Piperidine-4-carboxamide (5 g, 39 mmol) and benzyl chloroformate (5.54 mL, 39 mmol) were added dropwise to 1N NaOH solution (39 mL, 39 mmol) in a solvent mixture of water (30 mL) and acetone (40 mL), and the pH was maintained between 6 and 8 during the reaction. The reaction mixture was stirred at room temperature for 3 hours. Subsequently, the acetone was removed by evaporation, the resulting precipitate was collected by filtration and dried under reduced pressure at 70 °C to afford benzyl-4-carbamoylpiperidine-1-carboxylate 7.75 g in 76% yield. The product was analyzed by HPLC with a retention time (Rt) of 4.54 min. 1H NMR (600 MHz, DMSO-d6) δ ppm: 7.41-7.29 (m, 5H), 7.25 (br.s, 1H), 6.76 (br.s, 1H), 5.07 (s, 2H), 4.06-3.81 (m, J=13.2 Hz, 2H ), 2.92-2.72 (m, 2H), 2.27 (tt, J=3.7,11.5Hz, 1H), 1.75-1.64 (m, 2H), 1.40 (dq, J=4.3,12.4Hz, 2H). The high resolution mass spectrometry (HRMS) (ESI) [M+H]+ calculated value of C14H18O3N2 was 263.1390 and the measured value was 263.1390.
