Merging Photochemical Olefin Metathesis with an Amination Reaction

A merger of photochemical olefin metathesis and C–H amination enables us to unlock a rare protocol for the synthesis of functionalized olefins. Our method allows for the stereoselective generation of enamines using a mild and bench-stable oxime ester precursor as the N-linchpin. The key feature is the multitasking catalysis of fac-Ir(ppy)3, which not only enables the energy transfer (EnT) mediated N–O bond cleavage of an oxime ester to produce an N-centered radical (NCR) and a benzoyloxy radical (•OBz) but also promotes the cycloaddition of two styrene moieties to form a cyclobutane analogue at different stages of the reaction. Further, mechanistic investigations and DFT calculations provide crucial insights on a rare ring-opening metathesis, prompted by the oxidation of the cyclobutane intermediate, followed by nucleophilic attack of an in situ generated benzoate anion (−OBz) and radical-coupling with NCR leading to a highly stable singlet intermediate that undergoes sequential N-protonation and single electron reduction to effectuate elimination and regeneration of •OBz, delivering the Z-selective aminated stilbene. Reasonable functionality tolerance, in addition to satisfactory yield and exclusive stereoselectivity are the salient features of this newly discovered methodology.