21427-61-2

1072-98-6

21427-61-2

Preparation of Example A2 5-chloro-2-hydroxy-3-nitropyridine (STR9): 321 g of 2-amino-5-chloropyridine was slowly added dropwise to 1.25 L of concentrated sulfuric acid with continuous stirring until the raw material was completely dissolved. Subsequently, 172.5 g of sodium nitrite (dissolved in 240 mL of water) was slowly added at 40°C to 45°C and the reaction mixture continued to be stirred for 15 minutes. Next, 125 mL of pure nitric acid was slowly added dropwise over 40 minutes at 50°C. The reaction mixture was maintained at 55°C for 1 hour and then the reaction was quenched by pouring into 5 kg of ice water. The yellow precipitated product was collected by filtration, washed thoroughly with deionized water and dried at 60°C to afford 351 g of 5-chloro-2-hydroxy-3-nitropyridine in 80.5% of the theoretical yield and a melting point of 229°C to 231°C.