Multicomponent synthesis of diverse pyrano-fused benzophenazines using bifunctional thiourea-based organocatalyst in aqueous medium.

A series of pyrano-fused benzophenazines were synthesized using a bifunctional thiourea-based organocatalyst from the one-pot four-component reaction of 2-hydroxy-1,4-naphthoquinone, benzene-1,2-diamines, malononitrile or its derivatives and isatins or aromatic aldehydes in aqueous medium. Metal-free reaction condition, water as solvent, high bond forming efficiency (five new bonds formed in one step), good yields and easy purification process are the notable features of this methodology.