The new substituted cyclohexane-and cyclohexene-1, 3-diones 3-6 and 9, 10, respectively, have been synthesized from tetraacetylethylene 1, through a ring expansion of the cyclopentenone 2. The structures of these products, as well as some features of their tautomeric behavior, were established on the basis of chemical properties and spectroscopic data.
