An electrochemical aromatic chlorination, comparison with electrophilic reaction

The electrophilic and the anodic chlorination of 1,4-dimethoxy-2-tert-butylbenzene appear to involve different mechanistic pathways. The electrophilic chlorination of 1,4-dimethoxy-2-tert-butylbenzene requires Lewis acid catalysts when carried out in CCl4 but not in CH3CN. It yields 1,4-dimethoxy-2-tert-butyl-5-chlorobenzene as the primary product and in subsequent reactions 1,4-dimethoxy-2,5-dichlorobenzene, 1,4-dimethoxy-2-tert-butyl-dichlorobenzene and 1,4-dimethoxy-2-chlorobenzene. In contrast, anodic chlorination of 1,4-dimethoxy-2-tert-butylbenzene in CH3CN yields 1,4-dimethoxy-2-tert-butyl-6-chlorobenzene and 1,4-dimethoxy-2-tert-butyl-5-chlorobenzene in about equal amounts. Further chlorination is forestalled and replacement of the tert-butyl group is not observed. 1,4-Dimethoxy-2-tert-butyl-6-chlorobenzene is therefore the main product of the electrochemical route.