(2E)-3-(ethoxy)-N-(4-iodophenyl)-2-acrylamide (33 g, 104 mmol) was added batchwise to stirred concentrated sulfuric acid (300 mL) at 0 °C. The reaction mixture was stirred continuously for 2 hours at room temperature. Subsequently, the reaction mixture was quenched by slowly pouring it into about 1 kg of ice. The resulting solid product was collected by filtration and washed sequentially with water (3 times) and acetonitrile (2 times). Finally, the solid was dried under vacuum to afford 6-iodo-2-hydroxyquinoline as an off-white solid (27.1 g, yield: 96%). The structure of the product was confirmed by 1H NMR (400 MHz, chloroform-d) and ES-LCMS: 1H NMR δ= 6.73 (d, J = 9.6Hz, 1H), 7.17 (d, J = 8.8Hz, 1H), 7.74 (d, J = 9.6Hz, 1H), 7.77 (dd, J = 8.8,1.4Hz, 1H), 7.93 ( d, J = 1.4 Hz, 1H); ES-LCMS: m/z 272 (M + 1).
