AbstractThe cyclization ofm‐substituted anilinomethylenemalonates (1) in the presence of polyphosphate ester and some other cyclizing agents gave mixtures of the isomeric ethyl 5‐ (2) and 7‐substituted 4‐hydroxy‐3‐quinolinecarboxylates (3), which led to mixtures of the corresponding quinolinecarboxylic acids (4and5) by hydrolysis. The proportions of4and5in the mixtures were determined on the basis of their nmr spectra. Novel 5‐chloro‐ (8a), 5‐methyl‐ (8b) and 5‐nitro‐1‐ethyl‐1,4‐dihydro‐4‐oxo‐3‐quinolinecarboxylic acids were prepared and evaluated for antimicrobial activities. No sig