Studies in sulfur heterocycles. Part 16. Use of 7-hydroxy-1-benzothiophenein the synthesis of substituted benzothiophene derivatives and tricyclic compounds incorporating a fused thiophene ring

Heteroatom directed ortho-metallation on N,N-diethyl-7-carbamoyloxy-1-benzo thiophene, readily available from 7-hydroxy-1-benzothiophene enabled regios elective substitution in the 6-position. Both 7- and 4-hydroxy-1-benzothiop hene were used in the annelation of 5- or 6-membered oxygen heterocycles on to the 1-benzothiophene molecule through sequential Claisen rearrangement-r ing closure reactions. The nature of the annelated ring depends upon the re action conditions.