ANODIC CHLORINATION OF SUBSTITUTED BENZENES - CHOICE OF THE CHLORINATION REAGENTS

Some substituted benzenes ArH were anodically chlorinated in acetonitrile LiClO4 on a platinum electrode in the presence of either Cl- anion or a chlorinated Lewis acid (such as AlCl3). The overvoltage on the oxidation of Cl- caused by a strong complexation by some Lewis acid allows consideration that the anodic reaction passes through the radical cation of the aromatic substrate. In such conditions, polychlorinations are possible and in the specific case of toluene, it is shown that the reaction favors the parachlorotoluene formation. The influence of different parameters (for example, the ratio of the concentrations AlCl3/ArH, the nature of the Lewis acid) in such a reaction are discussed. © 1979.