The general procedure for the synthesis of tert-butyl 3-formylazetidine-1-carboxylate from 1-Boc-3-hydroxymethylazetidine was as follows: to a stirred solution of oxalyl chloride (4.28 mL, 49.8 mmol) in dichloromethane (DCM, 5 mL) was added slowly and dropwise to dimethylsulfoxide (DMSO, 0.71 mL, 9.96 mmol) at -78 °C. The reaction mixture was continued to be stirred at this temperature for 15 minutes. Subsequently, tert-butyl 3-(hydroxymethyl)azetidine-1-carboxylate (0.69 g, 3.69 mmol) was added and triethylamine (2.1 mL, 14.75 mmol) was added immediately. The reaction system was gradually warmed to room temperature and diluted with DCM (30 mL). The reaction solution was washed with water and the organic phase was dried over anhydrous sodium sulfate (Na2SO4), filtered and concentrated under reduced pressure. The crude product was purified by column chromatography (using an Isolute column, eluent: heptane/ethyl acetate gradient, 0-100%) to give tert-butyl 3-formylazetidine-1-carboxylate (0.19 g, 27% yield).
