Peroxycarbenium Ions as the Gatekeepers in Reaction Design: Assistance from Inverse Alpha-Effect in Three-Component β-Alkoxy-β-peroxylactones Synthesis

Stereoelectronic interactions control reactivity of peroxycarbenium cations, the key intermediates in (per)oxidation chemistry. Computational analysis suggests that alcohol involvement as a third component in the carbonyl/peroxide reactions remained invisible due to the absence of sufficiently deep kinetic traps needed to prevent the escape of mixed alcohol/peroxide products to the more stable bisperoxides. Synthesis of beta-alkoxy-beta-peroxylactones, a new type of organic peroxides, was accomplished by interrupting a thermodynamically driven peroxidation cascade. The higher energy beta-alkoxy-beta-peroxylactones do not transform into the more stable bisperoxides due to the stereoelectronically imposed instability of a cyclic peroxycarbenium intermediate as a consequence of amplified inverse alpha-effect. The practical consequence of this fundamental finding is the first three-component cyclization/condensation of beta-ketoesters, H2O2, and alcohols that provides beta-alkoxy-beta-peroxylactones in 15-80 % yields.