Synthesis of Indene Frameworks via Rhodium-Catalyzed Cascade Cyclization of Aromatic Ketone and Unsaturated Carbonyl Compounds

A novel rhodium(III)-catalyzed direct functionalization of the ortho-C–H bond of aromatic ketone derivatives and an intramolecular cyclization sequence produced indene derivatives in moderate to good yields. This cascade cyclization involves a conjugate addition of α,β-unsaturated ketone and subsequent aldol condensation. The reaction occurred efficiently in the presence of water and under an atmosphere of air.