Photoreactions of halogeno-1,4-naphthoquinones with electron-rich alkenes

Abstract

Photochemical reactions of 2,3-dichloro-1,4-naphthoquinone with 1,1-diarylethylenes or the related electron-rich alkenes have been investigated by steady-state photoreactions, flash photolysis, and kinetic analyses based on the Stern-Volmer experiment and concentration dependence of quantum yields; there is reasonable agreement between them. In acetonitrile a radical ion pair composed of a quinone radical anion and a 1,1-diarylethylene radical cation was observed, while no intermediate was observed in benzene. Dimerization products derived from radical cations were obtained only in the photoreaction of quinone with 1,1-bis(4-methoxyphenyl)ethylene.