The reaction of Ni(II) acetate with
diacyl peroxides produces high-valence
Ni-species capable of catalytic oxidative acyloxylation of C(sp3)–H bonds in ethers, ketones, and alkanes. The desired
esters were obtained in 20–82% yields. Computational analysis
suggests that activation of the peroxide moiety produces a dynamically
interconverting mixture of catalytic Ni-species in the formal Ni(III)
state. Remarkably, in these species, coordination of the RCO2 group at Ni preserves radical character at the carboxylate moiety
(i.e., carboxylate radical acts as an “L-ligand”), so
the latter can induce fast C–H abstraction. The spirocyclopropyl
moiety prevents premature radical decarboxylation via a combination
of hybridization factors and stereoelectronic effects. A variety of
viable C–H activation patterns were identified experimentally
and computationally.