Acetic Acid → 5-Ethyl-2H-3,1-benzoxazine-2,4(1H)-dione

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Reaction Steps

5-Ethylisatin (70 g), acetic acid (200 ml) and concentrated sulfuric acid (0.8 ml) were charged in a 500 ml two-necked flask, followed by stirring at room temperature. Then, 50 ml of aqueous 30% hydrogen peroxide was added dropwise and, after stirring at 60° to 65° C. for additional one hour, the mixture was cooled. The deposited solid was filtered, washed with water and dried under vacuum to obtain 6-ethylisatoic anhydride. Crude yield: 35 g

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