seebach

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105691

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      The direct 1,4-addition of lithium acetylides is achieved by use of propenyl trityl ketone Ph3C[BOND]CO[BOND]C[DOUBLE BOND]CH[BOND]CH3 as Michael acceptor. The 4-alkynones (1) (R = e.g. n-C5H11) that are formed can be reductively cleaved with LiBHEt3 to the alcohols (2), which are very useful synthetic building blocks.

    2. Cyclopentadienethione (pages 570–571)

      Dipl.-Chem. Reinhard Schulz and Prof. Dr. Armin Schweig

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105701

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      A novel cyclic thioketone, the title compound (2), was obtained by gas-phase pyrolysis from the educts (1) or (3), and identified PE spectroscopically. (2), a yellow oil, forms crystals on standing.

    3. 4,13-Diaza[24](1,2,4,5)cyclophane and 4,16-Diaza[24](1,2,4,5)-cyclophane (pages 571–572)

      Hee Chol Kang and Prof. Dr. Virgil Boekelheide

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105711

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      A cyclophane analogue of pyrazine, the 4, 16-diaza[24](1,2,4,5)cyclophane (1) is of special interest as a complex ligand. It was synthesized, like its 4, 13-diaza-isomer (2), by gas-phase pyrolysis.

    4. Non-planar Double Bonds and Increased Reactivity in Olefins with Low Strain (pages 572–573)

      Dr. Ulrich Burkert

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105721

      Norbornene and norbornadiene contain non-planar double bonds; these findings from ab initio calculations have now been confirmed by force field calculations (molecular mechanics). If the non-planarity of the double bonds in the two compounds mentioned is explained in terms of torsional strain, then the same effect can be predicted for other cyclic olefins, inter alia, for cyclopentene.

    5. Alkylation of Donor-Acceptor Substituted Cyclopropanes: A Flexible Route to 4-Oxocarboxylic Acid Esters (page 574)

      Ingrid Böhm, Elisabeth Hirsch and Dr. Hans-Ulrich Reissig

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105741

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      Siloxy-substituted cyclopropanecarboxylates (1) have been deprotonated for the first time and alkylated to (2); the highly substituted cyclopropanes (2) can then be cleaved in very good yields by fluoride ions to give 4-oxocarboxylates (3), which are valuable synthetic building blocks for natural products.

    6. A Novel Route to 2-Ethoxybutadienes; Diels-Alder Reaction of 1,2-λ5-Oxaphosphorines (pages 575–576)

      Prof. Dr. Hans-Jürgen Bestmann and Dipl.-Chem. Kurt Roth

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105751

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      2-Ethoxybutadienes—enol ethers of α,β-unsaturated carbonyl compounds universally applicable as synthons can be prepared from primary alkyl halides, carboxylic acid derivatives and aldehydes as alkyl- and aryl-substituted derivatives (1) as well as acyl derivatives (2). Intermediary acylphosphoranes cyclize in part to 1,2-λ5-oxaphosphorines, which function as dienes in Diels-Alder reactions.

    7. Synthesis of (±)-13-Deoxo-11-deoxydaunorubicinone (pages 576–577)

      Prof. Dr. Karsten Krohn

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105761

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      The naturally occurring title compound (2), an interesting antibiotic, has been synthesized for the first time. The key step was cyclization of the 2,3-dialkylated anthraquinone (1), which proceeded in 70 % yield.

    8. Bis(2,2,2-trichloro-1,1-dimethylethyl) Monochlorophosphate, a Selective Reagent for the Phosphorylation and Protection of the 5′-OH Group of Nucleoside Derivatives (pages 577–578)

      Dr. Herbert A. Kellner, Dipl.-Chem. Ruth G. K. Schneiderwind, Dr. Heiner Eckert and Prof. Dr. Ivar K. Ugi

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105771

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      The selective protection of the 5′-position of thymidine (2) can be accomplished with the reagent (1), R = Cl3C[BOND]C(CH3)2. The protecting group survives all reactions necessary for oligonucleotide syntheses. The 5′-phosphate (3) can then be obtained by reductive cleavage of residue R—without intermediary regeneration of a free 5′-OH group.

