To a solution of (2R)-2-(4-chloro-3-hydroxybenzyl)-4-benzylpiperazine (3.78 g) and triethylamine (5.71 ml) in dichloromethane was added 4-dimethylaminopyridine (0.29 g) and tert-butyldimethylsilyl chloride (5.30 g) successively with ice bath cooling under nitrogen atmosphere. After stirring overnight at room temperature, water (50 ml) was added to the mixture and the organic layer was separated, washed with brine, dried over sodium sulfate, and evaporated in vacuo. The residue was purified by column chromatography on silica gel with a mixture of dichloromethane and methanol (10:1) as eluent to give (2R)-4-benzyl-2-[4-chloro-3-(tert-butyldimethylsilyloxy)benzyl]piperazine (4.11 g) as an oil.
