Selective construction of functionalized chromeno[3,4-b]pyrroles and benzo[c]chromenes via a K3PO4 promoted three-component reaction

Abstract

An efficient and convenient synthetic protocol for functionalized chromeno[3,4-b]pyrroles was successfully developed through a K₃PO₄ promoted three-component reaction of pivaloylacetonitrile (benzoylacetonitrile), dialkyl but-2-ynedioates and 2-aryl-3-nitrochromenes in refluxing ethyl acetate. A similar three-component reaction of malononitrile, dialkyl but-2-ynedioates and 2-aryl-3-nitrochromenes resulted in polysubstituted benzo[c]chromene derivatives in good yields. Plausible reaction mechanisms for selective formation of two annulated chromanes were rationally proposed.