Condensation of ethyl 2,4,5-trifluorobenzoylacetate (I) with triethyl orthoformate in refluxing Ac2O produced the benzoyl ethoxyacrylate (II), which was further condensed with 2-amino-5-fluoropyridine (III) to afford enamine (IV). Cyclization of (IV) in the presence of K2CO3 gave rise to the quinolone (V). The 7-fluoride group of (V) was then displaced by N-methylpiperazine (VI) in cold pyridine to furnish the piperazinyl quinolone (VII). Finally, ester hydrolysis in (VII) under acidic conditions yielded the target compound. In a closely related procedure, ester (V) was hydrolyzed to acid (VIII) using HCl. Subsequent displacement of the 7-fluoride of (VIII) with N-methylpiperazine (VI) provided the desired piperazinyl quinolone.

Condensation of ethyl 2,4,5-trifluorobenzoylacetate (I) with triethyl orthoformate in refluxing Ac2O produced the benzoyl ethoxyacrylate (II), which was further condensed with 2-amino-5-fluoropyridine (III) to afford enamine (IV). Cyclization of (IV) in the presence of K2CO3 gave rise to the quinolone (V). The 7-fluoride group of (V) was then displaced by N-methylpiperazine (VI) in cold pyridine to furnish the piperazinyl quinolone (VII). Finally, ester hydrolysis in (VII) under acidic conditions yielded the target compound. In a closely related procedure, ester (V) was hydrolyzed to acid (VIII) using HCl. Subsequent displacement of the 7-fluoride of (VIII) with N-methylpiperazine (VI) provided the desired piperazinyl quinolone.