Palladium‐Catalyzed Domino Process to Construct 2,3,9,9a‐tetrahydro‐1h‐fluorene Derivatives:Transient Σ‐alkylpalladium(ii) Complex Mediated C(sp2)‐H Bond Activation

A palladium‐catalyzed cascade reaction involving domino Heck/intramolecular C−H arylation to construct 2,3,9,9a‐tetrahydro‐1H‐fluorene derivatives was developed. Products are obtained in moderate to excellent yields. The transient σ‐alkylpalladium(II) complex is the key intermediate, which mediates the C(sp2)‐H bond activation via a six‐metallacycle. According to a transient σ‐alkylpalladium(II) complex, the control experiment demonstrates that β‐H elimination is faster than C−H activation. The methodology shows high chemoselectivity and good functional group tolerance.