[OH:1][C:2]1C=C(C=C(C)C=1)C(O)=O.[C:12](=[O:15])([O-])[O-:13].[K+].[K+].[CH3:18]I.CN([C:23]1[CH:28]=[CH:27][CH:26]=[CH:25]N=1)C.[CH3:29][C:30](C)=O>>[CH3:2][O:1][C:26]1[CH:27]=[C:28]([CH:23]=[C:29]([CH3:30])[CH:25]=1)[C:12]([O:13][CH3:18])=[O:15]To acetone (180 mL) were added 3-hydroxy-5-methylbenzoic acid (9 g, 59.16 mmol), potassium carbonate (33 g, 237 mmol) and methyl iodide (37.2 mL, 591.6 mmol). For O-methylation, the resulting mixture was heated at 65° C. for 12 hours in the presence of a catalytic amount of dimethylaminopyridine. After vacuum distillation of the acetone, the concentrate was treated in water (300 mL) and dichloromethane (450 mL). The organic layer was dried over anhydrous magnesium sulfate and subjected to distillation. Column chromatography (silica gel, ethyl acetate-hexane 1:12 v/v) with the residue produced the title compound as a colorless liquid (9.98 g, 93.5%).
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