Step 2: Preparation of N-(2-chloro-6-fluoro-3-nitrophenyl)acetamide. Sodium nitrate (4.53 g, 53.3 mmol) was dissolved in water (5 mL) and slowly added dropwise to a stirred solution of N-(2-chloro-6-fluorophenyl)acetamide (5 g, 26.7 mmol) in concentrated sulfuric acid (10 mL). After dropwise addition, the resulting yellow solution was stirred at 0 °C for 30 min, then warmed up to room temperature and continued stirring for 12 hours. Upon completion of the reaction, the mixture was poured into water (~250 mL) and the precipitated solid was collected by vacuum filtration. The crude product was purified by recrystallization from acetonitrile to give the title compound in the form of a light brown solid (3.2 g, 49% yield). The product was characterized as follows: 1H NMR (400 MHz, DMSO-d6) δ 10.07 (s, 1H), 8.12 (dd, J = 9.2, 5.0 Hz, 1H), 7.70-7.55 (m, 1H), 2.12 (s, 3H); ESIMS m/z 233 ([M + H]+).
