A solution of (2S)-2-(4-bromophenyl)-piperazine-1,4-dicarboxylic acid di-tert-butyl ester (1.06 g, 2.40 mmol), piperidine (0.29 ml, 2.88 mmol), palladium acetate (22.0 mg, 0.096 mmol), sodium tert-butoxide (323 mg, 3.36 mmol) and 2-(di-t-butylphosphino)biphenyl (57.0 mg, 0.192 mmol) in toluene (16 ml) was stirred at 80° C. for 6 hours. Water and ethyl acetate were added to the solution and the solution was passed through Celite column. The whole was extracted with ethyl acetate and the organic lawyer was washed with brine, dried over anhydrous sodium sulfate and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (hexane/ethyl acetate) to give (2S)-2-(4-piperidin-1-yl-phenyl)-piperazine-1,4-dicarboxylic acid di-tert-butyl ester (455 mg, 43%) as white crystals.
