General procedure for the synthesis of 2,4-dichloro-5-(chloromethyl)-pyridine from (4,6-dichloropyridin-3-yl)methanol: To a stirred solution of (4,6-dichloropyridin-3-yl)methanol (2.5 g, 14 mmol) in dichloromethane (20 mL) was slowly added thionyl chloride (1.2 mL, 14 mmol) at room temperature. The reaction mixture was stirred for 15 min, then cooled to 0 °C and washed with saturated aqueous sodium bicarbonate. The organic phase was dried with anhydrous magnesium sulfate, concentrated under reduced pressure, and purified by rapid chromatography on silica gel (eluent: dichloromethane) to afford 2,4-dichloro-5-(chloromethyl)-pyridine (1.3 g, 47% yield).
