General procedure for the synthesis of 1-phenylpiperidine-4-carbaldehyde from (1-phenyl-4-piperidinyl)methanol: (1-phenyl-4-piperidinyl)methanol (0.81 g, 4.23 mmol) and 1,8-diazabicyclohexadec-7-ene (DBU, 1.29 g, 8.46 mmol) were dissolved in anhydrous dichloromethane (17 mL) and the mixture was cooled to - 78 °C. A solution of N-tert-butylphenylsulfinimidyl chloride (1.0 g) in dichloromethane (5 mL) was slowly added with stirring, keeping the reaction temperature below -60 °C and stirring continuously for 1 hour. Upon completion of the reaction, water was added to the reaction mixture and extracted with ether. The organic layers were combined, dried with anhydrous magnesium sulfate (MgSO?), filtered and concentrated under reduced pressure. The resulting crude product was purified by silica gel column chromatography with the eluent of petroleum ether/ethyl acetate (4:1, v/v) to afford 1-phenylpiperidine-4-carbaldehyde (720 mg, 90% yield).1H NMR (400 MHz, CDCl?) δ ppm: 1.75-1.85 (m, 2H), 2.00-2.06 (m, 2H), 2.36-2.46 (m, 1H), 2.83-2.90 (m, 2H), 3.61 (t, J = 3.8 Hz, 1H), 3.64 (t, J = 3.8 Hz, 1H), 6.84-6.96 (m, 3H), 7.23-7.29 (m, 2H), 9.71 (s, 1H).
