Step 1: 3-Chloro-2-nitrobenzoic acid (30 g, 0.148 mol) was dissolved in aqueous potassium hydroxide solution (240 g, 4.277 mol in 300 mL H2O) and stirred at room temperature until completely dissolved. Subsequently, the reaction mixture was heated to 110°C and kept for 12 hours for the reaction. Upon completion of the reaction, the mixture was cooled to room temperature, diluted with water and acidified with concentrated hydrochloric acid to pH 2. The acidified mixture was cooled at 0°C and subsequently extracted with ethyl acetate (2 x 500 mL). The organic layers were combined, washed with brine solution, dried over anhydrous sodium sulfate and filtered. The filtrate was evaporated under reduced pressure to give 3-hydroxy-2-nitrobenzoic acid (27 g, 99% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 13.8 (brs, 1H), 11.21 (s, 1H), 7.47 (t, J = 8.0 Hz, 1H), 7.39 (dd, J' = 8.0 Hz, J'' = 1.6 Hz, 1H), 7.30 (dd, J'' = 7.6 Hz, J'' = 0.8 Hz. 1H); ESI-MS: calculated mass: 183.02; observed mass: 182.10 [M-H]-.
