2-Hydroxy-5-nitropyridine (200 g, 1.42 mol) was added in batches to 800 mL of concentrated hydrochloric acid under constant stirring and subsequently heated to 50 °C. Aqueous sodium chlorate solution (80.0 g, 0.75 mol dissolved in an appropriate amount of water) was added slowly and dropwise. The reaction temperature was maintained at 50 °C with continued stirring for 1 h. The reaction was cooled to 0 °C upon completion. The precipitated solid product was collected by filtration, washed thoroughly with cold water and dried to give 2-hydroxy-3-chloro-5-nitropyridine. Yield: 240 g, 1.37 mol (96.0% yield). Melting point: 195-197 °C. 1H NMR (300 MHz, DMSO-d6): δ 8.65 (d, 1H, J = 2.5 Hz), 8.36 (d, 1H, J = 2.5 Hz). 13C NMR (300 MHz, DMSO-d6): δ 153.40, 144.29, 143.59, 135.08. 130.44. mass spectrum (ES): m/z 175 ([M + H]+).
