Carbon‐Carbon Bond Cleavage of the [2.2]Paracyclophane Radical Cation Generated by Electron Transfer Oxidation with Cerium(IV) Ammonium Nitrate

Abstract

AbstractSingle electron transfer (SET) oxidation of [2.2]paracyclophane (1) with cerium ammonium nitrate (CAN) produces the corresponding radical cation (1+.), which undergoes cleavage of the carbon‐carbon bond of the ethano bridge to generate the double‐benzylic radical cation 2+. Trapping of this intermediate by oxygen and nucleophiles gives rise to aldehydes 3, while a second oxidation and subsequent nucleophilic trapping affords nitrates 4. This facile cleavage of the carbon‐carbon bond is explained by alignment of the latter with the π systems in the rigid structure of [2.2]paracyclophane, which enables charge delocalization across both benzene rings. When the reaction is carried out in methanol, aromatic substitution takes also place as a minor reaction pathway, which is responsible for the formation of the polyfunctionalized cyclophane 5d.