Abstract The title compound 6 has been synthesized and the effect of cyclic π-system insertion into diphenylcyclopropenone 1 has been discussed. The distribution of positive charge over the 3-membd. ring and phenyl groups slightly predominates in 6 than in parent annulenone 1, in contrast to 5-cycloheptatrienylidene-2 (5H)-thiophenone 5 whose 7- membd. ring is more olefinic than parent tropone 2. Electronic spectrum of 6 exhibits a ...