Iodination of dibenzoylmethanes with iodine–peracetic acid

Abstract

The reaction of dibenzoylmethane (enol content ca. 97%) with iodine–peracetic acid gave dibenzoyliodomethane (keto form) in >90% yield. However, no di-iodo-derivative was obtained by using an excess of reagent. Some p-substituted dibenzoylmethanes were also iodinated by this method in fairly high yields. However, 1,1-dibenzoylethane (keto form) was stable to the reagent. This high reactivity of enols together with some kinetic results suggest that the mechanism may be similar to that of the iodoacetoxylation of propene. Dibenzoyliodomethane was also obtained in good yield by the reaction of dibenzoylmethane with iodine–iodic acid, which also gave a di-iodo-derivative in high yield when used in excess.