Synthesis and in vitro biological activity of some 7-[hydrazino], -[hydrazonyl] and -[pyrazolyl]quinolone-3-carboxylic acids

1-Ethyl-6-fluoro-7-hydrazino-1,4-dihydro-4-oxoquinoline-3-carboxylic acid (8) has been prepared and served as a versatile intermediate from which a number of hydrazone, pyrazole and dihydropyridazine derivatives were synthesized. The in vitro biological activity of some of these derivatives is reported.