Synthesis of theThieno[3,2-b]thiophene and Thieno[3,2-b]furan Bare Ring Systems

Abstract

Reported here is an optimized synthesis of thieno[3,2-b]thiophene as well as the first synthetic route to thieno[3,2-b]furan. The Li-Br exchange of 3-bromothiophene with t-BuLi followed by quenching with 1,2-bis(2,2-diethoxy­ethyl)disulfide afforded 1 in 94% yield. Then, treatment of 1 with a sulfonic acid resin gave the thieno[3,2-b]thiophene 2 in 71% yield. After optimization of the conditions utilizing the same method in THF thieno[3,2-b]furan 4 was synthesized from 3 in 32% yield.