Step A: 2-amino-4-fluorobenzoic acid (4.0 g, 25.8 mmol) was dissolved in degassed DMF (50 mL) under nitrogen protection. HOBt (4.19 g, 31 mmol), DIEA (5.4 mL, 31 mmol), EDCI (5.94 g, 31 mmol), and a methanol solution of 2N ammonia (18 mL, 36.1 mmol) were added sequentially. The reaction mixture was stirred at room temperature for 48 hours. After completion of the reaction, the reaction solution was concentrated under reduced pressure. The residue was purified by silica gel column chromatography to afford 2-amino-4-fluorobenzamide as a white solid (2.89 g, 66% yield).1H NMR (300 MHz, DMSO-d6) δ 6.28 (m, 1H), 6.44 (m, 1H), 6.90 (br s, 2H), 7.08 (m, 1H), 7.58 (m, 1H), and 7.71 (br d, 1H).
