Nucleophilic Substitution of an Anodically Generated Radical Cation

Nuclear and side chain substitution in aromatics or substitution of a -hydrogen in alkylamines is — in most cases — best rationalized by postulating radical cations as intermediates. For anodic nuclear substitution of aromatics, especially for acyloxylation, cyanation or bromination a ECnECb3 -mechanism is assumed 37,4 9,50,226,227). jc-oxidation of the aromatic to the radical cation 28, which reacts with a nucleophile Nu, e.g., acetate, cyanide, alkoxide, followed by a second electron transfer and deprotonation (Eq. (98) )  

Cumene, toluene, ethylbenzene (CH3CN, Et3N, benzoic acid 

Anisole, toluene, ethyl- O- and p-Nitrilcs (low current yields benzene (NaCN, MeOH) 1-12%) 

Toluene, mesitylene Exclusive nuclear cyanation, selective in 57) 

Phenol has been hydroxylated nearly quantitatively to hydroquinone 2 3 9 Most alkoxylations or hydroxylations of aromatics however either lead to anodic addition products (see Sect. 10.1) or to side chain substitution (see below). Specific side-chain hydroxylation is difficult to achieve because the alcohols formed as primary products are further oxidized to aldehydes, ketones and/or carboxylic acids. 

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Nucleophilic substitution of an anodically generated radical cation (Eq. (91)) ... 

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