A key iodine(III) enolate intermediate forms, which then undergoes either nucleophilic substitution (α-functionalization), elimination (dehydrogenation), or rearrangement.
[1] The mechanism of carbonyl oxidation by iodine(III) reagents varies as a function of substrate structure and reaction conditions, but some generalizations are possible.
Under acidic conditions, oxidations of aryl enol ethers lead to α-aryl esters via 1,2-aryl migration.
Iodine approaches on the side opposite the chromium tricarbonyl unit due to steric hindrance.
Bulky diaryliodoniums react more slowly, and enolate homocoupling (see equation (10) below) begins to compete as the aromatic ring is substituted.
[1] Silyl enol ethers undergo many of the same reactions as carbonyl compounds in the presence of iodine(III) reagents.
Aryl migration may occur under acidic conditions, yielding α-aryl esters from enol ethers.
[1] Oxidative functionalization of silyl enol ethers in low concentration (to avoid homocoupling) without an external nucleophile leads to dehydrogenation.
The Willgerodt-Kindler reaction of alkyl aryl ketones, for instance, requires forcing conditions and often gives low yields of amide products.