Iodobenzene-Catalyzed α-Acetoxylation of Ketones. In Situ Generation of Hypervalent (Diacyloxyiodo)benzenes Using <i>m</i>-Chloroperbenzoic Acid

Reported here for the first time is the iodobenzene-catalyzed α-oxidation of ketones, in which diacyloxy(phenyl)-λ3-iodanes generated in situ act as real oxidants of ketones and m-chloroperbenzoic acid serves as a terminal oxidant. Oxidation of a ketone with m-chloroperbenzoic acid in acetic acid in the presence of a catalytic amount of iodobenzene, BF3·Et2O, and water at room temperature under argon affords an α-acetoxy ketone in good yield. p-Methyl- and p-chloroiodobenzene also serve as efficient catalysts in this direct oxidation. We found that when the reaction was carried out in the absence of a catalytic amount of iodobenzene, Baeyer−Villiger oxidation of a ketone took place. It is noted that use of water and BF3·Et2O is crucial to the success of this α-acetoxylation.