Rh/Cu-Catalyzed Cascade [4+2] Vinylic C-H O-Annulation and Ring Contraction of α-Aryl Enones with Alkynes in Air.

An unprecedented Rh-catalyzed ketone-directed vinylic C-H activation/[4+2] O-annulation of α-aryl enones with internal alkynes followed by a Cu-catalyzed ring contraction in air to provide multiaryl-substituted furan derivatives has been developed. The preliminary mechanism study identifies the active pyrylium salt as the key intermediate.