Synthesis
A dichloromethane solution of benzyl chloroformate (17 g, 100 mmol) was added slowly and dropwise to a stirred dichloromethane (100 ml) solution of ethyl 2-piperidinecarboxylate (15 g, 95 mmol), triethylamine (27 ml, 191 mmol), and 4-dimethylaminopyridine (0.58 g, 4.8 mmol) at 0 °C. The reaction mixture was slowly warmed up to room temperature and stirred continuously at room temperature for 16 hours (overnight) followed by standing for 2 days. After completion of the reaction, the crude product was extracted with dichloromethane and washed sequentially with 1N hydrochloric acid, saturated aqueous sodium bicarbonate solution and brine. The organic phase was dried over anhydrous magnesium sulfate, filtered and concentrated in vacuum. The residue was purified by column chromatography on silica gel 60 (300 g) with cyclohexane/ethyl acetate as eluent to afford the light yellow oily target product ethyl N-Cbz-piperidine-2-carboxylate. Yield: 17.9 g (62% yield). The product was analyzed by HPLC (Method 6): retention time Rt = 4.91 min, maximum absorption wavelength λmax = 202 nm; mass spectrometry (ESI positive ion mode): m/z = 309 ([M+NH4]+).
References
[1] Patent: WO2005/82864, 2005, A1. Location in patent: Page/Page column 41-42
[2] Journal of the American Chemical Society, 2011, vol. 133, # 49, p. 19698 - 19701
[3] Angewandte Chemie - International Edition, 2012, vol. 51, # 42, p. 10660 - 10663
[4] Angew. Chem., 2012, vol. 124, # 42, p. 10815 - 10819,5
