Phosgene → 8-methyl-2,4-dihydro-1H-3,1-benzoxazine-2,4-dione

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Reaction Steps

To a mixture of 10.0 g (66.0 mmol) of 3-methylanthranilic acid in 60 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 in vacuo to yield a residue which was triturated with ethyl acetate-hexane (1:4), filtered, washed with hexane and dried to afford 11.66 g (99.5%) of the 3-methylisatoic anhydride as an off white solid. MS (Cl mode) m/z 160 (M-18, 100%), 178 (M+H, 90%).

Provenance & Evidence