Computational Study on the Mechanism and Origin of the Regioselectivity and Stereospecificity in Pd/SIPr-Catalyzed Ring-Opening Cross-Coupling of 2-Arylaziridines with Arylboronic Acids

Abstract

The mechanism, regioselectivity, and stereospecificity of Pd/NHC-catalyzed ring-opening cross-coupling of 2-arylaziridines with arylboronic acids (Takeda et al. J. Am. Chem. Soc. 2014, 136, 8544−8547) is rationalized from density functional theory calculations. Pd(0)SIPr complex, the active species, can be formed through the reduction of (η3-cinnamyl)(Cl)Pd(II)SIPr complex, where arylboronic acid in solution plays a key role. Then the Pd(0)SIPr complex acts as the active species of the catalytic cycle that consists of the regioselective and stereospecific oxidative addition, proton transfer, rate-determining transmetalation, and reductive elimination. Transition states for the oxidative addition were systematically determined from a multicomponent artificial force induced reaction search and explained the regioselectivity and stereospecificity of the reaction. An energy decomposition analysis on the key transition states suggested that the interactions between Pd(0)SIPr and 2-arylaziridines are important to the selectivity. The computed mechanism of the full catalytic cycle is consistent with the experimental data. Our detailed mechanistic survey provides important mechanistic insights for enantiospecific and regioselective ring-opening reactions of 2-arylaziridines.