Deaminative radical reactions via relayed proton-coupled electron transfer

Abstract

The deaminative radical reaction is a powerful strategy for efficient radical generation and transformation, but the detailed mechanism still remains unclear. Herein, the possible mechanisms of a series of deaminative radical reaction models have been constructed and investigated systematically in theory. Remarkably different from the generally accepted single-electron transfer (SET) mechanism for radical generation in deaminative reactions, the relayed proton-coupled electron transfer (relayed-PCET) has been discovered in these reactions. Subsequent N–X (XC, O, N et al.) bond breaking via homolysis, rather than heterolysis, leads to the formation of various kinds of deaminative radicals, including alkyl radicals, trifluoromethyl radicals, N-centered radicals, O-centered radicals, and other related radicals. The exact orbital overlap pictures associated with different interaction (i.e., π–π* and lone pair–π*) modes have been discovered and captured for discovering the nature of these deaminative radical reaction processes, and electron localization function (ELF) analysis proved that a pair of electrons move from the N–X (XC, O, N) bond center to both two atoms via a homolysis cleavage process. This work should be critical for understanding the general principle and detailed mechanism of deaminative radical reactions.