In a two neck round bottom flask (3S,5R)-3,5-dimethyl-1-(naphthalen-2-yl-sulfonyl)piperazine (100 mg, 0.33 moles) was dissolved in 25 mL of acetonitrile. K2CO3 (71 mg, 0.53 moles) was added to the reaction flask at room temperature under nitrogen atmosphere and allowed the reaction mixture to stir for about 10 min. The flask was then cooled to 0° C. and phenoxy acetyl chloride (83 μl, 0.49 moles) was added to the reaction flask drop wise at the same temperature. After addition, the reaction mixture was slowly warmed to room temperature and allowed it to stir for 3 hr. TLC indicated complete consumption of the starting material. The reaction was quenched with cold water (25 mL) and extracted with ethyl acetate (2×25 mL). The combined organic phase was washed with brine solution and dried over sodium sulphate. Solvent was removed under reduced pressure to give crude material which was purified by column chromatography (20% ethyl acetate and hexane) to afford the title compound with 98% purity.
