4-Chlorobenzenesulfonyl chloride → (3R)-1-[(4-chlorophenyl)sulfonyl]-3-methylpiperazine

To a solution of 1,1-dimethylethyl (2R)-2-methyl-1-piperazinecarboxylate (1.5 g, 07.5 mmol) in dry DCM (40 mL) was added triethylamine (2.59 mL, 18.8 mmol) and 4-chlorobenzenesulfonyl chloride (3.15 g, 10.5 mmol) and the reaction stirred at room temperature for 48 h. To the reaction was added resin supported-triamine (5 g) and the mixture stirred for 4 h. The reaction mixture was filtered and the filtrate washed with 0.5 M HCl (aq., 100 mL) followed by water (100 mL) before it was dried (MgSO4), filtered and the solvent removed in vacuo. The crude product was dissolved in DCM (40 mL) and TFA (10 mL) was added. The solution was stirred for 20 min. The solvent was evaporated and the residue tajen up in DCM (40 mL) and washed with 50% aqueous sodium bicarbonate (100 mL) followed by water (100 mL). The organic phase was dried (MgSO4), filtered and the solvent removed in vacuo to give the title compound (1.62 g).