Theoretical study with DFT on the mechanism of visible light-driven β-functionalization of aldehydes

Abstract We present results of density functional theory (DFT) study on the mechanism of photo-organocatalytic β-functionalization of aldehydes with Michael acceptors. The plausible mechanism afforded involves three distinct steps: radical generation, radical addition, oxidative hydrogen atom transfer. The region-determining step is the radical addition step which affords α- or β-radical addition adduct through α-/β-transition states with different barrier. In the reduction step of radical addition adduct, the calculation results support our proposal that oxidative hydrogen atom transfers (HAT) from enamine to the radical addition adduct, generates a neutral intermediate and β-enaminylradical, the latter of which thereafter participates in the previous step of radical addition to form β- intermediate. Our result is in satisfactory accordance with the experimental observation.