PHENYL MIGRATION TO THIOPHENE RING IN PHOTOLYSIS OF 1-PHENYLBENZO[B]THIOPHENIUM SALTS

Photolysis of 1-phenylbenzo[b]thiophenium salts was conducted by use o f a Pyrex-filtered high-pressure Hg lamp. The major products in most c ases were the phenyl-migrated ones, i.e., 2-phenylbenzo[b]thiophenes a nd 3-phenylbenzo[b]thiophenes, together with the dephenylated benzo[b] thiophenes. This photochemical behavior is quite different from the th ermal ones that provide the ring-opened olefins. The selective phenyl migration to the thiophene ring and the absence of the ionic products rue characteristic of benzothiophenium systems. (C) 1997 Elsevier Scie nce Ltd.