Oxidant- and Catalyst-Free Synthesis of Sulfonated Benzothiophenes via Electrooxidative Tandem Cyclization.

A green and practical electrochemical method for the synthesis of C-3-sulfonated benzothiophenes from 2-alkynylthioanisoles and sodium sulfinates was developed under oxidant- and catalyst-free conditions. Moderate to good yields of sulfonated benzothiophenes bearing important and useful functional groups have been achieved at a constant current. Preliminary mechanistic studies indicated a tandem radical addition-cyclization pathway. Moreover, the protocol is easy to scale up and exhibits good reaction efficiency.