Angewandte Chemie International Edition in English

Cover image for Vol. 26 Issue 12

December 1987

Volume 26, Issue 12

Pages 1201–1324

Currently known as: Angewandte Chemie International Edition

    1. Cover Picture (Angew. Chem. Int. Ed. Engl. 12/1987)

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712011

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      The cover shows the coat of arms of the city of Mainz and two ends of the formula of a new “trimesogen.” Heraldry as source of chemical inspiration? The “Wheel of Mainz” as liquid crystal? A ludicrous, by no means scientific question? Certainly not! The study of the structure-property relationships of new compounds and their directed synthesis (molecular engineering, molecular design) is one of the fascinating problems of modern organic chemistry. The wheel of Mainz has, at first glance, nothing to do with liquid crystal research. However, if one is concerned with the molecular combination of disk- and rod-shaped mesogens one cannot avoid this historical geometry. The translation of the structure of the “Wheel of Mainz” into a molecular structure is reported on by H. Ringsdorf et al. on page 1249.

      The cover illustration prompts the editor to take this opportunity of inviting readers and authors to the forthcoming University Lecturers' Conference (March 13–16, 1988) in Mainz, when Angewandte Chemie will celebrate its centenary.

  1. Reviews

    1. Top of page
    2. Reviews
    3. Communications
    4. Correspondences
    5. Corrigenda
    6. Book Reviews
    7. Author Index
    8. Subject Index
    1. Chemistry of the Silicon-Silicon Double Bond (pages 1201–1211)

      Prof. Robert West

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712013

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      The concept of “embedding” reactive double bonds by bulky substituents has made it possible to isolate disilenes such as 1 as thermally stable, yellow or orange colored crystalline compounds. Structural and spectroscopic studies indicate many similarities between the (3p–3p)π bonding in disilenes and the (2p-2p)π bonding in olefins.

    2. Modern NMR Spectroscopy of Organolithium Compounds (pages 1212–1220)

      Prof. Dr. Harald Günther, Dr. Detlef Moskau, Dipl.-Biol. Peter Bast and Dipl.-Chem. Dietmar Schmalz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712121

      Detailed information on the structure and modes of reaction of the title compounds, which are of importance in organic synthesis, can be obtained with modern techniques of NMR spectroscopy. In particular two-dimensional methods open up new possibilities in the field of organolithium compounds, where the combination of 1H-, 13C-, and 6(7)Li-NMR spectroscopy is especially useful. Thus, homo- and heteronuclear shift correlations enable the complete assignment of 1H-, 13C-, and 6(7)Li-NMR spectra and hence yield important information about the aggregates and complexes present in solution. Further information is provided by nuclear Overhauser experiments and exchange spectroscopy.

    3. Molecular Dynamics of Elementary Chemical Reactions (Nobel Lecture) (pages 1221–1243)

      Prof. Dudley R. Herschbach

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712211

      That his Nobel lecture might be regarded as a tour through a family album is the view expressed by D. R. Herschbach in a note of thanks to his co-workers. The following citation might serve as a stimulus for reading this lecture: “As urged by my students, on this occasion I want both to view our still youthful field of research from a wider perspective and to recount some favorite instructive episodes from its infancy. I will also briefly discuss several prototype reactions which have served to develop heuristic models and to reveal how electronic structure governs the reaction dynamics.”–Note: The Nobel lectures of Y.-T. Lee and J. C. Polanyi who were awarded the Nobel prize together with D. R. Herschbach, have already appeared in the October issue of the journal.

  2. Communications

    1. Top of page
    2. Reviews
    3. Communications
    4. Correspondences
    5. Corrigenda
    6. Book Reviews
    7. Author Index
    8. Subject Index
    1. Molecular Recognition: Stacking Interactions Influence Watson-Crick vs. Hoogsteen Base-Pairing in a Model for Adenine Receptors (pages 1244–1245)

      Prof. Julius Rebek Jr., Kevin Williams, Dr. Kevin Parris, Dr. Pablo Ballester and Dr. Kyu-Sung Jeong

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712441

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      Despite ideal conformation of the two naphthyl esters 1a, b in the solid state, they do not form any edge-to-face associates with 9-ethyladenine in solution. Rather, as detailed NOE and 2D-NOESY NMR measurements have shown, face-to-face associates such as 2 are preferentially formed by stacking interactions, whereby the nature of the base pairing and the bond strengths can be engineered as desired by variation of the substituents.

