Radical addition of ketones to alkenescatalyzed by Mn(OAc)2 combined with Co(OAc)2 using dioxygen as oxidant was developed; for instance, the reaction of cyclohexanone with oct-1-ene in the presence of very small amounts of Mn(OAc)2 and Co(OAc)2 under air (1 atm) gave 2-octylcyclohexanone in good selectivity; from styrene, a six-membered cyclic peroxide was isolated in good yield.