Protecting stereoelectronic effects prevent Baeyer–Villiger rearrangement and stabilize γ-OX-γ-peroxylactones (X = H, OH), the previously elusive non-strained Criegee intermediates.

We show that the carboxylate radical acts as an L-ligand with certain high-spin transition metal centers. Such coordination preserves the O-radical character needed for C−H activation via hydrogen atom transfer. Capture of the new C-radical by the metal and subsequent reductive elimination leads to formal C−H acyloxylation. Decarboxylation of the RCO 2 radical is minimized through hybridization effects introduced by spiro-cyclopropyl moiety.

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Stereoelectronic interactions control reactivity of peroxycarbenium cations, the key intermediates in (per)oxidation chemistry.C omputational analysis suggests that alcohol involvement as at hird component in the carbonyl/peroxide reactions remained invisible due to the absence of sufficiently deep kinetic traps neededt op reventt he escapeo f mixed alcohol/peroxidep roducts to the more stable bisperoxides.S ynthesis of b-alkoxy-b-peroxylactones, an ew type of organic peroxides, was accomplished by interrupting a thermodynamically driven peroxidation cascade. The higher energy b-alkoxy-b-peroxylactones do not transform into the more stable bisperoxides due to the stereoelectronically imposedi nstability of ac yclic peroxycarbenium intermediate as aconsequence of amplified inversea lpha-effect. The practical consequence of this fundamentalf inding is the first three-component cyclization/condensation of b-ketoesters, H 2 O 2 ,a nd alcohols that provides b-alkoxy-b-peroxylactones in 15-80 %yields.[a] Dr.