Copper-Catalyzed Three-Component Photo-ATRA-Type Reaction for Asymmetric Intermolecular C-O Coupling

Atom transfer radical addition (ATRA) reaction of alkenes has had a tremendous impact on the field of radical difunctionalizations of alkenes. Particularly in the three-component photo-ATRA-type processes, a rich chemical space and structural diversity could be achieved by smart combination of redox-active radical precursors and the third coupling components (e.g., halides, C-, N-, and O-nucleophiles) under mild con-ditions. However, the inherent complicated mechanisms involving radical chain or outer-sphere SET of the incipient radical intermediates render dearth of general catalytic methods for highly enantioselective variants, especially these regarding asymmetric intermolecular C-O bond formation. Here, we report a visible-light-induced copper-catalyzed asymmetric three-component photo-ATRA-type reaction of alkenes with oxime esters and carboxylic acids. In this process, a highly enantioselective intermolecular C-O cross-coupling between incipient sp3-hybridized carbon radicals and carboxylic acids was enabled by aryl π-bond-engaged [σ + π]-copper complex. This three-component photo-ATRA-type reaction exhibits broad substrate scope and high functional group tolerance with respect to each component, giving the desired cross-coupled products with generally good yields and excellent enantioselectivity (>70 examples; up to 97% ee). Combined experimental and computational studies are also performed to gain insight into the mechanism. This finding provides a new platform for the development of other enantioselective benzylic-type radical-based cross-coupling reactions.