(1) Preparation of 3-amino-7-hydroxy-2H-1-benzopyran-2-one. A mixture of N-(7-hydroxy-2-oxo-2H-1-benzopyran-3-yl) benzamide (230 mg, 0.82 mmol), 1-propanol (6 mL) and concentrated hydrochloric acid (2 mL) was heated and refluxed for 3 hours. Subsequently, concentrated hydrochloric acid (2 mL) was added additionally and refluxing was continued for 7 hours. After completion of the reaction, it was cooled to room temperature and the reaction mixture was slowly poured into saturated aqueous sodium bicarbonate solution and extracted with ethyl acetate. The organic phases were combined, washed sequentially with distilled water and saturated sodium chloride solution, dried over anhydrous sodium sulfate, and concentrated under reduced pressure to remove the solvent. The resulting crude product was purified by silica gel column chromatography (eluent ratio: dichloromethane/ethyl acetate = 2:1) to afford the target compound 3-amino-7-hydroxy-2H-benzopyran-2-one as a yellow solid (127 mg, 87.7% yield).1H-NMR (DMSO-d6, δ): 5.23 (2H, s), 6.65-6.70 (3H, m) ), 7.23 (1H, d, J = 8.4 Hz), 9.81 (1H, s).
