V. V. Titov

Electronic absorption spectra of pseudoazulenes — Benzo[b]cyclopenta[e]pyran derivatives

Benzo[b]cyclopenta[e]pyran derivatives were synthesized, and their electronic absorption spectra were recorded. The absorption spectra were calculated by the Pariser-Parr-Pople method. The absorption bands in the spectra of the synthesized compounds were assinged on the basis of an anlysis of the experimental and calculated values obtained in the study. It is shown that the long-wave transition in the spectra of benzo[b]cyclopenta[e]pyrans is realized through charge transfer from the five-membered ring to the six-membered heteroring and is determined to a great degree by the pronounced delocalization of the C-C bonds in the fulvene fragment on passing to the first excited state. The bathochromic shift of the long-wave band when phenyl and styryl substituents are introduced is due to the increase in the energy of the upper occupied molecular orbital as compared with the virtual invariability of the level of the lower vacant molecular orbital.

Pyrylation of 1,2-diphenylbenzo[b]cyclopenta[e]pyran

Abstract1,2-Diphenylbenzo[b]cyclopenta[e]pyran was pyrylated with 2,6-diphenylpyrylium perchlorate. The structures of the singly and doubly charged 2,6-diphenyl-4-(1,2-di-phenylbenzo[b]cyclopenta[e]-3-pyrania)pyrylium cations are confirmed by data from the electronic absorption spectra. A radical mechanism for the pyrylation is proposed on the basis of the ESR spectrum.

Structural specificity of electrophilic substitution of reaction of 2-phenylbenzo[b]cyclopenta[e]pyran

Abstract2-Phenyl- and 1,2-diphenylbenzo[b]cyclopenta[e]pyrans were subjected to formylation, nitration, and phenylsufonylation. It was shown by PMR spectroscopy that 2-phenylbenzo[b]cyclopenta[e]pyran undergoes substitution exclusively in the 1 position. The effect of the spatial orientation and the degree of electron-acceptor character of the introduced substituents on the chemical shift of the 9-H proton was studied.

New method for the synthesis of tetrathiofulvalene

A new method for the synthesis of tetrathiofulvalene is presented, and conditions for the synthesis of its complex with 7,7,8,8-tetracyanoquinonedimethane are described.