Synthesis of some benzo[c][2, 6]naphthyridin-5-ones and new tetracyclic benzofuro[4, 5-c]-2, 6-naphthyridin-5(6H)-ones

A series of novel methylbenzofuro[4,5-c]-2,6-naphthyridin-5(6H)-ones were syntesised,first building the pyridine nucleus on the appropriate quinolin- 2-ones,and then condensing the furan ring on the preconstituted benzonaphthyridinones. The benzo[c][2,6]naphthyridinic nucleus was also interesting for its known pharmacological properties,as well as intermediate for the synthesis of natural product analogues.