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

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).

1. temperaturecooled in an ice bath
2. customrose to 68° C
3. additionthe internal temperature dropped to 25° C
4. customThe ice bath was removed
5. custom(“RT”)
6. additionSmall amounts of water and ethyl acetate were carefully added alternatively until the mixture
7. dissolutiondissolved
8. customit was transferred to a 5 L conical flask with water (2 L) and ethyl acetate (1.5 L)
9. customThe organic layer was separated
10. extractionthe aqueous layer was extracted with ethyl acetate
11. washThe combined organic layers were washed once with water
12. additioncarefully treated with solid sodium bicarbonate until effervescence
13. washThe organic layer was washed with water
14. concentrationconcentrated in vacuo
15. dissolutionthe resulting white solid was dissolved in 10% sodium hydroxide
16. filtrationthe resulting solid was filtered
17. dissolutiondissolved
18. stirringstirred
19. additiondiluted with boiling water (220 mL)
20. temperatureimmediately cooled
21. filtrationThe resulting solid was filtered
22. washwashed
23. customdried in vacuo at 50° C.

ORD record

ord-0aa6419e1e424de4acb56e37fbc0af91

Source dataset

uspto-grants-2003_01

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06506790B1