反应详情

Trifluoroacetic acid anhydride (42.0 mL, 300 mmol) was added dropwise to a cooled (−5° C.) solution of 2,3-dihydroxybenzoic acid (8.30 g, 53.9 mmol) in trifluoroacetic acid (83 mL), with stirring. Acetone (14.0 mL, 190 mmol) was then added dropwise over 27 minutes, and the mixture stirred and allowed to warm gradually to room temperature over 16.5 hours. The volatiles were concentrated under vacuum, the residue was dissolved in ethyl acetate (100 mL), and the solution slowly added to a rapidly stirred saturated aqueous sodium bicarbonate solution (200 mL). After gas evolution ceased, the mixture was extracted with ethyl acetate (3×100 mL). The combined organic extracts were dried over magnesium sulfate, filtered, concentrated, and purified by silica gel chromatography (ethyl acetate/heptane) to give 8-hydroxy-2,2-dimethyl-4H-1,3-benzodioxin-4-one (123a, 3.55 g, 34% yield) as an off-white solid.

1. stirringthe mixture stirred
2. concentrationThe volatiles were concentrated under vacuum
3. dissolutionthe residue was dissolved in ethyl acetate (100 mL)
4. additionthe solution slowly added to a rapidly stirred saturated aqueous sodium bicarbonate solution (200 mL)
5. extractionthe mixture was extracted with ethyl acetate (3×100 mL)
6. dry with materialThe combined organic extracts were dried over magnesium sulfate
7. filtrationfiltered
8. concentrationconcentrated
9. custompurified by silica gel chromatography (ethyl acetate/heptane)