DFT Mechanistic Insights into the Ni(II)-Catalyzed Enantioselective Arylative Cyclization of Tethered Allene-Ketones

Density functional theory (DFT) has provided a detailed mechanistic picture for the redox neutral nickel(II)-catalyzed arylative cyclization reactions of a tethered allene-ketone with arylboronic acids. A mechanistic rationale for the high diastereo- and enantioselectivity achieved experimentally at high reaction temperature was uncovered through modeling the reaction with a chiral ligand and the predicted stereochemical outcome corroborates with experimental results. An unprecedented mechanism for the base-free organoboron transmetalation was revealed and the regioselectivity of migratory insertion of tethered allene-ketones as well as the stability of the possible allylnickel isomers (s-allyl vs p-allyl) were clarified. The multifaceted nature of the reaction is revealed with certain elementary steps preferring cationic compared to the neutral state.

Automated summary

Density functional theory has been used to elucidate the mechanistic details of arylative cyclization reactions with arylboronic acids. The modeling results are in agreement with experimental observations and explain the high diastereo- and enantioselectivity at high reaction temperature. Additionally, a novel mechanism for base-free organoboron transmetalation has been revealed.