[Synthesis]
The general procedure for the synthesis of 9-hydroxyanthracene from 9-anthracenecarboxaldehyde is as follows: in a 1,000 mL round-bottomed flask equipped with a stirrer and thermometer, 20.00 g of 9-formylanthracene and 200 mL of acetic acid were added. After stirring the reaction mixture for 15 minutes, 45.68 g of sodium percarbonate was slowly added at room temperature. Subsequently, the reaction temperature was raised to 30 °C and the reaction mixture was continuously stirred, and the progress of the reaction was monitored by thin-layer chromatography (TLC; unfolding agent: n-hexane/ethyl acetate, 4:1). Upon completion of the reaction, the acetic acid was removed by distillation under reduced pressure and the reaction mixture was concentrated. To the concentrate, 200 mL of toluene was added and the toluene layer was washed sequentially with 100 mL of water, 100 mL of 10% sodium thiosulfate solution and 100 mL of 10% sodium hydroxide solution. Next, 22.75 g of methanol and 0.65 g of sulfuric acid were added to the toluene layer, and the resulting methyl formate and methanol were removed by distillation at atmospheric pressure. Then, 82.47 g of 10% sodium hydroxide solution was added to the toluene layer, and after stirring at room temperature, the toluene layer and the basic aqueous solution layer were separated using a partition funnel. The basic aqueous solution layer was washed several times with 20 mL of dichloromethane to remove small amounts of residual impurities (e.g., anthracene, 9-formylanthracene, etc.) until the aqueous layer was free of impurities by TLC. Subsequently, the basic aqueous solution layer was adjusted to a slightly acidic pH with concentrated sulfuric acid. the slightly reddish powder obtained was filtered and recrystallized in toluene to obtain pure 9-hydroxyanthracene (yield: 78%, purity: 99.56%). |