Reaction of Cu^I with Dialkyl Peroxides: Cu^II-Alkoxides, Alkoxy Radicals, and Catalytic C–H Etherification

Kinetic analysis of the reaction of the copper­(I) β-diketiminate [Cl₂NN]Cu ([Cu^I]) with ^tBuOO^tBu to give [Cu^II]–O^tBu (1) reveals first-order behavior in each component implicating the formation of free ^tBuO^• radicals. Added pyridine mildly inhibits this reaction indicating competition between ^tBuOO^tBu and py for coordination at [Cu^I] prior to peroxide activation. Reaction of [Cu^I] with dicumyl peroxide leads to [Cu^II]–OCMe₂Ph (3) and acetophenone suggesting the intermediacy of the PhMe₂CO^• radical. Computational methods provide insight into the activation of ^tBuOO^tBu at [Cu^I]. The novel peroxide adduct [Cu^I]­(^tBuOO^tBu) (4) and the square planar [Cu^III]­(O^tBu)₂ (5) were identified, each unstable toward loss of the ^tBuO^• radical. Facile generation of the ^tBuO^• radical is harnessed in the catalytic C–H etherification of cyclohexane with ^tBuOO^tBu at rt employing [Cu^I] (5 mol %) to give the ether Cy–O^tBu in 60% yield.