Donor-Acceptor-Substituted Cyclic π-Electron Systems—Probes for Theories and Building Blocks for New Materials

Authors

  • Prof. Dr. Rudolf Gompper,

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    1. Institut für Organische Chemie der Universität, Karlstrasse 23, D-8000 München 2 (FRG)
    • Institut für Organische Chemie der Universität, Karlstrasse 23, D-8000 München 2 (FRG)
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  • Dr. Hans-Ulrich Wagner

    1. Institut für Organische Chemie der Universität, Karlstrasse 23, D-8000 München 2 (FRG)
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Abstract

Donor and acceptor substituents stabilize (4n)π-electron systems and destabilize those with (4n+2)π electrons. The same is true for the transition states of pericyclic reactions, which explains the appearance of dipolar intermediates in symmetry-allowed cycloadditions and sigmatropic rearrangements. Donor-acceptor-substituted semibullvalenes undergo rapid Cope rearrangement, as do tetraazabarbaralanes. In contrast, tetraazasemibullvalenes can not be isolated, since the isomeric tetrazocines always result. The usefulness of the donor-acceptor concept in preparative chemistry is demonstrated by numerous stable cyclic (4n)π-electron systems, like donor-acceptor-substituted cyclobutadienes, tetraaminobenzene, and p-benzoquinone dications, benzodiazepinyl anions, and donor-acceptor-substituted cyclopentadienyl cations and their heteroatom-containing analogues. The new compounds are of interest in the fields of organic metals and ferromagnets, nonlinear optics, and dyestuffs, among others.

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