Potassium Carbonate → 2-(3-fluoro-4-methoxyphenyl)-5,7-dihydroxy-3-methoxy-6,8-di(3-methyl-2-buten-1-yl)-4H-benzopyran-4-one

Participants

Reaction Steps

Under nitrogen atmosphere, 2-methoxy-1-[2,4,6-trihydroxy-3,5-di(3-methyl-2-buten-1-yl)phenyl]ethanone (300 mg, 0.897 mmol), anhydrous potassium carbonate powder (744 mg, 5.38 mmol), TBAB (tetrabutyl ammonium bromide, 434 mg, 1.346 mmol), and 3-fluoro-4-methoxybenzoyl chloride (388 mg, 2.057 mmol) were dissolved in toluene (84 mL), and refluxed for 6 hours. After cooling, toluene was removed, and then water (20 mL) was added. The aqueous solution was extracted with ethyl acetate. 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 20 mL methanol-H2O (4:1) mixture, to which was added potassium hydroxide (1 g). The mixture was heated to reflux for 2 hours, then cooled to ambient temperature, acidified to pH 4 with 1N HCl solution, and extracted with dichloromethane three times. The combined organic phase was dried over anhydrous sodium sulfate, with removal of solvent. The crude product was purified by silica gel column chromatography (eluent: ethyl acetate/petroleum ether, 1:50) to give the desired compound (137.8 mg, yield 32.6%). 1H NMR (400 MHz, CDCl3): δ=12.89 (s, 1H), 7.94 (dt, 1H, J1=8.8 Hz, J2=2.0 Hz), 7.90 (dd, 1H, J1=8.8 Hz, J2=2.0 Hz), 7.08 (t, 1H, J=8.8 Hz), 6.36 (s, 1H), 5.27-5.23 (m, 2H), 3.99 (s, 3H,), 3.88 (s, 3H), 3.54 (d, 2H, J=6.8 Hz), 3.47 (d, 2H, J=6.8 Hz), 1.85 (s, 3H), 1.84 (s, 3H), 1.77 (s, 3H), 1.75 (s, 3H); LC-MS (ESI) m/z 469.5 [M+14]+.

Provenance & Evidence