398489-26-4

50586-62-4

1153949-11-1

Under nitrogen protection, 24.8 g of cyanomethyl diethyl phosphate and 300 mL of anhydrous tetrahydrofuran were added to a 1000 mL four-necked flask. The reaction mixture was cooled to -15 to -10 °C under nitrogen protection and 128.5 mL of 1.0 M potassium tert-butanolate in tetrahydrofuran solution was slowly added while controlling the temperature below -5 °C. After addition, the reaction continued to be stirred at -10 to -5 °C for 3 hours. Subsequently, keeping the temperature below -5 °C, a tetrahydrofuran solution of 1-Boc-3-azetidinone was added slowly and dropwise (20.0 g 1-Boc-3-azetidinone dissolved in 67 mL of tetrahydrofuran). After dropwise addition, the reaction temperature was maintained at -10 to -5°C with continued stirring for 2 hours. Next, the reaction mixture was slowly warmed to 25 to 30 °C and stirred at this temperature for 16 hours. Upon completion of the reaction, the layers were separated by slowly adding 300 mL of 12.5% aqueous sodium chloride solution. The aqueous phase was extracted with 300 mL of ethyl acetate. The organic phases were combined and washed with 200 mL of brine. A final 20.65 g white solid product tert-butyl 3-(cyanomethylene)azetidine-1-carboxylate was obtained in 91% yield.