54287-99-9

107-86-8

95-01-2

54287-99-9

The general procedure for the synthesis of 5-hydroxy-2,2-dimethyl-2H-chromene-6-carbaldehyde from 3-methyl-2-butenal and 2,4-dihydroxybenzaldehyde was as follows: 2,4-dihydroxybenzaldehyde (15) (3 g, 20.17 mmol), calcium hydroxide (1.543 g, 20.8 mmol), and 150 mL of methanol were added to a two-necked round-bottom flask. Subsequently, 3-methyl-2-butenal (9.135 g, 108.6 mmol) was added slowly and dropwise. The reaction mixture was stirred continuously at room temperature for 48 hours. After completion of the reaction, the pH of the reaction solution was adjusted to 1-2 with 1 M hydrochloric acid to quench the reaction. Methanol was removed by distillation under reduced pressure and the remaining aqueous phase was extracted with ethyl acetate (3 x 150 mL). The organic phases were combined, washed sequentially with brine (2 × 100 mL), dried over anhydrous sodium sulfate, filtered and the organic solvent was concentrated under reduced pressure. The crude product was purified by silica gel fast column chromatography (eluent: hexane/ethyl acetate, 9:1). The final product 5-hydroxy-2,2-dimethyl-2H-chromene-6-carboxaldehyde (16) was crystallized using a solvent mixture of hexane/ethyl acetate (3:1) to give a yellow solid (2.06 g, 50% yield).