    9. Redox Reltionship between Carbeneiron and σ-Alkyliron Porphyrins (pages 578–579)

      Dr. Doris Lexa, Prof. Jean-Michel Savéant, Dr. Jean-Paul Battioni, Dr. Marc Lange and Dr. Daniel Mansuy

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105781

      σ-Alkyliron porphyrins, both with FeII as well as with FeIII can be generated from carbeneiron (II) porphyrins by cyclovoltammetric reduction. (TPP) Fe(HC[DOUBLE BOND]CPh2)—a σ-vinyl-FeII complex–was also independently synthesized from (TPP)Fe(ClO4) and BrMg[BOND]CH[DOUBLE BOND]CPh2; its properties resemble those of the product of the (2e + H)-reduction of (TPP) Fe(:C[DOUBLE BOND]CPh2).

    10. Triepoxides of Bicyclo[4.2.0]octa-2,4,7-triene (pages 580–581)

      Prof. Dr. Waldemar Adam, Dr. Omar Cueto, Dr. Ottorino De Lucchi, 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.198105801

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      Three of the six isomeric triepoxides of the bicyclotriene (1) could be synthesized via the endoperoxide (2). X-ray structure analyses have been carried out on (3a)–(3c).

    11. Facile Nucleophilic Silylation Reactions at Carbonyl Functionalities Using Trimethylsilylaluminum Compounds (pages 581–582)

      Priv.-Doz. Dr. Lutz Rösch, Dr. Gerald Altnau and Dr. Wolfgang Helmut Otto

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105811

      In order to check whether organic compounds can be nucleophilically silylated with Me3Si[BOND]Al compounds such as (1) and (2), the latter were allowed to react with an aldehyde, a ketone, and an acid. Complexing agents like diethyl ether and AlCl3 have considerable influence on the reactions. Summary: Reagents (1) and (2) can be used for the directed nucleophilic silylation of carbonyl compounds; α-hydroxytrimethylsilyl derivatives are formed. An advantage is the absence of undesirable by-products.

      • equation image
    12. Trimethylsilylaluminium Compounds as Catalyst Components in the Polymerization of Ethene (pages 582–583)

      Priv.-Doz. Dr. Lutz Rösch and Dr. Gerald Altnau

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105821

      Can the alkylaluminum compound in Ziegler-Natta catalysts be replaced by asi lylaluminum compound? TiCl4/Al(SiMe3)3·Et2O (5:2), for example, has proven to be a suitable catalyst for the polymerization of ethylene. This is the first catalyst in which no transition metal-carbon but a transition metal-silicon bond might be present, at least in the first polymerization step.

    13. Novel Molecules of the Phane-type with p-Benzoquinone and Oxahomobenzene Moieties (pages 583–585)

      Dr. Ihsan Erden, Dr. Peter Gölitz, Dr. Reinhard Näder and Prof. Dr. Armin de Meijere

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105831

      Thumbnail image of graphical abstract

      The functionalization of paracyclophanedione has proven a convenient route compounds of type (1) and (2); usually the functional groups are introduced at a precursor stage. Such compounds are suitable as models for the study of intramolecular interactions.

    14. A Novel Method of CC-Bond Formation: Thermolytic Elimination of Sulfur and Hydrogen Halides from α-Halosulfides (pages 585–586)

      Dr. Jean-Claude Pommelet, Dipl.-Chem. Claire Nyns, Francis Lahousse, Dipl.-Ing. Robert Merényi and Prof. Dr. Heinz G. Viehe

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105851

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      A three-step synthesis of the acrylic acid or acrylonitrile derivatives (2) uses thiols and α-halocarboxylic acids or -nitrites as starting materials. The central intermediates are the α-halosulfides (1), which give (2) on gas-phase pyrolysis: the mechanism of this rearrangement resembles that of the Ramberg-Bäcklund reaction.

    15. A Novel Ylidic Organophosphorus Ligand (pages 586–588)

      Prof. Dr. Hubert Schmidbaur, Dipl.-Chem. Ulrich Deschler and Dipl.-Chem. Beatrix Milewski-Mahrla

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105861

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      A particularly effective combination of the donor properties of phosphanes and phosphorus ylides has been achieved in the chelate system characterized by the resonance structures (A) and (B). Reaction with [(CH3)3P]2NiCl2 leads via alkali metal intermediates to the lemon-yellow, air- and moisture-sensitive complex (1).

