Mechanism and Selectivities of [Cu]/[M] (M=Pd, Ni) Synergistic Catalyzed Alkene Arylboration: A DFT Investigation

The transition metal–catalyzed boronation reactions are considered as one of the most effective methods for the synthesis of alkylboranes in terms of functional group compatibility and reactivity. Herein, the mechanism of synergistic catalysis of alkene arylboration by [Cu]/[M] (M=Pd, Ni) bimetallic catalysts, as well as the regioselectivity and stereoselectivity of the reactions, has been investigated by using DFT calculations. The results show that four processes are involved in the whole reaction: [Cu]-catalyzed borylcuprization of alkene, [Pd] or [Ni]-catalyzed oxidative addition of halogenated aryl groups, transmetalation, and reductive elimination. [Cu]/[Ni] bimetallic catalysts show the same catalytic activity as [Cu]/[Pd] catalysts and are good economic alternatives for the alkene arylboration. The cleavage of B–B bond of B₂Pin₂ is the rate-determining step. The regioselectivity of the title reaction is determined by the mode of the alkene insertion into the Cu–B bond. The attacking of C atom with the more electron-rich character in alkyne makes for the formation of the main product. The small energy barrier difference between the rotation of the Cu-C σ bond from the syn-9 to the anti-9 controls the stereoselectivity. Our findings provide a thorough explanation of the experimental results and shed light on the further development of the alkene functionalization.