The Reaction of 2-Amino-4,5,6,7-tetrahydrobenzo[b]thiophenes with Benzoyl-Isothiocyanate: Synthesis of Annulated Thiophene Derivatives and Their Antitumor Evaluations

The reaction of the tetrahydrobenzo[b]thiophene derivatives 1a,b with benzoylisothiocyanate (2) afforded the thiourea derivatives 3a,b. Cyclization of the latter products gave the annulated products 4a,b. Compounds 3a,b reacted with either hydrazine hydrate (5a) or phenyl hydrazine (5b) afforded compounds 7a-d which underwent cyclization for compounds 7a,c afforded compound 9. On the other hand compounds 4a,b reacted with either hydrazine hydrate (5a) or phenyl hydrazine (5b) afforded compounds 6a-d a second pathway was applied to synthesize compound 6c which underwent cyclization afforded compound 9. Also compounds 4a,b reacted with either phenacyl bromide (10) afforded compounds 11a,b or ethylchloroacetae (12) compounds 13a,b were produced. The latter products reacted with each hydrazine hydrate (5a) and phenyl hydrazine (5b) afforded compounds 14a-d. Their antitumor activities were tested using three different cell lines.