Detangle the Competing Sequence of 1e and 2e Oxidative Addition in Nickel(I)‐Catalyzed Radical Coupling Reactions

Nickel‐catalyzed radical coupling reactions with electrophiles provide an intriguing strategy for radical functionalization. This type of reaction consists of two competing oxidative addition steps, i.e., the one‐electron oxidative addition of radical to Ni(I) and the two‐electron oxidative addition of electrophile to Ni(I). The competition outcome unambiguously determines both the optimal reaction mechanism and the enantiocontrol model. Theoretical studies were performed to detangle the competing sequence of one‐electron and two‐electron oxidative addition steps. Computational results revealed that the one‐electron oxidative addition of radical to Ni(I) bromide, followed by 1e reduction to generate alkyl Ni(I) intermediate, occurs preferentially before the two‐electron oxidative addition of electrophile to Ni(I) bromide. The higher reactivity of the alkyl Ni(I) complex compared to Ni(I) bromide in the rate‐determining two‐electron oxidative addition guaranteed the superiority of this Ni I /Ni II /Ni I /Ni III catalytic cycle. The quantitative steric‐electronic effect dissection (QSED) analysis has pinpointed that the more significant charge transfer stabilization is the dominant factor conferring higher reactivity to the alkyl Ni(I) complex. Natural population analysis (NPA) demonstrates that the stronger electron‐donating ability of the alkyl ligand compared to the bromide ligand increases the electron density at the nickel center of alkyl Ni(I), thereby facilitating the charge transfer to the electrophile.