N-benzyl-3-phenylpiperidine (3-1, 65 g, 258.96 mmol) was added palladium carbon (12 g, 18%), anhydrous ethanol (300 mL) and glacial acetic acid (11 mL) in a reaction flask. The reaction was heated to 60 °C for 12 h under 1 atm hydrogen atmosphere. The reaction progress was monitored by TLC and stopped after confirming the complete reaction of the ingredients. The reaction mixture was filtered to remove palladium carbon and the filtrate was concentrated to dryness by rotary evaporation. The residue was dissolved in water (250 mL) and extracted with ethyl acetate (250 mL x 3), the organic layers were combined and dried over anhydrous sodium sulfate. After filtration, the solvent was removed by rotary evaporation to afford 35.2 g of 3-phenylpiperidine (1) in 89.3% yield, and the product was used directly in the subsequent reaction.
