2-Benzylpiperidin-4-one (17 g) and di-tert-butyl carbonate (21.8 g) were mixed in dichloromethane (500 ml). The reaction mixture was stirred at room temperature for 48 hours. After completion of the reaction, the solvent was removed by rotary evaporation. The organic layer was separated by dissolving the residue in water and toluene. The aqueous layer was extracted again with toluene. All organic layers were combined, dried with anhydrous sodium sulfate, filtered and concentrated to give 38 g (100% yield) of (±)-1-tert-butoxycarbonyl-2-benzyl-4-piperidone (Intermediate 6).
