Time-Resolved EPR Revealed the Formation, Structure, and Reactivity of N-Centered Radicals in an Electrochemical C(sp3)-H Arylation Reaction

Electrochemical synthesis has been rapidly developed over the past few years, while a vast majority of the reactions proceed through a radical pathway. Understanding the properties of radical intermediates is crucial in the mechanistic study of electrochemical transformations and will be beneficial for developing new reactions. Nevertheless, it is rather difficult to determine the live radical intermediates due to their high reactivity. In this work, the formation and structure of sulfonamide N-centered radicals have been researched directly by using the time-resolved electron paramagnetic resonance (EPR) technique under electrochemical conditions. Supported by the EPR results, the reactivity of N-centered radicals as a mediator in the hydrogen atom transfer (HAT) approach has been discussed. Subsequently, these mechanistic study results have been successfully utilized in the discovery of an unactivated C(sp(3))-H arylation reaction. The kinetic experiments have revealed the rate-determined step is the anodic oxidation of sulfonamides.

Automated summary

Electrochemical synthesis has rapidly developed in recent years, with the majority of reactions proceeding through a radical pathway. Understanding the properties of radical intermediates is crucial for mechanistic studies and developing new reactions. This study directly researched the formation and structure of sulfonamide N-centered radicals using the time-resolved EPR technique under electrochemical conditions, and successfully applied the results in the discovery of an unactivated C(sp(3))-H arylation reaction.