Redox-Gated Tertiary Allylic C-H Oxygenation via Photocatalytic Radical-Polar Crossover

We developed a photoredox strategy for the highly regioselective oxygenation of tertiary allylic and propargylic C-H bonds with alcohols or water nucleophiles. The reaction proceeds via a redox-gated radical-polar-crossover pathway, in which intermolecular hydrogen atom transfer generates allylic radicals that are selectively oxidized to carbocations only at tertiary sites, enabling a subsequent C-O bond formation by trapping with oxygen nucleophiles. This approach overrides the inherent preference for less hindered positions in classical metal-catalyzed π-allyl chemistry. The method accommodates internal alkenes, alkynes, and diverse alcohol nucleophiles, including complex bioactive substrates, and enables both intermolecular and intramolecular modes of oxygenation.