Electronic, steric and acid-base effects on the anodic oxidation of aryl-substituted ketene imines

Aryl-substituted ketene imines (1a-1i) have been studied both in dichloromethane and acetonitrile by cyclic voltammetry. In addition to the multi-annulated heterocycles products of type 2-4 previously obtained by ketene imines 1a-1d, the anodic oxidation of ketene imines containing electron-withdrawing substituents and electron-donating substituents at the ortho position, affords also monocyclic dimers of type 5 (from 1e-1f) and of type 6 (from 1h-1i). The results are discussed in terms of both electronic and steric effects.