    2. 2,3,9,10-Tetrakis(trimethylsilyl)[5]phenylene. Synthesis via Regiospecific Cobalt-Catalyzed Cocyclization of 1,6-Bis(triisopropylsilyl)-l,3,5-hexatriyne (pages 1246–1247)

      Dr. Luis Blanco, Harold E. Helson, Dr. Michael Hirthammer, Dr. Helene Mestdagh, Dr. Spyros Spyroudis and Prof. Dr. K. Peter C. Vollhardt

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712461

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      The highest homologue of the [n]phenylenes thus far isolated, the title compound 1, is a deep-red, extremely air-sensitive crystalline compound. A newly developed strategy for the synthesis of such hydrocarbons has proven to be extremely efficient: cocyclization of tetraethynylbenzene with the hexa-triyne iPr3Si[BOND]C[TRIPLE BOND]C[BOND]C[TRIPLE BOND]C[BOND]C[TRIPLE BOND]C[BOND]SiiPr3 leads to a [3]phenylene, which, in turn, is likewise a tetraethynyl compound and can thus be employed in renewed cocyclizations.

    3. Cyclohepta[a]phenalene: A Highly Electron-Donating Nonalternant Hydrocarbon (pages 1247–1249)

      Dr. Yoshikazu Sugihara, Hiromasa Yamamoto, Kenji Mizoue and Prof. Dr. Ichiro Murata

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712471

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      The title compound 1, which forms green needles and can be stored under N2 at 0°C, is just as easy to oxidize as tetrathiafulvalene. The key step of the synthesis of this first un-substituted Reid-hydrocarbon, starting from readily available 1,8-diiodonaphthalene, is a benzene ring expansion by intramolecular ketocarbene addition. According to the NMR data, compound 1 is best described as a double vinylogous phenylheptafulvalene.

    4. The “Wheel of Mainz” as a Liquid Crystal?—Structural Variation and Mesophade Properties of Trimeric Descotic Compounds (pages 1249–1252)

      Dr. Willi Kreuder, Prof. Dr. Helmut Ringsdorf, Dipl.-Phys. Otto Herrmann-Schönherr and Prof. Dr. Joachim H. Wendorff

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712491

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      Three molecular combinations, each consisting of two disk-shaped (tripheny-lene units) and one rod-shaped mesogen (azobenzene- and azobophenyl-units) were synthesized with the aim of generating new liquid crystal phases. Two molecular geometries were realized thereby. The trimesogen 1 with laterally fixed rod-like mesogen (“Wheel of Mainz”) crystallizes unexpectedly well, while another trimesogen with terminally fixed rod-like mesogen leads to a novel liquid-crystal phase.

    5. Relay Conjugation via Twisted Six- and Seven-Membered Rings (pages 1252–1253)

      Prof. Dr. Rolf Gleiter, Dr. Bernd Kissler and Prof. Dr. Camille Ganter

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712521

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      The energies of the formally degenerate π orbitals of 1–3 differ by 0.7 to 1.3 eV. The PE spectroscopically determined splitting is due to the interaction between the symmetry-adapted n orbitals and certain a orbitals of the twisted central ring. This has been verified by quantum chemical calculations.

    6. Low-Temperature Photolysis of Peracetylated Dodecanoyl Peroxides of Tartaric Acid and D-Gluconic Acid in the Solid State—A Diastereoselective Radical Coupling (pages 1253–1254)

      Dipl.-Chem. Rainer Lomölder and Prof. Dr. Hans J. Schäfer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712531

      The title reaction permits carboxylic acids of the chiral pool to be modified at the asymmetric center with retention of configuration. It is not only preparatively simple but also mechanistically interesting. By steric fixation of radicals in the solid state an otherwise unselective coupling becomes a diastereo-selective one. The chemical yields are 40–60%, the diastereo-selectivities 90–95% de.

