PUB - Publikationen an der Universität Bielefeld

The oxidative degradation of benzo nuclei of various higher centropolyindanes with ruthenium(VIII) oxide or ozone was studied to further explore the chemistry of partially benzo-anellated centrohexaquinanes. Besides the two tribenzotriquinacenes 12 and 15 which were used as model substrates for oxidation with Ru-VIII, centrohexaindane 1 was converted to the corresponding centrohexacyclic diketone 19 by using either RuO4 in stoichiometric amounts or O-3 in dichloromethane/pyridine. Subsequent Wolff-Kishner reduction of 19 gave pentabenzohexaquinane 4. Correspondingly, tribenzo-centrohexaquinane 2 was degraded by sequential ozonolysis/reduction to the C-2v-symmetrical dibenzocentrohexaquinane and 10 and monobenzocentrohexaquinane 11 in low yields (8-9% in each sequence). Due to the low efficiency of the ozonolyses, the parent centrohexaquinane 3 has remained elusive, yet. The deeply red centrohexacyclic 1,2-diketone 19 was subjected to single-crystal X-ray structural analysis and found to bear an almost perfectly syn-coplanar alpha-dicarbonyl chromophore with a strong and extremely low-energy UV/Vis absorption (lambda(max) = 512 and 531 nm).