Shuttle HAT for mild alkene transfer hydrofunctionalization

Hydrogen atom transfer (HAT) from a metal-hydride is a reliable and powerful method for functionalizing unsaturated C–C bonds in organic synthesis. Cobalt hydrides (Co–H) have garnered significant attention in this field, where the weak Co–H bonds are most commonly generated in a catalytic fashion through a mixture of stoichiometric amounts of peroxide oxidant and silane reductant. Here we show that the reverse process of HAT to an alkene, i.e. hydrogen atom abstraction of a C–H adjacent to a radical, can be leveraged to generate catalytically active Co–H species in a new application of shuttle catalysis coined shuttle HAT. This method obviates the need for stoichiometric reductant/oxidant mixtures thereby greatly simplifying the generation of Co–H under exceedingly mild reaction conditions. This approach opens the door for the introduction of functional handles (e.g., iodides) that were previously inaccessible through other catalytic approaches, and paves the way for new reagent design which incorporates this shuttle HAT platform. To demonstrate the generality of this shuttle HAT platform, five different reaction manifolds are shown, including the late-stage C(sp3) iodination of structurally diverse FDA approved drugs.