To a stirred solution of (E)-2-(4-butoxy-3-methoxystyryl)-6-(4-hydroxy-3-methoxyphenyl)-4H-pyran-4-one 4b (1.30 mg, 3.08 mmol) in Ac2O (100 mL) at room temperature was added malononitrile (1.00 g, 15.14 mmol, 4.92 eq.) and the mixture was refluxed at 140°C during 3h (CCM, SiO2, DCM 100%). The reaction mixture was cooled to room temperature and then quenched with water (100 mL). Under stirring conditions, Na2CO3 (1M) was added to the mixture in batches and the pH value of the mixture was adjusted to 7. The crude product was extracted with DCM and the organic phase was separated. The aqueous phase was further extracted with DCM (4 x 50 mL). The combined organic phase was washed with water (3 x 50 mL) and brine (3 x 50 mL) then dried over Na2SO4, filtered, and evaporated under reduced pressure. Chromatography on silica gel with DCM 100% afforded the title compound 5b as a brown solid (1. 49