[Cl-].[Al+3].[Cl-].[Cl-].[C:5]1(=[O:15])[O:10][C:8](=[O:9])[C:7]2=[CH:11][CH:12]=[CH:13][CH:14]=[C:6]12.[OH:16][C:17]1[CH:22]=[CH:21][CH:20]=[C:19]([OH:23])[C:18]=1[CH3:24]>ClCC(Cl)(Cl)Cl.C(OCC)(=O)C.ClCCl>[OH:16][C:17]1[C:18]([CH3:24])=[C:19]([OH:23])[CH:20]=[CH:21][C:22]=1[C:8]([C:7]1[CH:11]=[CH:12][CH:13]=[CH:14][C:6]=1[C:5]([OH:10])=[O:15])=[O:9]
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).
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