Triphenylphosphine (786 mg) was added to a solution of N-tert-butoxycarbonyl-4-hydroxypiperidine (603 mg), 2-chloro-5-methylphenol (428 mg) and diethyl azodicarboxylate (522 mg) in tetrahydrofuran (10 mL) at room temperature. After stirring at room temperature for 18 hr, the reaction mixture was evaporated in vacuo. The residue was purified by silica gel column chromatography (ethyl acetate:hexane=1:6, v/v) to give the titled compound (489 mg) as a colorless oil: 1H NMR (400 MHz, CDCl3) δ 1.46 (s, 9H), 1.84 (m, 4H), 2.28 (s, 3H), 3.44 (m, 2H), 3.65 (ddd, J=4.0, 8.0, 12.7 Hz, 2H), 4.49 (m, 1H), 6.69 (d, J=8.0 Hz, 1H), 6.75 (s, 1H), and 7.19 (d, J=8.0 Hz, 1H).
