8-Hydroxy-quinoline-5-carbaldehyde

148-24-3

67-66-3

2598-30-3

8-Hydroxyquinoline (5 g, 0.034 mol) was dissolved in ethanol (50 mL), followed by the addition of sodium hydroxide (10 g, 0.25 mol) dissolved in water (15 mL). The mixed solution was heated to reflux and trichloromethane was added slowly and dropwise over 30 minutes. After continuing the reflux reaction for 20 h, ethanol and unreacted trichloromethane were removed by distillation under reduced pressure. The residue was dissolved in water (150 mL) and the pH was adjusted to slightly acidic with dilute hydrochloric acid. The resulting yellow solid was extracted with dichloromethane and the extract was purified by column chromatography (silica gel as stationary phase and dichloromethane/methanol as eluent) to give 8-hydroxyquinoline-5-carbaldehyde as a final white solid (115 mg, 0.67 mmol). The structure of the product was confirmed by 1H-NMR (CDCl3, 400 MHz) and 13C-NMR (DMSO-d6, 400 MHz): 1H-NMR δ = 10.16 (s, 1H), 9.71 (dd, 1H, J = 1.6Hz, 8.4Hz), 8.89 (dd, 1H, J = 1.6Hz, 4.0Hz), 8.02 (d , 1H, J = 8.0 Hz), 7.69 (q, 1H, J = 4.0 Hz), 7.30 (d, 1H, J = 8.0 Hz); 13C-NMR δ = 193.1, 160.5, 149.9, 141.1, 138.9, 133.9, 127.7, 125.5, 123.4, 111.7.