Mechanistic studies: Comparative investigation of nickel(0)-catalyzed selective decarbonylative cross-coupling of cyclic anhydrides with alkyl bromides or aryl triflates

The mechanisms of the nickel-catalyzed decarbonylative cross-coupling of cyclic anhydrides with alkyl bromides, and the nickel-catalyzed non-decarbonylative cross-coupling of cyclic anhydrides with aryl triflates are investigated using density functional theory (DFT) calculations. The results show that the decarbonylative reaction has a radical-involved mechanism with cyclic anhydrides being activated first by the nickel catalyst. The Ni center undergoes a valence change of Ni(0)-Ni(II)-Ni(III)-Ni(I)-Ni(II)-Ni(0). While the non-decarbonylative reaction has a double oxidative addition mechanism with aryl triflates being activated first by the nickel catalyst. The Ni center undergoes a valence change of Ni(0)-Ni(II)-Ni(I)-Ni(III)-Ni(I)-Ni(0). The reasons that affect the selective decarbonylation of the coupling products of cyclic anhydrides are explained from the perspective of substrate activation priority and key intermediate geometric structure. These theoretical insights may shed light on the understanding and development of transition-metal-catalyzed selective decarbonylative C-O bond activation reactions.