Heterogeneous Palladium(0) Catalysts for C(sp³)–H Activation and Coupling to Form Hindered C–C Bonds

Herein, we explore the mechanism of palladium-catalyzed alkylation of tertiary carbon centers predisposed to form captodative radical intermediates. Scanning electron microscopy analysis of the isolated material from the reaction supports heterogeneous palladium as the active catalyst. The reaction can also be carried out with commercially available Pd/C catalysts, which feature a scope including previously failed substrates. A range of mechanism experiments and density functional theory calculations provide support for a catalytic cycle involving heterogeneous palladium. The potential of a favorable Pd(0) oxidative addition to a C–H bond vs a concerted metalation deprotonation from a more oxidized form of palladium is of particular interest. These discoveries provide the impetus to explore additional heterogeneous catalysts in C–H activation and to design further effective substrates in these types of transformations.