    16. A Simple Pyrrole Synthesis via an Unusually Facile 1,3 Shift in N-Benzyl-N-(2-benzylaminocyclopropyl)-N-benzylideneammonium Ions (pages 588–589)

      Prof. Dr. Helmut Quast, Dipl.-Chem. Wolfgang von der Saal and Dr. Josef Stawitz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105881

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      The key step of a new, simple synthesis of pyrrole from (substituted) 1,2-bis(benzylamino)cyclopropanes and aromatic aldehydes is the ring expansion (1)[RIGHTWARDS ARROW](2). In the last step benzylammonium ions are cleaved off.

    17. An Unsual Double Intramolecular Cyclization—Structural Analysis of 2,6-Dibromo-4,8-dimethyltetracyclo[3.3.0.02,8.0 4,6]octane-3,7-dione (pages 589–591)

      Dr. Krystina Kratzat, Priv.-Doz. Dr. Franz W. Nader and Thea Schwarz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105891

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      Not the expected bisallenedicarboxylate, but the cage dione (2) is formed on reaction of the bicyclopropyldicarboxylate (1) with tBuLi. X-ray structure analysis of (2) confirms the spectroscopically established assignments.

    18. A Diorganotin Oxide with a Planar Tin-Chalcogen Six-Membered Ring (page 591)

      Prof. Dr. Heinrich Puff, Willi Schuh, Dr. Rolf Sievers and Dr. René Zimmer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105911

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      The first compound containing a planar (SnO)3-ring is a form of (1) readily soluble in organic solvents, even in the cold; (1) was obtained on reaction of tBu2SnCl2 with NaOH in boiling toluene. So far only sparingly soluble (1)–probably polymeric in the solid state–was known.

    19. Coordination of Dimethyl(thionitroso)amine to Pentacarbonylchromium via the Sulfur Atom (pages 591–592)

      Prof. Dr. Herbert W. Roesky, Ralf Emmert, Dr. William Clegg, Dipl.-Chem. Wilhelm Isenberg and Prof. Dr. George M. Sheldrick

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105912

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      Unstable (1), coordinated to the metal via sulfur and not via nitrogen is the first acyclic sulfur-nitrogen ligand. The 1:1 complex (2) forms stable ruby-red crystals at room temperature.

    20. l,5-Bis(dimethylamino)tetrasulfur Tetranitride–A Cage Molecule with a Non-Symmetric Nitrogen Bridge (pages 592–593)

      Prof. Dr. Herbert W. Roesky, Dr. M. N. S. Rao, Dipl.-Chem. Cornelia Graf, Dr. habil. Alfred Gieren and Dr. Erich Hädicke

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105921

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      S4N4 with two differently oriented dimethylamino ligands is formed on reaction of S4N4Cl2 with Me3SiNMe2. The product (1) is the first S4N4 derivative containing amino groups. One of the dimethylamino ligands forms a non-symmetrical bridge between the positions 1 and 5.

    21. Mononuclear Transition Metal Complexes with CS2-Analogous Coordination of a Thioketene (pages 593–594)

      Prof. Dr. Helmut Werner, Dipl.-Chem. Oswald Kolb, Dipl.-Chem. Dr. Ulrich Schubert and Dipl.-Chem. Klaus Ackermann

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105931

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      Model substances for the complex chemical fixation of CO2 include, as most interesting, CS2 and analogous ligands such as 1,1,3,3-tetramethyl-2-thiocarbonylcyclohexane (1). This ligand is distinguished by the formation of mononuclear Co- und Rh-complexes.

    22. Bis(tetraphenylphosphonium) Hexadecaphosphide, a Salt Containing the Novel Polycyclic Anion Pmath image[1] (pages 594–595)

      Prof. Dr. Hans Georg von Schnering, Dipl.-Chem. Victor Manriquez and Dr. Wolfgang Hönle

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105941

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      The novel hexadecaphosphorus dianion Pmath image, formed on suspension of Na3P7 in THF, could be trapped with Ph4PCl. Aside from the red crystals of the title compound, yellow amorphous “higher phosphanes” are formed.

