Cyclic cross-conjugated hydrocarbons having inserted p-quinoid ring-I. Diphenyl-p-tropylphenylmethyl cation formed on an attempted preparation of 1-cycloheptatrienylidene-4-diphenylmethylidene-2,5-cyclohexadiene

Article abstract of DOI:10.1016/S0040-4020(01)97357-0

In connection with the synthetic studies of the cross-conjugated system 2, p-(diphenylhydroxymethyl)phenyltropolidene (13)* was prepared. On treatment with CF₃COOH, 13 transformed to an aryltropylium ion (15) via an unstable blue colored compound. Based on NMR spectroscopy and some chemical properties the structure of the pigment is assumed to be diphenyl-p-tropylphenylmethyl cation (16) rather than the primarily anticipated cross-conjugated hydrocarbon 9,9-diphenyl[1.6.7]quinarene (6).