Process for the preparation of fluoroquinolonecarboxylic acids

Abstract

Fluoroquinolonecarboxylic acids can be prepared by hydrolysis of the corresponding C1-C4-alkyl esters with addition of water, acetic acid, and sulfuric acid using a drastically reduced amount of sulfuric acid if, relative to 1 mol of C1-C4-alkyl fluoroquinolonecarboxylate, less than 30 g of sulfuric acid are employed, the reaction mixture is heated to reflux for 0.5 to 8 hours, then a mixture of acetic acid, C1-C4-alkyl acetate, C1-C4-alkyl alcohol, and optionally water is distilled off, and finally the fluoroquinolonecarboxylic acid prepared is isolated.

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