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. First rhodium, then copper: An unprecedented cascade reaction consisting of a Rh‐catalyzed ketone‐directed vinylic C−H [4+2] O‐annulation of α,β‐enones with alkynes and a subsequent Cu‐catalyzed ring contraction in air to form multiaryl‐substituted furan derivatives is realized. The pyrylium salt is identified as the key intermediate.