Hypervalent iodine(III)-mediated oxidation of aldoximes to N-acetoxy or N-hydroxy amides

Treatment of various aliphatic and aromatic aldoximes with the hypervalent iodine(III) reagents (diacetoxyiodo)benzene (DIB) or Koser's reagent [hydroxy(tosyloxy)iodo]benzene (HTIB) gave, respectively, N-acetoxy or N-hydroxy amides in good yields rather than the expected nitrile oxide dimerised product oxadiazole-N-oxides reported to be formed with other oxidising and hypervalent iodine reagents. The acetate or the hydroxyl group of DIB or HTIB attacks on the aryl/alkylnitrile oxides formed in situ, which, upon intramolecular rearrangement, gave the expected N-acetoxy or N-hydroxy amides.