Synthesis of polyfunctionalized thiophenes and enediynes via ring-opening reactions of 3-lithiated thieno[2,3-b](and [3,2-b])thiophenes, 3,4-dilithiated thieno[2,3-b]thiophenes and 3,6-dilithiated thieno[3,2-b]thiophenes

Abstract

Solutions of the title lithiated thienothiophenes were synthesized from 2,5-disubstituted 3,4-dibromothieno[2,3-b]thiophenes or 3,6-dibromothieno[3,2-b]thiophenes via Br → Li exchange with 1.0 or 2.0 equiv. of BuLi (THF, –78 °C), respectively, and gave either polyfunctionalized thiophenes or polyfunctionalized enediynes (by a novel tandem ring-opening process in these cases) on being allowed to warm up to ambient temperature.