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 (R) 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 (R) and trifluoromethanesulfonic acid, and the formed aryliodonium I(III) species reacts with alkyl aryl ketone to generate beta-keto iodonium species. Then, beta-keto iodonium species reacts with nitrile to produce the corresponding oxazole. In principle, iodoarene works as a catalyst. However, I equiv of iodoarene is required because I equiv of reactive aryliodonium I(III) species must be formed before the reaction with alkyl aryl ketone. (C) 2009 Elsevier Ltd. All rights reserved.