New construction of p-tolylsulfony-substituted naphthalenes by thermal and photochemical cyclization of 1-aryl-4-(methylthio)-2-(p-tolylsulfonyl)-1,3-butadienes

Transformation of 4-(methylithio)-1-phenyl-2- (p-tolylsulfonyl)-1, 3-butadiene 1a was found to give 2- (p-tolylsulfonyl)naphthalene 3a either by the action of I-2 in refluxing acetonitrile or by irradiation with a high-pressure Hg lamp. An electron-withdrawing group (p-F or p-CO2Me) on the phenyl ring retarded the thermal reaction, but the corresponding naphthalene derivative was efficiently produced by the photolysis in the presence of I-2. The substituent effect of an electron-donating methoxyl group is also reported (C) 2001 John Wiley & Sons, Inc.