The general procedure for the synthesis of benzyl 3-piperidinecarboxylate from benzyl 1-Boc-piperidine-3-carboxylate was as follows: benzyl 1-(tert-butoxycarbonyl)piperidinecarboxylate (7.11 g, 22.3 mmol) was dissolved in dichloromethane (20 mL) and trifluoroacetic acid (43 mL, 558 mmol) was added slowly. The reaction mixture was stirred at room temperature for 3 hours. Upon completion of the reaction, the solvent was removed by concentration under reduced pressure and water was added to the residue, followed by dropwise addition of 1 mol/L aqueous sodium hydroxide to adjust the pH to basic. The aqueous phase was extracted with ethyl acetate and the organic layers were combined, washed with saturated brine and dried over anhydrous sodium sulfate. After filtration, the solvent was evaporated under reduced pressure to give benzyl 3-piperidinecarboxylate as a yellow oil (5.97 g, quantitative yield). The product was confirmed by 1H NMR (400 MHz, DMSO-d6): δ 1.45-1.70 (3H, m), 1.92-1.96 (1H, m), 2.59-2.69 (2H, m), 2.81 (1H, t, J = 9.8 Hz), 2.94-3.02 (1H, m), 3.21 (1H, dd, J = 12.6, 3.3 Hz), 5.10 (2H, d, J = 3.1 Hz), 7.27-7.38 (5H, m). Mass spectral analysis showed the molecular ion peak (EI+, m/z): 219 (M+).
