A mixture of (S)-2-(4-bromophenyl)-1,4-di(t-butoxycarbonyl)piperazine (1.82 g, 4.11 mmol), 4-methoxyphenylboronic acid (937 mg, 6.17 mmol), sodium carbonate (2.18 g, 20.6 mmol), and tetrakis(triphenylphosphine)palladium(0) (238 mg, 0.206 mmol) was dissolved in dimethoxyethane (20 mL) and water (20 mL), and the resulting solution was refluxed for 3 h. After cooling to room temperature, the mixture was partitioned between ethyl acetate and water. The organic layer was washed with brine, dried over anhydrous sodium sulfate, and concentrated in vacuo. The resulting solid was washed with ethyl acetate to afford (S)-1,4-di(t-butoxycarbonyl)-2-(4′-methoxybiphen-4-yl)piperazine (1.46 g, 75.9%) as a white solid.
