Diversity Synthesis of Pyrimido[4,5-b][1,6]naphthyridine and Its Derivatives under Microwave Irradiation

A series of new heterocyclic compounds, involving pyrimido[4,5-b][1,6]-, benzo[b][1,6]-, pyrazolo[3,4-b][1,6]naphthyridine, and aza-benzo[b]fluorene skeletons were successfully synthesized via the reaction of structurally diverse 3,5-dibenzylidenepiperidin-4-one with various enamine-likes (2,6-diaminopyrimidin-4(3H)-one, 3-amino-5,5-dimethylcyclohex-2-enone, 3-methyl-1-phenyl-1H-pyrazol-5-amine and 1H-benzo-[d]imidazol-2-amine) in glycol under microwave irradiation. This method has the advantages of short synthetic route, operational simplicity, and increased safety for small-scale fast synthesis for biomedical screening.