    23. Stereoselective Cyclopropane Syntheses by “Oxy-Homodienyl Hydrogen Shifts” (pages 595–596)

      Prof. Dr. Frank-Gerrit Klärner, Dipl.-Chem. Wolfgang Rüngeler and Werner Maifeld

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105951

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      The stereoselective rearrangement of hexadienols (1) into cyclopropylacetaldehydes (2), R4 = H, or cyclopropylmethyl methyl ketones (2), R4 = CH3, takes place by “oxy-homodienyl hydrogen shift”. In the case of the corresponding hydrocarbons the equilibrium is on the side of the acyclic diene.

    24. Silaethene (pages 597–598)

      Prof. Dr. Günther Maier, Dipl.-Chem. Gerhard Mihm and Dr. Hans Peter Reisenauer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105971

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      H2Si[DOUBLE BOND]CH2, the simplest compound with Si[DOUBLE BOND]C double bonding was generated by retrodiene cleavage from the bicycle (1), X = H, isolated in an argon matrix at 10 K, and identified by IR and UV spectra. On warming, (2) (X = H) is formed. Derivatives with X = D and X = Cl behave analogously.

    25. Silaethene: Highly Correlated Wave Functions and Photoelectron Spectroscopic Evidence (pages 598–599)

      Dr. Pavel Rosmus, Prof. Dr. Hans Bock, Dr. Bahman Solouki, Prof. Dr. Günther Maier and Dipl.-Chem. Gerhard Mihm

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105981

      For the PE-spcctroscopic search for H2Si[DOUBLE BOND]CH2-generating reactions its first ionization energy was initially estimated by quantum chemical ab initio methods. In a wide range of pyrolysis experiments no reproducible bands could be observed in the expected region. A new band with vibrational fine structure, however, occurred on thermal retrodiene cleavage of the silabicycle (1), X = H (see previous communication). The assignment is supported by further arguments.

    26. The “Antiaromaticity” of l,4-Dihydropyrazines (pages 599–600)

      Dr. Wolfgang Kaim

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198105991

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      The influence of the 8π-electron structure on the proton resonance has been studied in the case of compounds (1)(6). If the paramagnetic ring current is considered as criterion, only (1) and (2) are antiaromatic (R = CH3).

    27. Organometal-Stabilized 1,4-Dihydropyrazines: Extremely Electron-Rich Heterocycles (pages 600–601)

      Dr. Wolfgang Kaim

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198106001

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      The long predicted electronic structure of the 1,4-dihydropyrazines has been confirmed PE-spectroscopically, inter alia, on the model compounds (1) and (2), R = CH3. These measurements gave extremely low ionization potentials for the heterocycles; (2) holds the record, with IEmath image = 5.87 eV (for comparison: Na = 5.1 eV).

    28. Model Reactions for the Stereo-Controlled Synthesis of Aminopolyols; Reduction of Isoxazolines with Free or Protected Hydroxy Groups in Position 4 or in Side Chains (pages 601–603)

      Prof. Dr. Volker Jäger, Dr. Wilfried Schwab and Volker Buss

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198106011

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      The effects of substituents on asymmetric induction in hydride additions have been investigated on isoxazoline derivatives; the results, which are of importance for the synthesis of hydroxylated amino acids, sphingolipid bases or amino sugars, can be rationalized with the models (1) and (2).

    29. 4-Hydroxylation of Isoxazolines; Synthesis of rac-Phytosphingosine (ribo-2-Amino-1,3,4-octadecanetriol) (pages 603–605)

      Dr. Wilfried Schwab and Prof. Dr. Volker Jäger

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198106031

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      The shortest and most effective phytosphingosine synthesis so far was achieved after a concept, according to which various amine sugars can be easily “assembled”. The two decisive steps in the preparation of the title compound (3), which proceed highly stereoselectively, are the hydroxylation of the isoxazoline (1) and the LiAlH4-reduction of (2).

    30. Allosteric Effects: Binding Cooperativity in a Subunit Model (pages 605–606)

      Prof. Dr. J. Rebek, R. V. Wattley Jr., T. Costello, R. Gadwood and L. Marshall

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198106051

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      The macrobicyclic polyether (1) is the first “small” model system which exhibits a binding cooperativity. It could be shown by 600-MHz 1H-NMR studies that binding of one Hg(CN)2 to (1) increases its binding ability for a second Hg(CN)2 by a factor of ten.

