Hydrochloric Acid → 5-Formyl-2-hydroxyphenyl acetate

To a solution of 3,4-dihydroxybenzaldehyde (5.0 g) in N,N-dimethylformamide (36 mL) was added 60% sodium hydride (1.45 g) under ice-cooling, followed by stirring the reaction mixture at room temperature for 10 minutes. Then, after addition of acetic anhydride (3.6 mL), the reaction mixture was stirred at room temperature for 1 hour. To the reaction mixture was added 2N aqueous hydrochloric acid solution under ice-cooling, followed by extraction with ethyl acetate. The organic layer was washed with saturated aqueous sodium bicarbonate solution and saturated brine, dried and concentrated. The residue was purified by column chromatography on silica gel (ethyl acetate:hexane (volume ratio)=1:2 to 1:1) to give acetic acid 5-formyl-2-hydroxyphenyl ester (4.9 g).