A hypervalent iodine reagent-based alpha-carbonyl dihalogenation reaction is reported. Treating diazoacetate derivatives with either iodobenzene dichloride or iodotoluene difluoride results in gem-dichlorination or gem-difluorination products, respectively. The reaction is catalyzed by either Lewis acid or Lewis base activation of the aryl-lambda(3)-iodane (ArIX2) species and proceeds rapidly and chemoselectively to the desired gem-difunctionalized products in good to excellent yield.