      • equation image
    7. Polystannanes Ph3Sn-
      equation image
      SnPh3(n = 1–4): A Route to Molecular Metals? (pages 1255–1256)

      Dr. Stefan Adams and Prof. Dr. Martin Dräger

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712551

      A diminution in the HOMO-LUMO energy difference with increasing chain length in the polystannanes 2 mentioned in the title is indicative of a smooth transition between covalently bound polystannanes and metallic tin and thus affords grounds for answering the question posed in the title in the affirmative. The four polystannanes synthesized according to equation (a) are all-trans-configurated; compound 2, with n[DOUBLE BOND]4, contains the longest Sn[BOND]Sn bond observed so far.

      • equation image
    8. A 3,7-Diaza-l,2,4,5,6,8-hexaphosphatricyclo-[4.2.0.02,5]octane, a [2 + 2] Dimer of a 1,2-Dihydro-l-azatriphosphete containing a Planar P4 Substructure (pages 1256–1257)

      Prof. Dr. Edgar Niecke, Oliver Altmeyer, Martin Nieger and Dr. Fritz Knoll

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712561

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      The yellow crystalline solid 3 is formed upon elimination of Me3SiCl from 1, and a 1-azatriphosphabutadiene and a 1,2-dihydro-l-azatriphosphete are presumably formed as intermediates. According to an X-ray structure'analysis 3 has long P1[BOND]P2 and P5[BOND]P6 bands, thus explaining the relative ease of decomposition into P4 and 2 in solution.

    9. The First 2H-Phosphirene (pages 1257–1259)

      Dipl.-Chem. Oliver Wagner, Prof. Dr. Gerhard Maas and Prof. Dr. Manfred Regitz

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712571

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      In phosphirenes the bonding situation is the opposite of that found in azirines: Whereas the 1Hderivatives are stable in the former, it is the 2Hderivatives which are stable in the latter. The first 2H-phosphirene 3 has sbeen obtained along with 2 by photolysis of the 3H-1,2,4-diazaphospate in pentane at −40°C. An X-ray structure analysis of the “end-on” complex 4 revealed that the P-C bond is remarkably short (1.634(4)%Å).

    10. [{(C5H5)Co}3(C6H5CH[DOUBLE BOND]CHCH3)], an Organometallic Cluster with a Face-Bridging Arene Ligand (pages 1259–1260)

      Dr. Hubert Wadepohl, Klaus Büchner and Dr. Hans Pritzkow

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712591

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      In contrast to the two only known complexes with μ32: η2: η2arene ligands and to benzene on densest packed metal surfaces the title complex 1 exhibits almost complete bond length equalization in the aromatic ring. 1 can be prepared in a one-pot reaction from [CpCo(C2H4)2] and trans-β-methylstyrene or allylbenzene.

    11. Reactions of 2,2,4,4-Tetramethyl-3-methylenecyclobutylidene; Thermal Rearrangements of a 2-Methylenebicyclo[2.1.0]pentane (pages 1260–1262)

      Prof. Dr. Udo H. Brinker and Dipl.-Chem. Wolfgang Erdle

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712601

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      1,3-Insertion in the C[BOND]H bonds of the methyl groups in the carbene 1 leads to formation of the strained 2-methylenebicyclo[2.1.0]pentane 2 as main product. Also formed are 3 and possibly the [l.l.l]propellane4, evidence for which, however, is provided only by the secondary product 5. The thermolysis of 2 affords the first activation parameters for this class of compounds.

    12. Annelated Isoindoles with an 18π-Electron System (pages 1262–1263)

      Prof. Dr. Richard P. Kreher and Dipl.-Chem. Thomas Hildebrand

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712621

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      The isoindoles 1 and 2 can be regarded as radialenes of naphthalene—stabilized by bridging with alkylimino groups. Their differences in structure are manifested in their reactivity: W-methylmaleiimide reacts with a pyrrole ring of 1, but not at all with 2. On the other hand, tetramethyldehydrobenzene reacts with 1 and 2 to give 2:1 cycloadducts (R[DOUBLE BOND]tBu).

