20.3 g of 2-chloro-6-nitrobenzoic acid, 1.2 g of cuprous oxide, 40 g of cesium carbonate, 50 g of DMF, and 85 g of 30% self-prepared ammonia solution were added to a 500 mL autoclave. The temperature was raised to 90 °C, and ammonia gas was introduced during the reaction to maintain the pressure inside the autoclave at 0.7~0.8 MPa. The reaction was carried out for 12 h. Samples were taken for control. The phases were separated, and the upper layer was collected. Hydrochloric acid was added to acidify to pH 1~2. The mixture was filtered, and the filtrate was collected. The mixture was extracted three times with diethyl ether, and the upper ether phase was collected. The solvent was removed by distillation to obtain 18.7 g of crude 2-amino-6-nitrobenzoic acid (HPLC purity: 88%), yield: 90%. Recrystallization with ethyl acetate yielded 15.5 g of 2-amino-6-nitrobenzoic acid product (HPLC purity > 97%), overall yield: 85%.
