Hydrochloric Acid → (2S)-2-(4-Bromophenyl)piperazine

Hydrogen chloride in ethyl acetate solution (4N) was added to a solution of di-tert-butyl (2S)-2-(4-bromophenyl)piperazine-1,4-dicarboxylate (10 g, 22.7 mmol) in methanol (50 ml). The mixture was stirred for one hour at room temperature and the solvent was evaporated under reduced pressure to give white solid. The mixture was partitioned between saturated aqueous sodium bicarbonate and chloroform. The organic layer was washed with brine, dried over magnesium sulfate and concentrated in vacuo to afford (2S)-2-(4-bromophenyl)piperazine as white crystals. Benzylbromide (9.7 g, 56.7 mmol) was added to a solution of sodium hydride (60% in oil, 2.0 g, 50 mmol) and (2S)-2-(4-bromophenyl)piperazine in tetrahydrofuran (50 ml) at room temperature and the mixture was stirred for one hour. The mixture was partitioned between water and chloroform. The organic layer was washed with brine, dried over magnesium sulfate and concentrated in vacuo. The residue was purified by silica gel column chromatography eluting 5-10% methanol in chloroform to furnish (2S)-1,4-Dibenzyl-2-(4-bromophenyl)piperazine (6.1 g, 64%) as a colorless oil.