Imidazole → (S)-tert-butyl 2-(2-cyanopyrrolidin-1-yl)-2-oxoethylcarbamate

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Reaction Conditions

Reaction Steps

In a dry three-neck flask under a nitrogen atmosphere, 286 mL of pyridine, [2-(2-carbamoyl-pyrrolidin-1-yl)-2-oxo-ethyl]-carbamic acid tert-butyl ester 1b (13.5 g, 49.8 mmol) and imidazole (7.11 g, 104.6 mmol) were added successively. The reaction system was cooled down to −35° C., and phosphorus oxychloride (19 mL, 204.2 mmol) was then added dropwise to the solution with stirring. After stirring for 1 hour at −35° C., the reaction mixture was allowed to increase to room temperature, and stirred for another 0.5 hour. Pyridine was evaporated under low temperature, and the reaction mixture was diluted with water, then extracted with ethyl acetate (200 mL×3). The combined organic extracts were washed with 50 mL of saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by silica gel column chromatography to obtain the title compound [2-(2-cyano-pyrrolidin-1-yl)-2-oxo-ethyl]-carbamic acid tert-butyl ester 1e (10.7 g, yield 84.9%) as a white powder.

Provenance & Evidence