Sulfuric Acid → 2-[2-(4'-Chloro-biphenyl-4-YL)-2-oxo-ethyl]acrylic acid

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193.3 g (1.45 mol) of anhydrous aluminum chloride are introduced in 1100 g of o-dichlorobenzene and the mixture is brought to 45° C. with stirring. A solution of 80.9 g (0.72 mol) of itaconic anhydride and 132 g (0.7 mol) of 4-chlorobiphenyl in 700 g of o-dichlorobenzene at 50° C. is added dropwise in the course of three hours. The reaction mixture is stirred at 25° C. for four hours and then added to an ice-cold mixture of 1000 g of water and 25 g of sulfuric acid (96%). The aqueous phase is separated off. The organic phase is washed three times with a mixture of 1000 g of water and 15 g of sulfuric acid (96%) in each case. After washing three times, it is allowed to cool to approximately 20° C. and the colorless product is then filtered off with suction. This is then washed three times with 150 g of ethanol (96%) in each case. The product is dried at 60° C. and about 100 mbar until free of solvent and water. 148 g (0.49 mol) of 4-(4′-chlorobiphenyl-4-yl)-4-keto-2-methylenebutyric acid (70%) are obtained as a colorless, finely crystalline powder. By working up the mother liquor, as described in Example 1, the yield is increased to 83%. (HPLC purity 99.6-99.8%)

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