Resorcinol → 7-hydroxy-2,2-dimethyl-3,4-dihydro-2H-1-benzopyran-4-one

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Reaction Steps

Resorcinol (165 g) and 3,3-dimethylacrylic acid (100 g) were mixed, cooled in an ice bath, and treated carefully with concentrated sulfuric acid (180 mL). The internal temperature rose to 68° C. The mixture turned gradually to a viscous orange mass and the internal temperature dropped to 25° C. The ice bath was removed and stirring was continued overnight at room temperature (“RT”) during which the mixture solidified. Small amounts of water and ethyl acetate were carefully added alternatively until the mixture dissolved, and it was transferred to a 5 L conical flask with water (2 L) and ethyl acetate (1.5 L). The organic layer was separated and the aqueous layer was extracted with ethyl acetate. The combined organic layers were washed once with water and carefully treated with solid sodium bicarbonate until effervescence stopped. The organic layer was washed with water, concentrated in vacuo, and the resulting white solid was dissolved in 10% sodium hydroxide. The resulting solution was adjusted to pH 2 with concentrated hydrochloric acid and the resulting solid was filtered, dissolved in boiling glacial acetic acid (220 mL), stirred, diluted with boiling water (220 mL), and immediately cooled. The resulting solid was filtered, washed, and dried in vacuo at 50° C. to give the title compound (120 g).

Provenance & Evidence