Electrochemical oxidation of aryl cycloheptatrienes

The electrochemical oxidation of various substituted aryl cycloheptatrienes and cyclohepta-1,3,5-triene, the parent compound, in acetonitrile is inves tigated with the aid of cyclic voltammetry (CV), experiments at the rotatin g ring disk electrode (RRDE) and controlled potential electrolysis. 1-(p-me thoxyphenyl)-cycloheptatriene 2c, 1- and 3-(p-dimethylaminophenyl)-cyclohep tatriene 2d, 3d are converted by anodic oxidation into the radical cations the main reaction of which is not the deprotonation. According to the propo sed mechanism the electrochemical oxidation proceeds along the radical cati on dimerization. The dimer cations (1(2)(2+)) decompose under deprotonation into tropylium ions 4 and starting compound. In the case of 1-(p-dimethyla minophenyl)-cycloheptatriene 2D the deprotonation reaction can compete with the dimerization. The oxidation of the cycloheptatriene compounds is kinet ically controlled by the homogeneous chemical steps rather than by the init ial electron transfer.