Unveiling the dual activation effect of NHC-catalyst in an asymmetric reaction system†

Abstract

Dual activation has become an attractive methodology in organocatalysis and has been employed as an effective strategy to achieve enantioenrich products from asymmetric catalysis. We propose an interesting mechanistic reaction, which utilized a chiral NHC-catalyst to control facial selectivity between NHC-bonding enolate and NHC non-covalent bonding Michael acceptor. However, the detailed effect of NHC-catalysts and the origin of chemo- and stereoselectivity still need further explanation. To illustrate the details of the mechanism, we herein employed density functional theory (DFT) to reveal the origin of chemoselectivity and stereoselectivity, which was determined by reaction kinetic control and the effect of dual activation by NHC-catalyst, respectively. We hope that this theoretical calculation could help chemists predict and design novel dual activation reactions to construct important and useful building blocks.