The general procedure for the synthesis of 3,4,5-trihydroxybenzaldehyde from butyraldehyde was as follows: 2.0 g of butyraldehyde was accurately weighed into a 250 ml two-necked flask, and about 100 ml of 1,2-dichloroethane was added as a solvent, and stirred thoroughly until dissolved. After cooling the reaction system to 0°C, 7.3 g of anhydrous aluminum trichloride was slowly added and the reaction was stirred for 30 minutes at this temperature. Subsequently, 8.7 g of pyridine was added dropwise through a constant pressure dropping funnel over a period of 20 min, and the reaction mixture was heated to 90 °C and refluxed for 4 h after completion of the dropwise addition. Upon completion of the reaction, the system was cooled to 0 °C and neutralized to pH neutral with a 3 mol/L hydrochloric acid solution. Extraction was carried out with about 250 mL of ethyl acetate and the extract was washed 5 times with ice water to remove impurities. The organic layers were combined, dried by adding anhydrous sodium sulfate, filtered and distilled under reduced pressure to remove the solvent to give a brown solid crude product. The crude product was purified by 200-300 mesh silica gel column chromatography to give 0.83 g of 3,4,5-trihydroxybenzaldehyde in 49% yield. For further purification, the resulting product was recrystallized from water to give an acicular light white solid.
