Divergent Concerted Proton–Electron Transfer (CPET) and Hydrogen Atom Transfer (HAT) Pathways of Amidyl Radical Reactivity Enable Chemoselective Functionalization

Amidyl radicals mediate a diverse array of intermolecular aliphatic C(sp³)-H and decarboxylative functionalizations. Interestingly, we have observed that decarboxylative processes proceed with excellent chemoselectivity even with substrates containing weak C(sp³)-H bonds. Herein, we report a mechanistic basis for understanding this high chemoselectivity of amidyl radicals through divergent reaction pathways. A computational assessment of the transition state SOMOs and intrinsic bonding orbitals for amidyl radical hydrogen atom transfer (HAT) and concerted proton-electron transfer (CPET) processes support a shift in mechanism between aliphatic C(sp³)-H or carboxylic acid O-H abstraction, which is supported by experimental studies. These findings provide a rationale for the chemoselectivity of decarboxylative reactions mediated by amidyl radicals.