2-Chloro-6-methoxy-3-nitropyridine (20.85 g, 110.57 mmol) was used as starting material and suspended in concentrated hydrochloric acid (37%, 171 mL, 5528.49 mmol). The reaction mixture was stirred at 90 °C for 3 h and subsequently cooled to room temperature. The pH of the reaction mixture was adjusted to 5 with 2 M NaOH solution, and then the aqueous phase mixture was successively extracted with ethyl acetate (EtOAc, 250 mL). The organic phases were combined and concentrated to give a yellow solid. The solid was filtered and washed with ether (Et2O, 200 mL). The solid was re-suspended in ethyl acetate (200 mL), stirred and filtered to remove the insoluble green solid. The filtrates from the two filtrations were combined, dried with anhydrous magnesium sulfate (MgSO4) and concentrated to give 6-chloro-5-nitropyridin-2-ol as a yellow solid (14.7 g, 84.22 mmol, 76% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 6.52 (1H, d), 8.26 (1H, d), no OH peak was observed. Mass spectral analysis showed m/z 173 (MH)+.
