Reaction of CuI with Dialkyl Peroxides: CuII-Alkoxides, Alkoxy Radicals, and Catalytic C-H Etherification

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