The rate of the nucleophilic displacement of the fluoro atom of 7-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylate could be enhanced either by the introduction of further fluoro atom(s) into position(s) 6 and/or 8, or by the formation of a boron chelate (e.g. 3). The regioselectivity of the nucleophilic substitution of the chloro atom in 1-substituted 6-fluoro-7-chloro-4-oxo-1,4-dihydroquinoline-3-carboxylic acids could also be enhanced by the formation of a boron chelate (e.g. 7).