[Cl:1][C:2]1[C:10]2[O:9][N:8]=[C:7]([C:11]3[CH:16]=[CH:15][CH:14]=[CH:13][C:12]=3[F:17])[C:6]=2[CH:5]=[CH:4][C:3]=1[O:18][CH2:19][C:20]([OH:22])=[O:21].[N+:23]([O-])([OH:25])=[O:24]>>[Cl:1][C:2]1[C:10]2[O:9][N:8]=[C:7]([C:11]3[CH:16]=[C:15]([N+:23]([O-:25])=[O:24])[CH:14]=[CH:13][C:12]=3[F:17])[C:6]=2[CH:5]=[CH:4][C:3]=1[O:18][CH2:19][C:20]([OH:22])=[O:21]To a solution of 10.0 g of {[7-chloro-3-(2-fluorophenyl)-1,2-benzisoxazol-6-yl]oxy}acetic acid in 70 ml of ice-cold sulfuric acid, 2.5 ml of 16N nitric acid is added. The reaction mixture is stirred for 2 hr in the cold and then allowed to warm to room temperature over 1 hr. The reaction mixture is then poured onto ice and the solid is collected. The filter cake is washed with water until the washes are no longer acidic and then recrystallized from acetic acid to afford {[7-Chloro-3-(2-fluoro-5-nitrophenyl)-1,2-benzisoxazol-6-yl]oxy}acetic acid, mp 238°-240° C.
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