    13. Alkyne Complexes of Rhenium in Intermediate Oxidation States; Synthesis and Molecular Structure of a Rhenium(V)-Allenylidene Complex (pages 1263–1265)

      Prof. Dr. Wolfgang A. Herrmann, Roland A. Fischer and Dr. Eberhardf Herdtweck

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712631

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      The ReIV complex 1 undergoes disproportion upon reaction with 2-butyne to give the allylidene-ReV complex 2 and the alkyne-ReIII complex 3. According to an X-ray structure analysis 2 does not have a metallacyclobu-tene structure; rather, the C4 ligand is bound in a carbene/olefin fashion. Reaction of 3 with AgSbF6 in the presence of alkynes leads to bis(π-alkyne) complexes, which are of interest as model compounds for intermediates of oxidative alkyne coupling

      • equation image

      .

    14. Luminescence Probes: The Eu3⊕- and Tb3⊕-Cryptates of Polypyridine Macrobicyclic Ligands (pages 1266–1267)

      Béatrice Alpha, Prof. Dr. Vincenzo Balzani, Prof. Dr. Jean-Marie Lehn, Dr. Siglinda Perathoner and Dr. Nanda Sabbatini

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712661

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      A 104- to 105-times more intense absorption than the corresponding aqua complexes is exhibited by the cryptates 1 and 2; in the latter the ligand absorbs, in the former the metal ion. From the luminescence-lifetimes in H2O and D2O it can be deduced that in Eumath image nine or ten H2O molecules coordinate the Eu3⊕ ion, whereas in 1 only two or three H2O molecules coordinate. Even in 10-5 molar aqueous solutions, 1 and 2 can absorb 1% of the incident UV photons and emit them again as visible light.

    15. Pentasila[1.1.1]propellane. Predictions Concerning Structure, Bonding, and Strain Energy (pages 1267–1268)

      Prof. Dr. Paul von Raguée Schleyer and Prof. Dr. Rudolf Janoschek

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712671

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      A rewarding synthetic target is the title compound 1, only a stretched-bond isomer of which should be stable according to the results of ab initio calculations. The bridgehead Si atoms are 2.73 Å apart, and the bond order between them is only 0.176. This is consistent with the substantial diradical character of the singlet wave function of 1 and with the fact that Si four-membered rings are energetically more favorable than Si three-membered rings.

    16. Electrocyclic Opening of 2,3-Benzo- and 2,3;7,8-Dibenzobicyclo[4.2.0]octa-2,4,7-triene;Benzoannelated Transition States (pages 1268–1270)

      Prof. Dr. Wolfram Grimme, Dr. Johann Lex and Dr. Thomas Schmidt

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712681

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      Benzenoid double bonds readily participate in pericyclic reactions, but this is often masked by a rapid back reaction. It has now been possible to demonstrate this phenomenon in the case of the hydrocarbon 1 deuteriated in position 4; at 100°C, equilibrium is established between 1 and its labeled isomer 1′ via the o-quinoid intermediates 2 and 2′ (K[DOUBLE BOND]1.13, k(100.6°C) = (7.45 ± 0.06)xl0−5s−1).

    17. Synthesis and X-Ray Structure of (2,4,6-Me3C6H2BPC6H11)3: A Boron-Phosphorus Analogue of Borazine (pages 1270–1271)

      H. V. Rasika Dias and Prof. Philip P. Power

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712701

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      A planar B3P3 skeleton with almost equally sized BP bonds characterizes the title compound 1. It can be obtained in 48% yield by reaction of MesBBr3 with C6H11PHLi, and forms pale yellow crystals. Not only planarity and bond-length equivalence but also the BP distance of 1.84 Å suggests an “aromatic” system.

