Radical cations. Part 3. Chemical and electrochemical oxidation of 3,3′-bis-indolizines

Abstract

Indolizine dimers 1a–c are oxidized by chemical and electrochemical methods. Anodic oxidation shows that the title compounds are oxidized in two different steps, and cyclic voltammetry demonstrated their reversibility. The radical cations 2a–c and the dications 3a–c are characterized by an EPR study and by comproportionation reactions, respectively. The dimmers 1a–c, treated with diazonium ions, undergo retrogression reactions, forming the arylazoindolizines 7a and 7b. Formation of the radical cation 2b in the reaction of compound 1b with diazonium salts has been explained through the homolytic evolution of the intermediate σ-complex by means of an indolic aminoxyl as radical scavenger.