Thiophosgene → 3,5-Dichloro-2-isothiocyanatopyridine

Thiophosgene (21.9 ml, 288 mmol) was added dropwise to a stirred mixture of 3,5-dichloropyridin-2-amine (23.5 g, 144 mmol) in tetrahydrofuran (150 mL) and saturated aqueous sodium hydrogen carbonate (150 mL) at 0° C., and the mixture was stirred at room temperature for 4 hr. The mixture was diluted with saturated aqueous sodium hydrogen carbonate, and extracted with ethyl acetate. The combined organic layer was washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated in vacuo. The residue was purified by flash column chromatography on silica gel eluting with a 5-30% ethyl acetate/n-hexane gradient mixture. The filtrate was concentrated in vacuo to give the title compound as a yellow solid (11.4 g, 55.6 mmol, 39%).