Electrochemical Bromination of Substituted Thiophenes in Batch and Continuous Flow

An electrochemical bromination of thiophenes from ammonium bromide is developed both in batch and continuous-flow conditions. Substituted thiophenes possessing 2-hydrogens selectively afford a series of 2-bromothiophenes while 2-substituted benzothiophenes generate 3-bromobenzo[b]thiophenes. Based on the cyclic voltammetric studies and literature, a bromine cation involved mechanism was proposed.