Oxidation and Reduction Pathways in the Knowles Hydroamination via a Photoredox‐Catalyzed Radical Reaction

Systematic reaction path exploration revealed the entire mechanism of Knowles's light‐promoted catalytic intramolecular hydroamination. Bond formation/cleavage competes with single electron transfer (SET) between the catalyst and substrate. These processes are described by adiabatic processes through transition states in an electronic state and non‐radiative transitions through the seam of crossings (SX) between different electronic states. This study determined the energetically favorable SET path by introducing a practical computational model representing SET as non‐adiabatic transitions via SXs between substrate's potential energy surfaces for different charge states adjusted based on the catalyst's redox potential. Calculations showed that the reduction and proton shuttle process proceeded concertedly. Also, the relative importance of SET paths (giving the product and leading back to the reactant) varies depending on the catalyst's redox potential, affecting the yield. Systematic exploration of reaction paths based on quantum chemical calculations revealed the entire mechanism of Knowles's light‐promoted catalytic intramolecular hydroamination via radical processes. The energetically favorable reaction path was determined based on the reaction path searches and the SX geometry searches. The present calculations showed that the reduction and proton transfer proceed concertedly.