Ethyl cyanoacetate (40 g, 404 mmol) was dissolved in dichloromethane (200 mL) and cooled to 0°C under nitrogen protection. An ethanol solution of 45 wt.% hydrochloric acid (27.3 mL, 404 mmol) was added slowly and dropwise over 15 min with stirring. The reaction mixture was stirred continuously at 0 °C for 3 h, followed by standing overnight at -5 °C to -3 °C. The following day, dichloromethane (250 mL) was added to the reaction mixture and kept at 0 °C. A solution of triethylamine (113 mL, 807 mmol) in dichloromethane (50 mL) was added dropwise over 30 minutes. After the dropwise addition, the mixture was continued to be stirred at 0°C for 30 minutes. Subsequently, water (100 mL) was added and stirred for 5 minutes. The organic layer was separated, dried over anhydrous sodium sulfate and concentrated under reduced pressure. Diethyl ether (50 mL) was added to the residue and the solid was removed by filtration. The filtrate was dried to give ethyl 2-ethoxy-2-iminoacetate as a light yellow liquid (31.0 g, 214 mmol, 52.9% yield). NMR hydrogen spectrum (400 MHz, CDCl3) δ 8.78 (s, 1H), 4.36-4.28 (m, 4H), 1.40-1.35 (m, 6H).
