Effect of chloride ions on the indirect electrosynthesis of 2,6-dichlorobenzonitrile mediated by iodide

Abstract

• Synthesis of 2,6-dichlorobenzonitrile by indirect electrochemical method. • The presence of chloride ion facilitates the reaction. • Cyclic voltammetry revealed the effect of chloride ion on I − oxidation. • Cl − promoted further oxidation of I 2 to I + . An efficient and mild iodide-mediated indirect electrooxidation method to prepare 2,6-dichlorobenzonitrile was developed. Cyclic voltammetry and potentiostatic electrolysis were carried out to investigate the feasibility of this approach for 2,6-dichlorobenzaldehyde. Unexpectedly, an increase in the synthetic efficiency was obtained when the solution contained chloride ions. The cyclic voltammetric results indicated that an interhalide species, namely [ICl 2 ] − , was formed during oxidation of the iodide ion in the solutions containing chloride ions; this result was in contrast to the expected formation of the less electrophilic I 2 . The strong electrophilicity of [ICl 2 ] − greatly enhanced the efficiency of the electrosynthetic approach to 2,6-dichlorobenzonitrile. Overall, this synthesis system provides a green and efficient route to 2,6-dichlorobenzonitrile, and hence, could be potentially applicable in the industrial preparation of aromatic nitriles.