Computational Insights into Palladium/Boron-Catalyzed Allylic Substitution of Vinylethylene Carbonates with Water: Outer-Sphere versus Inner-Sphere Pathway and Origins of Regio- and Enantioselectivities
Hongli Wu, Lingfei Hu, Yu Shi, Zhen Shen, Genping Huang
Abstract
Palladium/boron-catalyzed allylic substitution of vinylethylene carbonates with water provides a powerful approach for the enantioselective synthesis of the tertiary C–O bond. Density functional theory calculations in the present work show that the nucleophilic attack via a distinctive type of chelation-assisted inner-sphere pathway is responsible for the experimentally observed regio- and enantioselectivities. The chelation between the hydroxyl group of the boronate moiety and the Pd center in the nucleophilic attack enables the exclusive branched-regioselectivity. The enantioselectivity was rationalized in terms of the lone pair---π repulsive interaction between the O atom of the chelated hydroxyl group and the phenyl ring of the ligand.