General procedure for the synthesis of 3-amino-5-bromo-1-methyl-3-nitropyridin-2(1H)-one from 5-bromo-1-methyl-3-nitropyridin-2(1H)-one: To a 1-liter three-necked round-bottomed flask fitted with a mechanical stirrer and a reflux condenser, under nitrogen protection, was added 5-bromo-1-methyl-3-nitropyridin-2(1H)-one (21.7 g, 93.3 mmol) , ethanol (305 mL), iron powder (-325 mesh, 52.1 g, 933 mmol) and 2N hydrochloric acid (50 mL, 100 mmol). The reaction mixture was heated and stirred at 60°C for 2 hours. After completion of the reaction, it was cooled to room temperature and the pH was adjusted to 8 (measured by pH paper) by adding potassium carbonate. The resulting suspension was filtered and the filter cake was washed with ethanol (4 x 100 mL). The filtrates were combined and concentrated under reduced pressure to give a brown solid. The solid was purified by silica gel column chromatography to afford the target product 3-amino-5-bromo-1-methylpyridin-2(1H)-one (14.5 g, 77% yield) as an off-white powder with a melting point of 104-105 °C. 1H NMR (500 MHz, DMSO-d6) δ 7.15 (d, 1H, J = 2.5 Hz), 6.46 (d, 1H, J = 2.5 Hz), 5.45 (bs, 2H), 3.40 (s, 3H); MS (ESI+) m/z 203 (M+H).
