4-Azido-2-methyl-6-nitroquinoline (CAS:1528735-22-9; 29.9 g, 130 mmol) was used as starting material and suspended in THF (450 mL). Subsequently, triphenylphosphine (41.1 g, 160 mmol) was added to the suspension and the resulting mixture was stirred at room temperature for 20 min. Next, water (45 mL) was added and the reaction solution was concentrated to about 200 mL. The concentrated solution was poured into 2.5 M aqueous HCl (1.5 L) and stirred vigorously until the solid was completely dissolved. The aqueous phase was extracted with ether (250 mL x 3), followed by adjusting the pH of the aqueous phase with 50% NaOH aqueous solution to 9. The resulting bright yellow crystalline solid was collected by filtration, washed with cold water (500 mL), and dried to give 2-methyl-6-nitroquinolin-4-amine (25.2 g, 95% yield) as a bright yellow crystalline solid: melting point >250 °C; TLC Rf 0.37 ( Spreading agent ratio 95:4.5:0.5 CHCl3:MeOH:aqueous solution, MeNH2); 1H-NMR (DMSO-d6) δ 9.22 (d, 1H), 8.25 (dd, 1H), 7.77 (d, 1H), 7.30 (s, br, 2H), 6.55 (s, 1H), 2.45 (s, 3H).
