General procedure for the synthesis of 1-(4-amino-2-chlorophenyl)-4-methylpiperazine from 1-(2-chloro-4-nitrophenyl)-4-methylpiperazine: 1-(2-chloro-4-nitrophenyl)-4-methylpiperazine (13.5 g, 52.8 mmol) was dissolved in methanol (200 mL) and platinum(IV) oxide (0.120 g, 0.528 mmol) was added as catalyst. The reaction system was evacuated and replaced twice with hydrogen, and then the reaction was stirred under hydrogen atmosphere for 48 hours. After completion of the reaction, the crude reaction mixture was filtered through a diatomaceous earth pad and the filter cake was washed with methanol. The filtrate was concentrated to give 1-(4-amino-2-chlorophenyl)-4-methylpiperazine as an orange solid (12 g, 100% yield). The product was characterized by 1H NMR (400 MHz, methanol-d4): δ 2.35 (s, 3H), 2.62 (br.s., 4H), 2.95 (br.s., 4H), 6.63 (dd, J = 8.53, 2.76 Hz, 1H), 6.75-6.81 (m, 1H), 6.90-6.97 (m, 1H); the mass spectra (MS ) showed m/z 226 ([M+H]+).
