Acetic Acid → 2,6-Dichloro-2',3'-dihydroxy-4'-methoxy-6'-methyl-benzophenone

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A mixture of 2,6-dichloro-2',3',4'-trimethoxy-6'-methyl-benzophenone (1.78 g; 5 mmol) hydrobromic acid (7.5 ml; 30% in acetic acid) and acetic acid (7.5 ml) is stirred at 75° C. for 2 hours. Water is added and the mixture extracted with methylenechloride. The extract is washed with water and shaken with 2N sodium hydroxide. The alcaline solution is acidified with hydrochloric acid, the separated compound dissolved in methylenechloride and the solution washed with water. After evaporation of the solvent purification is carried out by chromatography (flash column, filled with 36 g of silicagel; elution with 500 ml of petrolether/ethylacetate (4:1; v/v) and 250 ml of petrolether/ethylacetate (1:1; v/v)). The fraction containing the compound is concentrated, the compound crystallized. The yellow crystalls are washed with petrolether and sucked off; 0.64 g (39% y), mp. 182° C.

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