New Synthetic Approaches to the Seven-Membered Oxocarbon

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Monocyclic oxocarbon dianions C_nO_n^<2-> ( n=3-6 ) have been expressed to be symmetric D_<nh> structures from the results of a study of vibrational spectra. The higher homologue C_7O_7^<2->, however, is an unknown species. The main purpose in this research project was the synthesis of C_7O_7^<2-> species and intensive efforts were focussed on 1) introductions of oxygenated functional groups to the seven-membered ring and 2) their effective oxidations to polyketonic species.In the process, although the synthesis of C_7O_7^<2-> species has not succeeded yet, following intriguing results were disclosed; they were a) preparations of polyacetoxy- and polyhydroxytropones by solvolytic reaction conditions, b) mechanistic evidences for an acetotropy in 2-acetoxytropones, c) an estimation of oxidation potentials of functionalyzed p-tropoquinones, d) preparations of tropoquinone acetals by anodic oxidations, and e) the conformational analysis and photorearrangements of 4,4,5,5-tetramethoxycyclohepta-2,6-dienones.