A solution of the mixture of 2-bromo-4-phenylthiophene and 2-bromo-3-phenylthiophene (6.00 g, 25.0 mmol), 1-ethoxycarbonylpiperazine (3.96 g, 25.0 mmol), sodium tert-butoxide (3.48 g, 36.2 mmol), 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (468 mg, 0.750 mmol) and tris(dibenzylideneacetone)dipalladium (0) (544 mg, 0.594 mmol) in toluene (50 ml) was stirred at 100° C. for 48 hours. Insolubles were filtered off and the filtrate was concentrated. The residue was purified by silica gel column chromatography (hexane:ethyl acetate=9:1) to obtain ethyl 4-(4-phenyl-2-thienyl)piperazine-1-carboxylate (365 mg, 4.61%) as an oil.
