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 (10 mL) 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.). The resultant mixture was extracted with CH2Cl2 (30 mL×3). The combined organic extracts were washed with water (30 mL) and brine (30 mL), dried over Na2SO4, filtered and concentrated in vacuo. The crude product was purified by column chromatography on silica gel (CH2Cl2/MeOH, 100:1, v/v) and gave the desired product (white solid, 450 mg, 74.8% 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).
