2,3-Dihydroxybenzoic Acid → 8-hydroxy-2,2-dimethyl-4H-benzo[d][1,3]dioxin-4-one

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Reaction Steps

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.

Provenance & Evidence