Synthesis of new pyrazolo[4,3‐ c ]quinolin‐3‐one derivatives and some oxazolo[4,5‐ c ]quinoline‐2,4‐diones

The new pyrazolo[4,3‐ c ]quinolin‐3‐one derivatives 3a‐c and 6a‐c were prepared by the following three steps: first the preparation of ethyl 4‐hydroxyquinoline‐3‐carboxylate derivatives 1 and 4 by reaction of isatoic anhydrides and ethyl malonate and ethyl acetoacetate respectively, then chloration of 1 and 4 with phosphorus oxychloride to give 2 and 5 and finally the condensation of 2 and 5 with hydrazine and its derivatives. In addition, the successful synthesis of oxazolo[4,5‐ c ]quinoline‐2,4‐diones 9a‐f are reported.