8. Catalytic Olefin Hydroamidation Enabled by Proton-Coupled Electron Transfer

David C. Miller, Gilbert J. Choi, Hudson S. Orbe, Robert R. Knowles:

https://pubs.acs.org/doi/full/10.1021/jacs.5b09671

ABSTRACT: Here we report a ternary catalyst system for the intramolecular hydroamidation of unactivated olefins using simple N-aryl amide derivatives. Amide activation in these reactions occurs via concerted proton-coupled electron transfer (PCET) mediated by an excited state iridium complex and weak phosphate base to furnish a reactive amidyl radical that readily adds to pendant alkenes. A series of H-atom, electron, and proton transfer events with a thiophenol cocatalyst furnish the product and regenerate the active forms of the photocatalyst and base. Mechanistic studies indicate that the amide substrate can be selectively homolyzed via PCET in the presence of the thiophenol, despite a large difference in bond dissociation free energies between these functional groups.