3-Methyl-4-nitrophenol (1.74 g, 11.4 mmol), triphenylphosphine (5.98 g, 22.8 mmol), and phenylmethyl 4-hydroxy-1-piperidinecarboxylate (3.99 g, 17.0 mmol) were dissolved in DCM with stirring and cooled to 0° C. Diisopropyl azodicarboxylate (3.35 mL, 17.0 mmol) was added via syringe. The reaction was stirred for 10 min and allowed to warm to rt. The reaction was stirred overnight and adsorbed onto silica gel. The crude material was purified by flash chromatography, and fractions containing product were concentrated in vacuo. The material was contaminated with 3-methyl-4-nitrophenol. The material was dissolved in diethyl ether and washed with 2N NaOH solution (3×), H2O, and brine. The organic layer was dried over MgSO4, filtered, and concentrated in vacuo to provide 3.67 g (87%) of the title compound. 1H NMR (400 MHz, DMSO-d6) δ 8.02 (d, J=9.0 Hz, 1H), 7.42-7.24 (m, 5H), 7.06 (d, J=2.4 Hz, 1H), 7.01 (dd, J=9.1, 2.7 Hz, 1H), 5.07 (s, 2H), 4.76 (ddd, J=7.7, 4.2, 4.0 Hz, 1H), 3.81-3.64 (m, 2H), 3.31 (br. s., 2H), 2.52 (s, 3H), 2.01-1.88 (m, 2H), 1.63-1.49 (m, 2H).
