Phthalic Anhydride → 2-(2,4-Dihydroxy-3-methylbenzoyl)benzoic acid

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Reaction Steps

Aluminum chloride (21.4 g, 161 mmol) was added to a stirring suspension of phthalic anhydride (6 g, 40 mmol) in tetrachloroethane (200 mL) under nitrogen. 1,3-Dihydroxy-2-methylbenzene (5 g, 40 mmol) was added and the mixture quickly thickened. After the precipitates were broken up with a spatula the reaction continued for 1 hour. The solution was diluted with ethyl acetate (˜600 mL) and washed with 1M hydrochloric acid (2×200 mL). The product was extracted from the organic layer into a saturated solution of sodium bicarbonate in water (600 mL). The basic aqueous phase was acidified with 3M hydrochloric acid to a pH of 5. The product was extracted from the aqueous phase into ethyl acetate (400 mL), washed with brine (2×100 mL), dried over magnesium sulfate and concentrated to give a brownish solid. The solid was slurried in dichloromethane (20 mL) and filtered to give 2-(2,4-dihydroxy-3-methylbenzoyl)benzoic acid as an off white powder (4.6 g, 16.9 mmol, 42% yield).

Provenance & Evidence