General procedure for the preparation of 2-(2-methoxyethyl)piperidine hydrochloride: to a solution of 2-(2-methoxyethyl)pyridine (25 g, 182 mmol) in anhydrous ethanol (120 mL) was slowly added concentrated hydrochloric acid (5 mL) followed by platinum oxide (1.1 g, 4.8 mmol). The reaction mixture was placed in a Parr oscillator, pressurized to 50 psig under hydrogen atmosphere, and shaken for 15 hours. After completion of the reaction, the reaction solution was filtered through Celite TM and the filtrate was concentrated under reduced pressure. The concentrated residue was dissolved in water and extracted sequentially with dichloromethane and ethyl acetate. The organic phase extracts were combined and concentrated under reduced pressure to recover unreacted material. The aqueous phase was concentrated under reduced pressure to afford the target product 2-(2-methoxyethyl)piperidine hydrochloride as a white solid (3.14 g, 10% yield). The obtained product could be directly used in the subsequent reaction without further purification. The structure of the product was confirmed by 1H NMR (400 MHz, D2O): δ1.25-1.55 (m, 3H), 1.65-1.90 (m, 5H), 2.75-2.83 (m, 1H), 3.05-3.15 (m, 1H), 3.14-3.23 (m, 4H), 3.41-3.50 (m, 2H).
