At 0°C, 2,6-dichloro-5-fluoropyridine-3-carboxylic acid (5 g, 23.8 mmol) was dissolved in methanol (50 ml) and thionyl chloride (5.66 g, 47.62 mmol) and 2 drops of DMF were added slowly [vigorous bulging was observed]. The reaction mixture was stirred at room temperature for 3 hours. Subsequently, methanol was added to the reaction system and stirring was continued for 2 hours at room temperature. Upon completion of the reaction, the mixture was concentrated under reduced pressure and the residue was poured into ice-cold water (20 mL) and extracted with dichloromethane (2 x 50 mL). The organic layers were combined, washed sequentially with water and brine, and the solvent was evaporated under reduced pressure to afford methyl 2,6-dichloro-5-fluoropyridine-3-carboxylate (5 g, 93.8% yield).
