6-Iodo-1-methyl-1H-benzo[d][1,3]oxazine-2,4-dione. To a stirred solution of 5-iodo-2-(methylamino)benzoic acid (10 g, 36 mmol), sodium carbonate (4 g, 36 mmol) and water (130 mL, 7218 mmol), cooled to 0° C., was slowly added, via addition funnel, a 2M phosgene (18 mL, 36 mmol) solution in toluene. After 2 hours, the precipitated product was isolated by filtration. The solids were washed with 100 mL of water, 150 mL of a 1:1 mixture of EtOH and ether, 100 mL of ether, and dried under vacuum to give the title compound.
