To a solution of 1-t-butoxycarbonyl-4-hydroxypiperidine (1.45 g), 2-trifluoromethyl-4-nitrophenol (1.38 g), which was prepared from 3-trifluoromethylnitrobenzene according to the method described in J. Org. Chem., 63, 4199 (1998), and triphenylphosphine (2.27 g) in dichloromethane (65 ml), diethyl azodicarboxylate (1.4 ml) was added dropwise with stirring under ice-cooling, and the resulting mixture was stirred at room temperature overnight and then evaporated in vacuo. The residue obtained was purified by chromatography on a silica gel column using dichloromethane as the eluent to afford the title compound (2.28 g, yield: 88%) as a pale yellow oil.
