C(Cl)(Cl)=O.[NH2:5][C:6]1[C:14]([CH3:15])=[CH:13][C:12]([CH3:16])=[CH:11][C:7]=1[C:8](O)=[O:9].CC1C=C(C)C2[NH:26]C(=O)OC(=O)C=2C=1.C12C(=CC=CC=1)NC(=O)OC2=O.[NH4+].[OH-]>O1CCOCC1>[NH2:5][C:6]1[C:14]([CH3:15])=[CH:13][C:12]([CH3:16])=[CH:11][C:7]=1[C:8]([NH2:26])=[O:9]Liquid phosgene (55 g.) is added to a stirred solution of 30.1 g. (0.182 mol.) of 2-amino-3,5-dimethylbenzoic acid in 300 ml. of dioxane. The temperature is raised to 40°-45° C. and held for 2 hr. The mixture is stirred overnight at room temperature and filtered. The filter cake is washed with diethyl ether, giving 33 g. (95%) of 6,8-dimethyl-2H-3, 1-benzoxazine-2,4(1H)-dione; m.p.>300° C. The isatoic anhydride is then added to 435 ml. of 1 M. NH4OH. The mixture is stirred overnight at room temperature, brought to reflux for 2 hr. cooled, filtered, and crystallized (EtOH), giving 13.4 g. (47%) of product, m.p. 162°-167° C.
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