A convenient procedure for the preparation of α-iodo
ketones by oxidative iodination of ketones using iodine and m-iodosylbenzoic acid as a recyclable
hypervalent iodine oxidant is reported. Various ketones and β-dicarbonyl
compounds can be iodinated by this reagent system under mild conditions
affording the respective α-iodo-substituted carbonyl compounds
in excellent yields. The final products of iodination are conveniently
separated from byproducts by simple treatment with anionic exchange
resin Amberlite IRA 900 HCO3
- and
are isolated with good purity after evaporation of the solvent.
The reduced form of the hypervalent iodine oxidant, m-iodobenzoic acid, can be recovered
in 91-95% yield from the Amberlite resin by treatment
with aqueous hydrochloric acid followed by extraction with ethyl
acetate.
halogenation - iodine - ketones - iodosylbenzene -
m-iodosylbenzoic acid - hypervalent
iodine