Microwave-assisted Domino Cyclization for the Synthesis of Novel Spiro-benzo[a] phenazine Annulated Heterocycles Catalyzed by a Basic Ionic Liquid

An efficient and green strategy for the improved synthesis of a biologically and pharmaceutically interesting multi-functionalized diverse novel spiro-benzo[a] phenazine annulated heterocycles was developed with the assistance of microwave irradiation. A sequential one-pot, two-step domino reaction starting from 2-hydroxynaphthalene-1,4-dione, benzene-1,2-diamines, a cyclic carbonyl compound, and 1,3-indandione in the presence of a basic ionic liquid (1-butyl-3-methylimidazolium hydroxide) as an expedient, ecofriendly and reusable catalyst afforded the corresponding novel spiro[benzo[a] indeno[20,10: 5,6] pyrano[2,3-c] phenazine] derivatives with high yield under solvent-free conditions. This domino Knoevenagel-Michael annulation reaction provided five new bonds (two C=C, two CN, and one C-O) and two new rings through multiple operations in a single flask.