A Sequential Activation of Alkyne and C–H Bonds for the Tandem Cyclization and Annulation of Alkynols and Maleimides through Cooperative Sc(III) and Cp-Free Co(II) Catalysis

[4 + 2] oxidative Diels–Alder reaction of readily available alkynols with maleimide is achieved for the rapid access of pthalimide-fused multicyclic compounds. The reaction is proposed to go through a sequence of Sc­(OTf)3-catalyzed electrophilic cyclization, ligand exchange with Cp*-free cobalt, and C–H activation followed by maleimide insertion.