[Cl:1][C:2]1[CH:3]=[CH:4][C:5]2[O:9][C:8]([CH3:10])=[N:7][C:6]=2[CH:11]=1.[N+:12]([O-])([OH:14])=[O:13].O1C2C=CC=CC=2N=C1>S(=O)(=O)(O)O>[Cl:1][C:2]1[C:3]([N+:12]([O-:14])=[O:13])=[CH:4][C:5]2[O:9][C:8]([CH3:10])=[N:7][C:6]=2[CH:11]=1Concentrated sulfuric acid (150 mL) was stirred mechanically and cooled in an ice/water bath. To this was gradually added 5-chloro-2-methylbenzoxazole (1), (75 g, 0.45 Moles), at such a rate that the temperature stayed at 30° C., over a 15–20 minute period. A solution of concentrated sulfuric acid (40 mL), and concentrated nitric acid (32 mL), was prepared and added drop by drop to the benzoxazole solution at such a rate that the temperature was maintained at approximately 20° C. When this acid solution had been added the cooling bath was removed and the mixture allowed to stir at room temperature for 1 hour. At the end of this period the solution was carefully poured onto ice with good stirring. Sufficient water was then added to get good mixing. The solid was filtered off, washed well with water followed by methanol and finally air dried. Yield 90.6 g.
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