The S-MOM-protecting strategy could be applicable for other thienoacenes such as DBTDT (Scheme 4). When non-protected substrate 9a was subjected to electrolysis, DBTDT (10) was obtained in only 33% yield because polymerization of 9a competed with the desired reaction. In contrast, electrolysis of MOM-protected substrate 9b suppressed polymerization and 10 was obtained in 72% yield under similar conditions and in 82% yield under the further optimized conditions. Use of the S-MOM group is very effective for the type of organic electroorganic reactions that yield the target product by double-cyclization. In conclusion, we have developed a facile method for synthesizing BTBT derivatives by electrochemical double C-S cyclization using n Bu4NBr as a halogen mediator. The MOM group was an efficient protecting group for the sequential transformation, which enables the formation of multiple C-S bonds in one step. A variety of symmetric and asymmetric BTBT derivatives were synthesized by the method, and more πexpanded DBTDT can also be synthesized from the appropriate MOM-protected precursor. Further studies on the application of this strategy are ongoing in our laboratory.