tert-Butyl piperazine-1-carboxylate → Tert-butyl 4-[(6-bromo-2-naphthyl)sulfonyl]piperazinecarboxylate

To a mixture of 1-tert-butoxycarbonylpiperazine (1.25 g), sodium hydrogen carbonate solution (10 ml) and ethyl acetate (10 ml), was added 6-bromonaphthalene-2-sulfonylchloride (2.05 g), and the mixture was stirred at room temperature for 1 hour and extracted with dichloromethane. The extract was washed with water, dried and concentrated. The residue was crystallized with diisopropylether to give 1-(tert-butoxycarbonyl)-4-(6-bromonaphthalene-2-sulfonyl)piperazine as colorless crystals (2.83 g).