    31. Contrasting Behavior in the Substitution Reactions of 9-(2-Bromomethyl-6-methylphenyl)fluorene Rotamers (pages 606–607)

      Shigeru Murata, Seiichiro Kanno, Yo Tanabe, Dr. Mikio Nakamura and Prof. Dr. Michinori Ōki

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198106061

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      The rotameric fluorene derivatives sp-(1) and ap-(1) exhibit different behavior: in SN2 reactions the sp-form reacts more rapidly than the ap-form; on the other hand, in SN1 reactions—e.g. heating in CF3CO2H/CHCl3, only the sp-rotamer participates.

    32. peri-Substituent Effects on the Rotational Barrier of 9-(1,1-Dimethyl-2-phenylethyl)triptycene (pages 607–608)

      Dr. Gaku Yamamoto, Masahiko Suzuki and Prof. Dr. Michinori Ōki

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198106071

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      The rotation barrier in compounds of type (1), whose stable rotamer is the ap-form, depends very strongly on the size of the peri-substituents. In derivatives with X = F and OCH3 the barrier is smaller, in those with X = CH3 and Cl, greater than in the parent compound with X = H.

    33. P-Functionalized Diferriophosphonium Salts and Complex-Stabilized Derivatives of Phosphinic Acid (pages 608–610)

      Priv.-Doz. Dr. Hans Schäfer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198106081

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      Crystalline, air-stable, PH2-bridged iron complexes (1), X = Cl, Br or BPh4, have been prepared for the first time. The activated P[BOND]H bonds enable the synthesis of derivatives, e.g. of the diferriophosphinic acid derivative (2), a neutral dimeric compound in the crystalline state.

    34. Regio- and Stereoselective “Long-Range” Hydroxylation of Cholestanes–A Novel Route to 5α-Steroids with cis-Coupled A, B-Rings (pages 610–611)

      Dr. Jean-Pierre Bégué

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198106101

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      Regio- and stereoselective synthesis via carbenium ions seldom succeed so well as the γ-hydroxylation of cyclohexane derivatives via α-acylcarbenium ions. This method can also be applied to cholestanes: the bromide (1), affords the hydroxyketone (2) in 45% yield.

    35. Synthesis of a Novel Biscarbene Type of Complex[1] (pages 611–612)

      Prof. Dr. Ernst Otto Fischer, Dipl.-Chem. Werner Röll, Priv.-Doz. Dr. Ulrich Schubert and Dipl.-Chem. Klaus Ackermann

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198106111

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      o-Dilithiobenzene adds hexacarbonylchromium, -molybdenum or tungsten; alkylation of the intermediates leads to the 1,4-chelated biscarbene complexes (1)(3), which are stable as permanganate-colored to black leaflets at room temperature. Spectroscopic studies show that these compounds have a distorted octahedral structure.

    36. Simple Synthesis of l,3-Dialkyl-4,5-dihalo-2(3H)-imidazolones (pages 612–613)

      Prof. Dr. Heinrich Wamhoff, Dipl.-Chem. Wolfgang Kleimann, Dipl.-Chem. Gerhard Kunz and Dr. Christoph H. Theis

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198106121

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      Dialkylparabamic acids (3) and other products can be obtained from the 2(3 H)-imidazolone derivatives (2). A facile entry to the heterocycles (2) is the double alkylation of substituted imidazoles (1); the imidazolium salts formed are converted with NaOH into (2).

    37. The Unusual Stereochemistry of the Cycloaddition of Vinyl Ethers with Sulfonyl Isothiocyanates (pages 613–615)

      Prof. Dr. Ernst Schaumann, Dr. Hans-Günther Bäuch and Dr. Gunadi Adiwidjaja

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198106131

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      Interesting consequences of heteroallene cycloadditions are observed in the title reaction: the cis-vinyl ether (1), R1 = R3 = H, R2 = Me, R4 = Et, reacts with (2), R = Me, to give 98 ± 2% cis-(3), which partially isomerizes to the trans product; on the other hand, on starting with trans-(1), 33–42% cis-(3) is obtained. These findings are explained in terms of the formation of a zwitterionic intermediate in which direct ring closure and rotation about the original π-bond in (1) compete.

  3. Book Reviews

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    2. Reviews
    3. Communications
    4. Book Reviews

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