Potassium Carbonate → 2-(4-fluorophenyl)-5,7-dihydroxy-3-methoxy-4H-benzopyran-4-one

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Reaction Steps

Under nitrogen atmosphere, 2-methoxy-1-(2,4,6-trihydroxyphenyl)ethanone (60 mg, 303.03 mmol), anhydrous potassium carbonate powder (250.9 g, 1.82 mmol), TBAB (tetrabutyl ammonium bromide, 145.9 mg, 454.52 mmol) and 4-fluorobenzoyl chloride (95.8 mg, 606 mmol) were dissolved in toluene (1200 mL), and refluxed for 6 hours. After cooling, toluene was removed, and then water (500 mL) was added. The aqueous solution was extracted with dichloromethane. The combined organic phase was washed with water and saturated brine, and dried over anhydrous sodium sulfate. A brown residue was obtained after removal of solvent. The residue was dissolved in a 5% potassium carbonate aqueous solution and heated to reflux for 2 hr. After cooling to ambient temperature, the mixture was acidified to pH 6 with 1N HCl solution, and extracted with dichloromethane three times. The combined organic phase was dried over anhydrous sodium sulfate, and the solvent was removed. The crude product was purified by silica gel column chromatography (eluent:ethyl acetate/petroleum ether, 1:5) and recrystallized in ethanol to give the desired compound (75 g, yield 81.9%).

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