[F:1][C:2]1[CH:12]=[CH:11][C:5]2[NH:6][C:7](=[O:10])[CH2:8][O:9][C:4]=2[CH:3]=1.[I:13]Cl.S(=O)(O)[O-].[Na+]>C(O)(=O)C>[I:13][C:12]1[C:2]([F:1])=[CH:3][C:4]2[O:9][CH2:8][C:7](=[O:10])[NH:6][C:5]=2[CH:11]=17-Fluoro-2H-1,4-benzoxazin-3(4H)-one (15.8 g) was mixed with iodine monochloride (15.6 g) in acetic acid (150 ml) and heated to reflux for 36 h. The cooled mixture was treated with saturated aqueous sodium bisulfite until the color was dissipated. The solid was filtered and washed well with water. The solid was air dried and dried further by dissolution in dimethylformamide (100 ml) and evaporated to dryness under reduced pressure to give the desired product (26.3 g) contaminated with some starting material. (The reaction can be taken to completion by addition of more iodine monochloride and refluxing for 24 h longer.) The crude product was used in Step B.
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