Acetic Acid → 5,7-Dichloro-6-fluoro-1-(2,4-difluorophenyl)-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid

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Reaction Steps

41.6 g of ethyl 5,7-dichloro-6-fluoro-1-(2,4-difluorophenyl)-1,4-dihydro-4-oxo-3-quinolinecarboxylate are heated under reflux with 250 ml of acetic acid, 200 ml .of water and 28.5 ml of concentrated sulphuric acid for 3 hours. After cooling, the mixture is poured into 2 liter of ice-water and the precipitate is filtered off with suction, washed with water and dried. 35.5 g of 5,7-dichloro-6-fluoro-1-(2,4-difluorophenyl)-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid are obtained, melting point: 244°-246° C.

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