PARTIALLY BENZOANELLATED CENTROHEXAQUINANES - OXIDATIVE-DEGRADATION OF CENTROPOLYINDANES BY USING RUTHENIUM(VIII) OXIDE AND OZONE

The oxidative degradation of benzo nuclei of various higher centropoly indanes with ruthenium(VIII) oxide or ozone was studied to further exp lore the chemistry of partially benzo-anellated centrohexaquinanes. Be sides the two tribenzotriquinacenes 12 and 15 which were used as model substrates for oxidation with Ru-VIII, centrohexaindane 1 was convert ed to the corresponding centrohexacyclic diketone 19 by using either R uO4 in stoichiometric amounts or O-3 in dichloromethane/pyridine. Subs equent Wolff-Kishner reduction of 19 gave pentabenzohexaquinane 4. Cor respondingly, 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 s equence). Due to the low efficiency of the ozonolyses, the parent cent rohexaquinane 3 has remained elusive, yet. The deeply red centrohexacy clic 1,2-diketone 19 was subjected to single-crystal X-ray structural analysis and found to bear an almost perfectly syn-coplanar alpha-dica rbonyl chromophore with a strong and extremely low-energy UV/Vis absor ption (lambda(max) = 512 and 531 nm).