The general procedure for the synthesis of 2,6-dibromo-3-methoxy-5-nitropyridine using 2,6-dibromo-3-methoxypyridine as starting material was as follows: first, concentrated sulfuric acid (16 mL) was slowly added to the reaction vessel at 0 °C. Subsequently, 2,6-dibromo-3-methoxypyridine (3.4 g, 13 mmol) was added in batches, and the process was completed within 20 min. Next, 90% fuming nitric acid (16 mL, 318 mmol) was added dropwise to the reaction system. After installing a reflux condenser, the reaction mixture was gradually warmed to room temperature, then heated to 65 °C and maintained at this temperature for 2 hours. Upon completion of the reaction, the mixture was slowly poured into a 500 mL beaker containing ice. After the ice was completely melted, the mixture was vacuum filtered and the resulting solid was washed with a small amount of cold water. Finally, the collected solid was dried under vacuum to afford the target product 2,6-dibromo-3-methoxy-5-nitropyridine (1.67 g, 5.4 mmol) in 42% yield as a light yellow solid.
