Synthesis of benzothieno[2,3-b]thiophenes, [2,3-b:3′,2′-d]- dithienothiophenes and their selenium derivatives via electrophilic cyclization and McMurry cyclization

摘要

Benzothieno[2,3-b]thiophenes, [2,3-b:3′,2′-d]- dithienothiophenes, and their selenium derivatives were synthesized in good yields from readily available 3-ethynyllithio-benzo[b]thiophenyllithio compounds, sulfur or selenium, and 2 equiv of acid chlorides. Two heteroarene rings were constructed by a twofold cyclization via an acid chloride-induced electrophilic ring closing and the McMurry cyclization using Zn/TiCl _4 reagents.