Theoretical Mechanistic Study of C(sp3)−C(sp2) Cross‐Coupling by Photoredox‐Mediated Iridium(III)/Nickel(II)/Quinuclidine Triple Catalysis

Abstract The photoredox‐mediated iridium(III)/nickel(II)/3‐acetoxyquinuclidine triple‐synergistic catalysis was comprehensively investigated by taking a C( sp 3 )−C( sp 2 ) bond cross‐coupling as a reaction model using density functional theory (DFT) calculations. The synergistic mechanism of the triple catalytic system includes a reductive quenching cycle (Ir III −*Ir III −Ir II −Ir III ), an organocatalytic cycle, and a nickel catalytic cycle (Ni II −Ni I −Ni III −[Ni III ] ⊖ −Ni II ). Electronic process analysis shows that 3‐acetoxyquinuclidine acts as a hydrogen atom transfer (HAT) catalyst to regioselectively provide α‐carbon centered radical. Due to more favorable oxidative addition of C−Br to Ni(I) than HAT to avoid the formation of stable Ni(II) species, the generated α‐carbon centered radical prefers to be captured by oxidative addition product Ni(III) to form an unusual [Ni III ] ⊖ C ⊕ species when 3‐acetoxyquinuclidine was employed. These theoretical insights not only provide deep electronic process understanding of the photoredox‐mediated iridium(III)/nickel(II) synergistic catalysis, but also clarify the electron‐withdrawing group effect of quinuclidine, which has a potential guiding role for further development of new cross‐coupling reactions.