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  • 1985-1989  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Synthese von Pentafulvalen durch oxidative Kupplung von Cyclopentadienid mittels Kupfer(II)-chlorid50. Mitteilung über Fulvene, Fulvalene; 49. Mitteilung: [1]; Kurzmitteilung: [2]. (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 1644-1654 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Pentafulvalene by Oxidative Coupling of Cyclopentadienide with Copper(II) ChlorideStarting with a nearly quantitative coupling of cyclononatetraenide 7 to 1, 1′-dihydrononafulvalene 8 by means of AgBF4, a simple general synthetic concept for fulvalenes is outlined (Scheme 2), consisting in an oxidative coupling of ‘Hückel anions’ like 2 and 7 to 1, 1′-dihydrofulvalenes 10 with Ag(I) or Cu(II) salts, followed by deprotonation (→11) and oxidation (→12); it has been realised in the case of pentafulvalene (1; overall yield 61%; Scheme 3) and 1,2:5,6-dibenzopentafulvalene (18; overall yield 66%, Scheme 4). NMR-spectroscopic investigations show that 1 is a non-aromatic compound with strongly alternating bond-lengths, its π-system being even more localised than that of simple pentafulvenes. In fact, 1 is extremely reactive in concentrated solutions above -50°. Besides of polymerisations, Diels-Alder dimerisation 1→19 followed by a rearrangement 19→20 takes place (Scheme 5).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19860690719
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  • 2
    Electronic Resource
    Electronic Resource
    Nonapentafulvalen51. Mitteilung über Fulvene, Fulvalene; 50. Mitteilung: [1]; Kurzmitteilung: [2].Teil der Dissertation von A.E. [3]. (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 49-58 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nonapentafulvalene(1) has been prepared by oxidative coupling of sodium cyclopentadienide (6) and sodium cyclononatetraenide (7) with CuCl2 in THF, two-fold deprotonation of cyclopentadienyl-cyclononatetraene 8 to give dianion 16, and oxidative treatment of 16 with CuCl2 (Schemes 2 and 3). Compound 1 is a highly reactive and thermally instable molecule, since valence isomerisation 1 → 17 proceeds easily even at low temperature (the half-life of 1 is ca. 30 min at -15° in CDCl3). NMR investigations show that nonapentafulvalene is an olefinic molecule with strongly alternating bond lengths, its nine-membered ring deviating strongly from planarity. Comparison of the NMR data of 1 with those of a series of sterically similar pentafulvenes 18 and nonafulvenes 19 (Tables 1 and 2) demonstrates that (a) with regard to the pentafulvene unit of 1, the cyclononatetraene ring acts as very weak electron-donating group, while (b) with regard to the nonafulvene unit of 1, the cyclopentadiene ring acts as weak electron-accepting group. So nonapentafulvalene may be regarded as a ‘nonafulvene of inverse π-polarisation’.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700106
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  • 3
    Electronic Resource
    Electronic Resource
    Nonafulvalen: Synthese durch oxidative Kupplung von Cyclononatetraenid und Valenzisomerisierung53. Mitt. über Fulvene, Fulvalene; 52. Mitt. [1]; Kurzmitt. [2]. (1987)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 70 (1987), S. 1623-1637 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nonafulvalene: Synthesis by Oxidative Coupling of Cyclononatetraenide and Valence IsomerisationFollowing a general strategy (Scheme 2) for the synthesis of fulvalenes by oxidative coupling of Hückel anions, the synthesis of nonafulvalene (1), has been realised (Scheme 3). The most tricky step is a twofold deprotonation of bi(cyclononatetraenydl) 3 with K(t-BuO) to give 4; it is only possible after equilibration 3⇄3a; otherwise, deprotonation of one cyclononatetraene unit of 3 followed by oxidative coupling with AgBF4 gives quater(cyclononatetraenyl) 12 as an isomeric mixture. The reaction of 3 with Kgives potassium cct-cyclononatetraenide 11 (M = K; Scheme 5) and not the dianion 4 as reported in the literature. Nonafulvalene (1)is extremely reactive due to its very easy valence isomerisation to geve an isomeric mixture of tetrahydro-dibenzopentafulvalenes 13 (Scheme 4). The structure of crystalline isomer (E-anti)-13 has been proved by X-ray analysis.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19870700620
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  • 4
    Electronic Resource
    Electronic Resource
    1H and 13C NMR spectra of pentafulvalene compared with selected pentafulvenesFulvenes, Fulvalenes, Part 45. For Part 44, see Ref. 1. (1986)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 24 (1986), S. 350-352 
    Details
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H NMR spectrum of pentafulvalene has been analysed. Proton-proton coupling constants and 13C chemical shifts are compared with those of sterically similar pentafulvenes. Pentafulvalene can be regarded as a pentafulvene with a highly localized π-system.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260240415
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