Synthesis
Step 1: Synthesis of 1-benzyl 3-ethylpiperidine-1,3-dicarboxylate
Benzyl chloroformate (191 mL, 1.34 mol) was slowly added dropwise to a cooled solution of ethyl piperidine-3-carboxylate (200 g, 1.27 mol) and triethylamine (266 mL, 1.91 mol) in dichloromethane (1000 mL) at 0 °C. The reaction mixture was gradually warmed to room temperature and stirred for 3 hours. Upon completion of the reaction, the reaction was quenched by the addition of 1N HCl aqueous solution. The reaction mixture was extracted several times with dichloromethane and the organic phases were combined. The organic phase was washed sequentially with water, saturated aqueous NaHCO3 solution, water and brine, and then dried with anhydrous MgSO4. After filtration, the filtrate was concentrated under reduced pressure to afford the target product 1-benzyl 3-ethylpiperidine-1,3-dicarboxylate as an oil (359.8 g, 97% yield).LC/MS analysis showed m/z 292.2 ([M+H]+).
References
[1] Tetrahedron Letters, 2011, vol. 52, # 26, p. 3266 - 3270
[2] Patent: US2008/318991, 2008, A1. Location in patent: Page/Page column 7-8
[3] Patent: WO2009/140320, 2009, A1. Location in patent: Page/Page column 72
[4] Patent: WO2013/12829, 2013, A1. Location in patent: Paragraph 00273
[5] Patent: US8080566, 2011, B1. Location in patent: Page/Page column 44
