To a solution of 4-fluoro-5-((2-fluoro-4-iodophenyl)amino)benzo[d]oxazole-6-carboxylic acid (500 mg, 1.2 mmol) in CH2Cl2 was added HOBt (254 mg, 1.63 mmol) and EDCI (314 mg, 1.63 mmol). The mixture was stirred for 1 h and O-(2-(vinyloxy)ethyl)hydroxylamine (172 mg, 1.62 mmol) was added. After stirring for 4 h at ambient temperature, the reaction was treated with saturated NH4Cl (aq., 20 mL). The resultant mixture was extracted with CH2Cl2 (30 mL×3). The combined organic extracts were washed with water (30 mL×2) and brine (30 mL) sequentially, dried over Na2SO4, filtered and concentrated in vacuo. The crude product was purified by column chromatography on silica gel (CH2Cl2/MeOH, 20:1, v/v) and gave the desired product (white solid, 598 mg, 98% yield). 1H NMR (400 MHz, DMSO-d6): δ 11.82 (s, 1H), 8.96 (s, 1H), 8.01 (s, 1H), 7.88 (s, 1H), 7.53 (d, J=10.8 Hz, 1H), 7.28 (d, J=8.1 Hz, 1H), 6.50 (dd, J=13.9, 6.6 Hz, 1H), 6.40 (d, J=6.0 Hz, 1H), 4.18 (d, J=14.5 Hz, 1H), 3.99 (m, 3H), 3.83 (s, 2H).
