General procedure for the synthesis of 2,3,6-trichloro-5-nitropyridine from 2,3,6-trichloropyridine: 2,3,6-trichloropyridine (62 mmol, 11.27 g) was dissolved in a mixture of fuming nitric acid (62 mL) and concentrated sulfuric acid (50 mL), and the reaction was heated for 12 hours at 100 °C. Upon completion of the reaction, the mixture was cooled to room temperature and carefully poured into an ice/water mixture. Subsequently, extraction was carried out with dichloromethane. The organic phases were combined, dried with anhydrous magnesium sulfate and concentrated under reduced pressure to remove the solvent to afford 2,3,6-trichloro-5-nitropyridine as a light green oil, which solidified on standing (9.65 g, 68% yield).
