Studies in sulfur heterocycles. Part 16. Use of 7-hydroxy-1-benzothiophene in 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-benzothiophene, readily available from 7-hydroxy-1-benzothiophene enabled regioselective substitution in the 6-position. Both 7- and 4-hydroxy-1-benzothiophene were used in the annelation of 5- or 6-membered oxygen heterocycles onto the 1-benzothiophene molecule through sequential Claisen rearrangement–ring closure reactions. The nature of the annelated ring depends upon the reaction conditions.