Phosgene → 6,7-Dimethoxy-2H-3,1-benzoxazine-2,4(1H)-dione

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Reaction Steps

To a mixture of 10.0 g (51.0 mmol) of 4,5-dimethoxyanthranilic acid in 80 mL of 1,4-dioxane was slowly added 100 mL (193 mmol) of a 1.93 molar solution of phosgene in toluene, at room temperature. The mixture was stirred overnight. The mixture was concentrated to yield a residue which was triturated with ethyl acetate-hexane (1:4), filtered, washed with hexane and dried to afford 11.0 g (97.2%) of the 4,5-dimethoxyisatoic anhydride as a gray solid. MS (Cl mode) m/z 206 (M-18, 100%), 224 (M+H, 51%).

Provenance & Evidence