    18. Proof of the (S,S) Configuration of (−)-Bissetone by Synthesis from D-Glucose (pages 1271–1273)

      Dipl.-Ing. Manfred Brehm, Prof. Dr. William G. Dauben, Dr. Peter Kohler and Prof. Dr. Frieder W. Lichtenthaler

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712711

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      (S,S)-Bissetone 1, 2 constituent cf the gorgonian soft coral Briareum polyanthes, can be synthesized in eight steps from D-glucose (overall yield 37%). The central intermediate is the dihydropyranone 2, whose six-step synthesis from D-glucose involving two one-pot reactions has been vastly improved and is now possible on a l00g scale. The conversion of 2 into 1 can be achieved in two ways.

    19. A New Mechanism For Superconductivity (pages 1273–1275)

      Prof. Dr. Michael J. S. Dewar

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712731

      The interplay of two Cu-O vibrations in YBa2Cu3O7 could–at least-qualitatively–not only explain the surprisingly high critical temperature of this material but also the sensitivity of the critical temperature towards magnetic fields and 16O/18O isotopic exchange. Important is a linear arrangement of metal atoms in two oxidation states (e.g. CuII/CuIII), in'which two coordinated lattice vibrations lead to (directed) electron hopping.

    20. Superconductivity—a New Classification of the Chemical Bonding in the Solid Allows to Understand Its Occurrence (pages 1275–1277)

      Prof. Dr. Werner Urland

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712751

      The interplay of electron delocalization, localization and correlationwith about equal energy contributions is decisive for the occurrence of superconduction. As further development of the concepts of other scientists (particularly those of Wooley and Anderson) a kind of phase diagram is presented in which the solid states are classified according to the energies of the three electronic interactions EDel, ELoc and ECorr. In this way superconductors are found to be grouped in the neighborhood of the “triple point”.

    21. A Facile, General Route to Bridge-Annelated [2.2]Paracyclophanedienes (pages 1277–1278)

      Dipl.-Chem. Oliver Reiser, Stefen Reichow and Prof. Dr. Armin de Meijere

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712771

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      Heck coupling of the tetrabromoparacyclophanediene 1 with olefins yields te-traalkenyl derivatives which can be smoothly converted into bisbenzoanne-lated [2.2]paracyclophandienes by electrocyclization/dehydrogenation. The tetraphenyl derivative 2 is characterized by eight orthogonal bipheny! units; consequently, it can be expected to exhibit interesting spectroscopic properties.

    22. High-Resolution CP-MAS 13C-NMR Spectra of Allylzinc Compounds—Structural Similarities and Differences in the Solid State and in Solution (pages 1279–1280)

      Priv.-Doz. Dr. Reinhard Benn, Dipl.-Phys. Hiltrud Grondey, Prof. Dr. Herbert Lehmkuhl, Dr. Hans Nehl, Dr. Klaus Angermund and Prof. Dr. Carl Krüger

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712791

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      Whether the allyl ligand is η1- (1), η1, η2- (2) or η3-bound (3) can be ascertained by high-resolution solid-state CP-MAS 13C-NMR spectroscopy in the case of 3,3-dimethylallylzinc chloride (η1), bis(2-methylallyl)zinc (η12), bis(allyl)zinc and 2-methylallylzinc chloride (each η3). In contrast, in donor solvents the allyl groups in all four cases are bound in an η1-like fashion to zinc.

    23. Dipyrrolo [2-a:2′,l′-c]quinoxalines: A Novel Heterocyclic System (pages 1280–1281)

      Prof. Dr. Gerd Kaupp, Dipl.-Chem. Heike Voss and Dr. Herbert Frey

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712801

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      Cyclic N-oxides as partners for cycloaddition reactions: Both the mono- as well as the dioxides of quinoxalines which are methyl-substituted in the α-position to the N-atom react regioselectively with methyl phenylpropiolate with elimination of water. For example, the heterocycles 2 and 3 are formed from the oxides of 1.

