Pyrano[2,3-b]quinolin-2-ones have been synthesized efficiently from 2-chloro-3-formylquinolines in a single step by treating
with sodium acetate and acetic acid under microwave irradiation. The structures of the compounds have been established by IR,
NMR and mass spectral data. Unexpectedly, 3-formylquinolin-2(1H)-ones were exclusively formed in very high yields by
changing the molar ratio of acetic acid and sodium acetate in just 1.5 to 2.5 min.