The 2-chloro-3-formyl quinoline derivatives (1a-e) on treatment with acetic anhydride and sodium acetate, afforded the corresponding novel 2-oxo-pyrano(2,3-b) quinoline derivatives (2a-e), and these were subjected to ammonia treatment to yield the corresponding naphthyridine derivatives (3a-e). The prepared compounds (2a-e) were tested for their antimalarial, diuretic, clastogenic and antimicrobial properties. Not all the compounds showed a diuretic effect and the significant increase in the frequency of micronuclei shows that they are non-clastogens, whereas the 7-chloro derivative (2e) was a very effective antimalarial agent against the mosquito species. All the compounds were found to have optimum antimicrobial activity against Staphylococcus aureus, Escherichia coli and Salmonella typhi. Compounds 2d and 2e were found to be most active against the bacteria tested.