    24. Regioselective Protonation of Allylic Anions (pages 1281–1282)

      Prof. Dr. Siegfried Hünig, Dipl.-Chem. Norman Klaunzer and Dipl.-Chem. Rüger Schlund

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712811

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      What influence has the proton source on the ratio of α-to γ-protonation in allyl anions? Attempts have been made to clarify this with the model compounds 1. The ratio 2a :3a varies from >99:1 (e.g. XH [DOUBLE BOND] H2O, MeOH,/BuOH) to 66:34(MeCH(CO2Et)2), the ratio 2b:3b from 95 :5 (D2O, MeOD) to 10:90 (MeCH(CO2Et2). a, aryl [BOND] Ph; b, aryl [BOND] 3,5-Cl2C6H3.

    25. Enantioselective Protonation of Carbanions with Chiral Proton Sources (pages 1283–1285)

      Dipl.-Chem. Uwe Gerlach and Prof. Dr. Siegfried Hünig

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712831

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      An α-hydroxycarboxylic acid structural unit of the chiral proton source X*H guarantees the greatest enantioselectivity in the protonation of the cyclic ester enolate 1. Amines which are formed in the synthesis of 1 with lithium amides hardly influence the selectivity of the protonation. Variation of the alkali metal and of the solvent revealed that a contaction structure of 1 is essential for high selectivities. The highest eevalues achieved are ca. 50%.

    26. 2,2-Dimethyl-4,5-dimethylene-l,3-cyclopentanediyl (pages 1285–1287)

      Prof. Dr. Wolfgang R. Roth, Dr. Udo Kowalczik, Prof. Dr. Günther Maier, Dr. Hans Peter Reisenauer, Prof. Dr. Reiner Sustmann and Dipl.-Chem. Wolfgang Müller

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712851

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      To explore the limits of Hund's rule investigations are currently carried out on so-called “disjoint diradicals” since such species reveal a discrepancy between theory and experiment. Thus, according to ESR and NMR spectroscopic findings the title compound 1 has a triplet ground state, although a singlet ground state was predicted for the planar tetramethyleneethane. 1 is accessible in four ways from 2–5.

    27. X-Ray Structure Analysis of the Li2-Compound of Bis(trimethylsilyl)metnyl Phenyl Sulfone; Structural Units of an α-Sulfonyl- and a Complex-Stabilized ortho-Sulfonyl-“Carbanion” (pages 1287–1288)

      Dipl.-Chem. Werner Hollstein, Dr. Klaus Harms, Michael Marsch and Prof. Dr. Gernot Boche

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712871

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      The formation of C-Li-O-S-C five-membered rings is the most important characteristic in the double lithiation of bis(trimethylsilyl)methyl phenyl sulfone 1 (R [DOUBLE BOND] R′ [DOUBLE BOND] H), in which 2 is formed. 2 is present as dimer in the crystal; the two monomers are coupled via Li2O2 four-membered rings. The structure in the crystal is stabilized by four ether ligands per dimer. There are no interactions between Li and the “carbanionic” C(SiMe3)2 groups. The sp2 orbital of the orthoC-atom of 2 points to the midpoint between the two Li ions.

    28. Coupling of Two Ethyne Molecules at a Nickel Center to Form a Nickelacyclopentadiene Complex (pages 1288–1290)

      Dr. Klaus-Richard Pörschke

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712881

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      The Ni-catalyzed cyclooligomerization of acetylene according to Reppeprobably proceeds stepwise via a nickelacyclopentadiene intermediate. By reaction of 1 with ethyne in excess and iPr2PCH2CH2PiPr2 in pentane at −78°C (!) it has now been possible for the first time to obtain a NiC4H4-complex via 2 and to characterize it IR and NMR spectroscopically. In the formula of 2 on the right a Ni(iPr2PCH2CH2PiPr2) unit has been omitted.

    29. The Dependence of Intramolecular Electron Transfer on Structure in a Spiro Compound Containing Two Cyclooctatetraene Moieties (pages 1290–1291)

      Dipl.-Chem. Günter Krummel, Priv.-Doz. Dr. Walter Huber and Prof. Dr. Klaus Mullen

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712901

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      The magnitude of the reorganization energy is′ decisive for the rate of intramolecular electron transfer. This has been demonstrated by investigations on the mono- and dianions of 1, in which the excess charge is in each case localized in a COT ring, since an energy of ca. 12 kcal mol-1 is required for an alternating planarization of the eight-membered rings. 1 is surprisingly easily accessible from Li2COT and C(CH2Br)4 (COT[DOUBLE BOND]cyclooctatetraene).

