4-Methyl-3-nitroquinoline (500 mg, 2.66 mmol) was used as raw material, which was dissolved in concentrated hydrochloric acid (10 mL) and heated to 50 °C. Subsequently, tin(II) chloride dihydrate (1.5 g, 6.6 mmol) was added to the reaction system. The reaction temperature was maintained at 50 °C with continuous stirring overnight. Upon completion of the reaction, the reaction mixture was diluted with water (20 mL) and the pH was adjusted to 9 with 5 N aqueous sodium hydroxide solution. the mixture was cooled to 4 °C and extracted twice with ethyl acetate (30 mL). The organic phases were combined, washed with ice-cold water (40 mL), dried over anhydrous Na2SO4, filtered and concentrated to give 3-amino-4-methylquinoline (340 mg, 80% yield) as a yellow solid. The product was characterized by 1H NMR (400 MHz, CDCl3): δ 8.42 (s, 1H), 7.89-7.91 (m, 1H), 7.79-7.82 (m, 1H), 7.44-7.38 (m, 2H), 3.77 (br s, 2H), 2.37 (s, 3H).
