83-30-7

67-64-1

137571-73-4

The general procedure for the synthesis of 5,7-dihydroxy-2,2-dimethyl-4H-1,3-benzodioxan-4-one from 2,4,6-trihydroxybenzoic acid (850 mg, 5 mmol) and acetone was as follows: 2,4,6-trihydroxybenzoic acid was dissolved in trifluoroacetic acid (10 mL) and the mixture was cooled in an ice water bath. Trifluoroacetic anhydride (4.8 mL, 38.5 mmol) was slowly added dropwise with stirring, keeping the reaction temperature between -10°C and 0°C. After the dropwise addition, stirring was continued at the same temperature for 5 minutes. Subsequently, anhydrous acetone (3.7 mL, 50 mmol) was added dropwise to the reaction mixture. After completion of dropwise addition, the reaction mixture was removed from the ice water bath and stirred at room temperature for 1 to 7 days. After completion of the reaction, the reaction mixture was diluted with ethyl acetate and the pH was adjusted to neutral with saturated aqueous sodium bicarbonate. The organic and aqueous layers were separated and the aqueous layer was extracted four times with ethyl acetate. All organic layers were combined and washed three times with saturated brine. The organic phase was dried over anhydrous sodium sulfate and purified by column chromatography (eluent ratio: hexane:ethyl acetate=20:1 to 10:1) to afford the white solid product 5,7-dihydroxy-2,2-dimethyl-4H-1,3-benzodioxan-4-one (401 mg, 75% yield).