The general procedure for the synthesis of 2,3,6-trichloropyridine from 2,6-dichloropyridine was as follows: 2,6-dichloropyridine 1480.0 g and anhydrous FeCl3 89.2 g were accurately weighed, mixed thoroughly and transferred to a 2000 mL four-neck flask. The reaction mixture was heated to 100-120 °C and then chlorine gas was slowly introduced until the reaction was complete. Upon completion of the reaction, the system was cooled to 100 °C and subsequently subjected to decompression distillation. Fractions with boiling points of 118-124°C were collected as products at a pressure of -12.8 MPa. The low concentration of distillate produced during the distillation process can be recycled for the next batch of reaction. Eventually, 1715.0 g of 2,3,6-trichloropyridine was obtained by recycling the distillate in 94.0% yield, and the purity of the product was in accordance with the requirements.
