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.