[Cl-].[Al+3].[Cl-].[Cl-].[Cl:5][C:6]1[CH:11]=[CH:10][C:9]([CH2:12][C:13](Cl)=[O:14])=[CH:8][CH:7]=1.[F:16][C:17]1[C:22]([F:23])=[CH:21][CH:20]=[CH:19][C:18]=1[OH:24]>ClCCCl.O>[Cl:5][C:6]1[CH:11]=[CH:10][C:9]([CH2:12][C:13]([C:19]2[CH:20]=[CH:21][C:22]([F:23])=[C:17]([F:16])[C:18]=2[OH:24])=[O:14])=[CH:8][CH:7]=1A mixture of aluminium chloride (7.66 g, 57.4 mmol, 1.5 eq.) and (4-chlorophenyl)acetyl chloride (8.7 g, 46 mmol, 1.2 eq.) in 1,2-dichloroethane (75 ml) is stirred at 0° C. for 30 min. A solution of 2,3-difluorophenol (5 g, 38.4 mmol) in 1,2-dichloroethane (25 ml) is added to the reaction mixture, which is heated in an oil bath at 90° C. overnight. The reaction mixture is cooled to room temperature, diluted with water and extracted with ethyl acetate. The organic phase is dried over anhydrous magnesium sulfate, filtered and evaporated to dryness in vacuo to afford a brown solid. This is triturated with hexane/ethyl acetate (9:1), filtered and dried to afford the title compound as a pale brown fine solid which is 87% pure by HPLC analysis.
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