Sulfuryl chloride → Ethyl 3-chloro-2-oxopiperidine-3-carboxylate

To a mixture of ethyl 2-oxopiperidine-3-carboxylate (30 g) in THF (300 mL) was added dropwise sulfuryl chloride (14.2 mL) at 0° C.-5° C., and the mixture was stirred at room temperature for 18 hr. To the reaction mixture was added saturated aqueous sodium hydrogen carbonate solution (300 mL) at 0° C., and the mixture was stirred at room temperature for 30 min and extracted with ethyl acetate (300 mL×3). The extract was washed with saturated brine (300 mL), and dried over anhydrous magnesium sulfate, and the solvent was evaporated under reduced pressure. The residue was washed with hexane/ethyl acetate (5/1, 60 mL×2) to give the title compound (32.7 g). MS (ESI+): [M+H]+ 206.1.