Add 2-(2-nitroethoxy)tetrahydropyran (41 mL, 270 mmol) dropwise in toluene (100 mL) to a solution of (2-chloro-phenyl)-propynoic acid ethyl ester (28.3 g, 135 mmol), 1,4-phenylene diisocyanate (67 g, 420 mmol) and triethylamine (15 mL) in toluene (900 mL). Stir at reflux for 10 h. While still warm (˜70° C.), filter the reaction mixture through Celite®, washing the solids with EtOAc. Wash the filtrate with 1N HCl (500 mL) and brine (500 mL). Dry the organics over Na2SO4, filter and concentrate under reduced pressure. Purification by flash chromatography (silica gel, 85:15 Hexanes/EtOAc) gives the title compound (46.5 g, 94%). MS (m/e): 282 (M−C5H8O+H+); 1H NMR (300 MHz, CDCl3) δ 7.35–7.55 (m, 4H), 5.09 (d, J=13 Hz, 1), 4.85–4.91 (m, 2H), 4.15–4.22 (m, 2H), 3.91–4.01 (m, 1H), 3.52–3.61 (m, 1H), 1.49–1.92 (m, 6H), 1.12 (t, J=7 Hz, 3H); TLC Rf=0.53 (7:3 Hexanes/EtOAc).
