The starting materials for the present invention are known, or if new, may be prepared from known materials by known means. Thus, ethyl 1-cyclopropyl-6,7,8-trifluoro-1,4-dihydro-4-oxo-3-quinolinecarboxylate is prepared as described in Belgian Pat. No. 899,399 or No. DE3318145. Alternatively, it may be prepared by a series of reactions starting from 2,3,4,5-tetrafluorobenzoic acid. The sodium salt of 2,3,4,5-tetrafluorobenzoic acid is reacted with oxalyl chloride and the product condensed with diethyl malonate in the presence of magnesium turnings to afford after hydrolysis 2,3,4,5-tetrafluorobenzoylacetic acid, ethyl ester. This compound is, in turn, treated with triethylorthoformate and acetic anhydride, followed by cyclopropylamine to afford 2-(2,3,4,5-tetrafluorobenzoyl)-3-cyclopropylamino acrylic acid, ethyl ester, which is then ring closed to give the desired starting material. The corresponding methyl ester is prepared using dimethylmalonate in the sequence described above.
