Kinetic Resolution of 2-Cinnamylpyrrolines Enabled by Photoexcited Chiral Copper Complex-Mediated Alkene E → Z Isomerization

The two-dimensional (2D) stereochemical information transformed into three-dimensional (3D) chemical space through stereospecific reactions is expansive in the discovery of biologically or pharmacologically active molecules. Alkene subunits are ubiquitous structural motifs and constitute diverse and inexpensive start points for this endeavor. Herein, a kinetic resolution enabled by photoexcited chiral copper complex-mediated alkene E → Z isomerization is disclosed, leading to enantiodivergent synthesis of 2-cinnamylpyrrolines. Mechanistic experiments and density functional theory (DFT) calculations gave reasons for the observed kinetic resolution efficiency, which is the cooperative result of the different association abilities between two enantiomers and the chiral copper complex (ground-state thermodynamics) and the different overall sensitization rates of the substrate–catalyst complex (excited-state kinetics). This revitalized protocol of kinetic resolution has shown wide functional group compatibility to explore 3D chemical space, which brings another level of advance and complementarity to the ingenious control of stereochemistry in triplet-state photoreactions.