To a solution of 1-t-butoxycarbonyl-4-hydroxypiperidine (3.32 g), 2-chloro-4-nitrophenol (2.36 g) and triphenylphosphine (5.11 g) in dichloromethane (60 ml), diethyl azodicarboxylate (3.10 ml) was added dropwise with stirring under ice-cooling, and the resulting mixture was stirred at room temperature for 18 hours and then evaporated in vacuo. The residue obtained was purified by chromatography on a silica gel column using a mixed solvent of hexane and ethyl acetate (5:2) as the eluent to afford the title compound (3.90 g, yield: 76%) as a pale yellow solid.
