Theoretical investigation on the regioselectivity of Ni(COD)2-catalyzed [2 + 2 + 2] cycloaddition of unsymmetric diynes and CO2

• Reaction mechanisms were studied with DFT calculations.
• Regioselectivity of the reaction has been elucidated.
• Explained the inaccessible path involving oxidative coupling of the two CC bonds.

Reaction mechanisms of the Ni(COD)2-catalyzed [2 + 2 + 2] cycloaddition of unsymmetric diynes and CO2 have been theoretically studied by using the density functional theory calculations. Three major steps are included, oxidative coupling of CO2 with Et-substituted CC bond, the second CC bond insertion and reductive elimination of the product from the Ni center, in which the CC bond insertion was found to be rate-determinant. The steric arrangement of the N,P-bidentate ligand was demonstrated to be influential on reaction barriers. Based on the mechanistic study, the regioselectivity of the catalytic reaction was elucidated. In addition, we also explained why the mechanisms involving oxidative coupling of both the CC bonds are unavailable.

The reaction mechanisms and the regioselectivity of the Ni(COD)2-catalyzed [2 + 2 + 2] cycloaddition of unsymmetric diyne and CO2 were studied using density functional theory calculations.Figure optionsDownload as PowerPoint slide