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. SEM analysis of the isolated material from the reaction supports a 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 DFT 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 of further effective substrates in these types of transformations.