    30. Dibenzo[fg,mn]octalene and Cycloocta[def]phenanthrene. New Models for the Conformational Analysis of Biphenyl Systems (pages 1291–1293)

      Dipl.-Chem. Willi Heinz, Dr. Peter Langensee and Prof. Dr. Klaus Müllen

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712911

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      The angle of twist of the biphenyl unit is almost halved on going from 1 to 2. On the other hand, according to the UV spectra it should be greater in 3 than in 1. Particularly striking in the case of 3 is a symmetry lowering by charge localization in the dianion, so that an uncharged butadiene bridge can remain bent. As a result of the charge localization the central bridgehead atoms in 32e do not have the highest charge density; reaction with Me2SO4 leads exclusively to formation of 4.

    31. 1,5-EIectrocyclization in Homofuran, Homopyrrole, and Homothiophene (pages 1294–1295)

      Prof. Dr. Frank-Gerrit Klärner and Dr. Dietmar Schröer

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712941

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      The electrocyclic ring-opening l[RIGHTWARDS ARROW]2 is accelerated drastically when X[DOUBLE BOND]S: at 120°C, 1c reacts 63100 times, 1b only 72 times more rapidly than la. The isomerization 1[RIGHTWARDS ARROW]3 could be achieved only with la under vigorous conditions, from which a difference of at least 96 kJ mol-1 was deduced for the activation energies of the orbital symmetry allowed process 2a[RIGHTWARDS ARROW]1a and the forbidden process 2a[RIGHTWARDS ARROW]3a (a, X[DOUBLE BOND]O; b, X[DOUBLE BOND]ŇO2Me; c, X[DOUBLE BOND]S).

    32. Stereocontrolled Formation of Annelated Cyclopentanes by Intramolecular Hetero-Diels–Alder Reaction. Synthesis of Deoxyloganin from Citronellal (pages 1295–1297)

      Prof. Dr. Lutz F. Tietze, Dr. Horst Denzer, Dipl.-Chem. Xenia Holdgrün and Dr. Manfred Neumann

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712951

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      An astonishingly highly induced diastercoselectivity (>98%) characterizes the intermolecular cycloaddition of the adduct of 1 and 2. The cis coupled cyclopenta[c]pyran derivative 3 is formed, which could be converted in six steps into the deoxyloganin 4. Compound 4 is of interest as a precursor for the biosynthesis of alkaloids.

  3. Correspondences

    1. Top of page
    2. Reviews
    3. Communications
    4. Correspondences
    5. Corrigenda
    6. Book Reviews
    7. Author Index
    8. Subject Index
    1. Back to the Structure of Benzene (page 1298)

      Prof. Dr. R. Janoschek

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712981

  4. Corrigenda

    1. Top of page
    2. Reviews
    3. Communications
    4. Correspondences
    5. Corrigenda
    6. Book Reviews
    7. Author Index
    8. Subject Index
    1. You have free access to this content
      CORRIGENDUM (page 1298)

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198712982

  5. Book Reviews

    1. Top of page
    2. Reviews
    3. Communications
    4. Correspondences
    5. Corrigenda
    6. Book Reviews
    7. Author Index
    8. Subject Index
  6. Author Index

    1. Top of page
    2. Reviews
    3. Communications
    4. Correspondences
    5. Corrigenda
    6. Book Reviews
    7. Author Index
    8. Subject Index
  7. Subject Index

    1. Top of page
    2. Reviews
    3. Communications
    4. Correspondences
    5. Corrigenda
    6. Book Reviews
    7. Author Index
    8. Subject Index
    1. Subject Index (pages 1309–1324)

      Version of Record online: 22 DEC 2003 | DOI: 10.1002/anie.198713091

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