Anodic Halogenation of Aromatics

The electrochemical nuclear chlorination of substituted aromatics in some cases allows to achieve better regioselectivities than the chemical alternatives. DOW 93 94) has shown that, in the anodic chlorination of toluene in aprotic electrolytes, the p/o ratio of the chlorotoluenes can be increased to about 2.2 (chemical alternatives 0.5-1, depending on substances added to the reaction mixture)  

The use of graphite anodes modified with cyclodextrins allows to increase the pjo ratio to above 4 and at the same time to use aqueous electrolytes (NaCl, HC1—H20) 95-96) Electrochemical halogenation has been used in particular by Japanese companies for the synthesis of intermediates on the laboratory scale. A few examples are given below  

DuPont102) has used the anodic iodination of aniline as the key step in the formation of p-phenylenediamine. 

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