4-(4-Nitro-2-trifluoromethyl-benzenesulfonyl)-piperazine-1-carboxylic acid benzyl ester (0.5 g, 1.0 mmol) was suspended in a 5:1 mixture of ethanol and water (20 ml). To this solution was added iron powder (0.16 g, 2.6 mmol) followed by saturated ammonium chloride solution (1 ml) and the mixture was heated to 80° C. for three hours. After this time, the reaction mixture was cooled to room temperature and filtered through a pad of celite, the celite was washed with ethanol (10 ml) and ethyl acetate (50 ml) and the solution was concentrated under vacuum. The resulting residue was partitioned between DCM (50 ml) and water (20 ml), the organic layer was separated, dried with MgSO4, filtered and concentrated to afford the title compound (0.44 g, 94% yield) as a yellow solid. Tr=2.03 min, m/z (ES+) (M+H)+ 444.
