Iodination of Methylated Anisoles: Unusual Aryl Methyl Replacement and Oxidations

Article abstract of DOI:10.1021/jo00129a041

The treatment of methylated anisoles with iodine, periodic acid, sulfuric acid, and aqueous acetic acid has resulted in iododemethylations and/or aryl methyl oxidations in addition to the expected mono- and diiodinations of the aromatic ring.Four dimethylanisoles and o-methylanisole were treated under identical conditions.Iododemethylations were observed in three of the four dimethylanisoles and aryl methyl oxidations to benzaldehydes occured with o-methylanisole and two of the dimethylanisoles.No precedence could be found for either of these reactions under the experimental conditions employed.Several possible mechanisms are discussed for these transformations.Some experimental evidence suggests that methyl oxidation to a benzaldehyde could be a prerequisite for an iododemethylation via an iodonium ion-assisted reverse Gatterman-Koch reaction; single-electron-transfer or classical electrophilic mechanisms are also consistent with the iododemethylations.