Synthesis of 4H-chromenes by an unexpected, K3PO4-mediated intramolecular Rauhut–Currier type reaction

Abstract

In an attempt to develop the umpolung of Michael acceptors using chalcones having an enoate moiety under N-heterocyclic carbene (NHC) catalysis, a K₃PO₄-mediated intramolecular Rauhut–Currier type reaction was observed. This C(sp²)–C(sp²) coupling reaction afforded the biologically important 4H-chromenes in moderate to good yields. It is likely that the enol ether functionality acts as the nucleophilic trigger in this reaction.