An Improved Synthesis of 4-(1-Piperazinyl)benzo[b]thiophene Dihydrochloride

2-Chloro-6-fluorobenzaldehyde was converted to 4-(1-piperazinyl)benzo[b]thiophene dihydrochloride (18), an intermediate in the synthesis of brexpiprazole, via a five-step sequence in 54% overall yield. This procedure requires no expensive catalyst and avoids the side products produced in the coupling step in the reported process. Several kilograms of compound 18 were prepared using this economical and scalable process.