text: Manganese(III)-mediated radical reactions begin with the single-electron oxidation of a carbonyl compound to an α-oxoalkyl radical. Addition to an olefin then occurs, generating adduct radical 2. The fate of 2 is primarily determined by reaction conditions—in the presence of copper(II) acetate, this intermediate undergoes further oxidation to a carbocation and may eliminate to form β,γ-unsaturated ketone 4. Manganese acetate itself can effect the second oxidation of resonance-stabilized adduct radicals to carbocations 5; unstabilized radicals undergo further transformations before reacting with Mn(OAc). Atom transfer from another molecule of substrate may generate saturated compound 3. Adduct radicals or carbocations may undergo ligand-transfer reactions, yielding γ-functionalized carbonyl compounds. When lithium chloride is used as an additive, chlorination takes place. Alternatively, carbocations may be trapped intramolecularly by the carbonyl oxygen to form dihydrofurans after β-elimination.