Acetonitrile (220 mL) and DMF (3.82 mL, 49.4 mmol) were added to a 500 mL round bottom flask equipped with a stir bar. Cooled the mixture down to -5 °C and added oxalyl chloride (24.7 mL, 49.4 mmol, 2 M dichloromethane). The resulting mixture was stirred for 15 min, followed by the addition of a solution of 2-carbamoyl-piperidine-1- carboxylic acid tert-butyl ester (9.4 g, 41.2 mmol) in acetonitrile (50 mL) and pyridine (8.3 mL, 103 mmol). The reaction mixture was left stirring at room temperature overnight. The reaction mixture was concentrated in vacuo and the residue was dissolved in ethyl acetate (300 mL). The organic phase was successively washed with water (300 mL) and brine (200 mL), dried (sodium sulfate), filtered, and concentrated in vacuo to isolate tert-Butyl 2-cyanopiperidine-1-carboxylate (8.44 g, 97percent) as a yellow solid.
