Photolysis of 1-phenylbenzo[b]thiophenium salts was conducted by use of a Pyrex-filtered high-pressure Hg lamp. The major products in most cases were the phenyl-migrated ones, i.e., 2-phenylbenzo[b]thiophenes and 3-phenylbenzo[b]thiophenes, together with the dephenylated benzo[b]thiophenes. This photochemical behavior is quite different from the thermal ones that provide the ring-opened olefins. The
Photolysis of β-[(o-arylthio)phenyl]vinyl bromides, in contrast to the oxy-derivatives, resulted in exclusive cyclization at sulfur to give 1-benzothiophenes. The results were discussed by the nature of sulfur.