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) was added dropwise diethyl azodicarboxylate (1.4 ml) in an ice bath and the mixture was stirred at room temperature for 24 hours. The reaction mixture was concentrated in vacuo. The residue was purified by chromatography on a silica gel column using dichloromethane as an eluant to give the desired compound (2.28 g, yield 88%) as a pale yellow oil.
