The synthesis of three new heterocycles: the pyrido[4,3 or 3,4 or 2,3-c]-1,5-naphthyridines

Pyrido[4,3 or 3,4 or 2,3-c]-1,5-naphthyridines were obtained with good yields after chlorodehydroxylation and dehalogenation reactions starting from the parent pyridonaphthyridinones. These pyridonaphthyridinones were synthesized in a two-step procedure using a Suzuki cross-coupling reaction between 2-chloro-3-fluoropyridine and orthocyanopyridylboronic esters followed by a KOH-mediated anionic ring closure.