Iodoarene-mediated one-pot preparation of 2,5-disubstituted and 2,4,5-trisubstituted oxazoles from alkyl aryl ketones with oxone in nitriles

The reaction of alkyl aryl ketones with Oxone® and trifluoromethanesulfonic acid in the presence of iodoarene in acetonitrile, propionitrile, butyronitrile, and isobutyronitrile, provided directly the corresponding 2,5-disubstituted and 2,4,5-trisubstituted oxazoles, respectively, in moderate yields. Here, reactive aryliodonium I(III) species is formed in situ by the reaction of iodoarene with Oxone® and trifluoromethanesulfonic acid, and the formed aryliodonium I(III) species reacts with alkyl aryl ketone to generate β-keto iodonium species. Then, β-keto iodonium species reacts with nitrile to produce the corresponding oxazole. In principle, iodoarene works as a catalyst. However, 1 equiv of iodoarene is required because 1 equiv of reactive aryliodonium I(III) species must be formed before the reaction with alkyl aryl ketone.