General procedure for the synthesis of N-Boc-4-piperidine ethanol from tert-butyl 4-(2-ethoxy-2-oxo-substituted)piperidine-1-carboxylate: first, the above product (639 mg, 2.4 mmol) was dissolved in 6 mL of methanol, protected by argon, replaced three times with hydrogen and reacted overnight in a hydrogenation unit (4 atm H2). Upon completion of the reaction, the reaction solution was filtered through diatomaceous earth and washed with ethyl acetate. The filtrate was concentrated and purified by column chromatography to give a white solid product (722 mg, 100% yield). Subsequently, the above product (506 mg, 1.9 mmol) was dissolved in 10 mL of ether, cooled to -20 °C, and hydrogenated diisobutylaluminum (1.0 M, 5 mL, 5 mmol) was slowly added, and the reaction was carried out for 10 min until the raw material completely disappeared. The reaction mixture was poured into saturated potassium sodium tartrate solution and stirred at room temperature for 3 hours until clarified. The aqueous phase was extracted three times with ether, the organic phases were combined, washed with saturated NaCl solution and dried over anhydrous Na2SO4. After concentration, the product was purified by column chromatography to give a white solid product (368 mg, 86% yield).
