[Cl-].[Al+3].[Cl-].[Cl-].[CH3:5][C:6]1[O:10][N:9]=[CH:8][C:7]=1[C:11](Cl)=[O:12].[CH3:14][O:15][C:16]1[CH:21]=[CH:20][CH:19]=[CH:18][CH:17]=1>>[CH3:14][O:15][C:16]1[CH:21]=[CH:20][C:19]([C:11]([C:7]2[CH:8]=[N:9][O:10][C:6]=2[CH3:5])=[O:12])=[CH:18][CH:17]=1A mixture of aluminium chloride (10 g) and 5-methylisoxazole-4-carbonyl chloride (2.7 g) in methoxybenzene (50 ml) was stirred at room temperature for 16 hours. The mixture was quenched with excess ice and extracted with ether (3×200 ml). The combined organic layers were washed with water (3×500 ml), dried (anhydrous magnesium sulphate) and filtered. The filtrate was evaporated to dryness. The residue was purified by chromatography on silica eluted with a mixture of ethyl acetate and cyclohexane (1:10) followed by HPLC on silica eluted with a mixture of ethyl acetate and hexane (1:20) to give 4-(4-methoxybenzoyl)-5-methylisoxazole (compound 18, 0.35 g) as a white solid mp 78°-79° C.
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