An Expanded SET Model Associated with the Functional Hindrance Dominates the Amide-Directed Distal sp3 C-H Functionalization.

Abstract

The mechanistic understanding of catalytic radical reactions currently lags behind the flourishing development of new types of catalytic activation. Herein, an innovative single electron transfer (SET) model has been expanded by using the nonadiabatic crossing integrated with the rate-determining step of 1,5-hydrogen atom transfer (HAT) reaction to provide the control mechanism of radical decay dynamics through calculating excited-state relaxation paths of a paradigm example of the amide-directed distal sp3 C-H bond alkylation mediated by Ir-complex-based photocatalysts. The stability of carbon radical intermediates, the functional hindrance associated with the back SET, and the energy inversion between the reactive triplet and closed-shell ground states were verified to be key factors in improving catalytic efficiency via blocking radical inhibition. The expanded SET model associated with the dynamic behaviors and kinetic data could guide the design and manipulation of visible-light-driven inert bond activation by the utilization of photocatalysts bearing more or less electron-withdrawing groups and the comprehensive considerations of kinetic solvent effects and electron-withdrawing effects of substrates.