Controlling
of radical reactivity by binding a radical to the metal
center is an elegant strategy to overcome the challenge that radical
intermediates are “too reactive to be selective”. Yet,
its application has seemingly been limited to a few strained-ring
substrates, azide compounds, and diazo compounds. Meanwhile, first-row
transition-metal-catalyzed (mainly, Fe, Ni, Cu) transformations of
oxime esters have been reported recently in which the activation processes
are assumed to follow free-radical mechanisms. In this work, we show
by means of density functional theory calculations that the activation
of oxime esters catalyzed by Fe(II) and Cu(I) catalysts more likely
affords a metal-bound iminyl radical, rather than the presumed free
iminyl radical, and the whole process follows a metal-bound radical
mechanism. The as-formed metal-bound radical intermediates are an
Fe(III)-iminyl radical (Stotal = 2, SFe = 5/2, and Siminyl = −1/2) and a Cu(II)-iminyl radical (Stotal = 0, SCu = 1/2, and Siminyl = −1/2). The discovery of such
novel substrates affording metal-bound radical intermediates may facilitate
the experimental design of metal-catalyzed asymmetric synthesis using
oxime esters to achieve the desired enantioselectivity