N-Perfluoroalkylsulfonylimido derivatives of arenecarboxylic acid amides and their oxidative aza Hofmann rearrangement

The analogues of carboxamides in which the sp2-hybridized oxygen atom is replaced by more electron-withdrawing groups, NSO2CF3 and NSO2C4F9, have been synthesized. The resulting N-perfluoroalkylsulfonyl arenecarboxamidines ArC(NSO2Rf)NH2 (Rf = CF3, C4F9) undergo an oxidative Hofmann-type rearrangement to the corresponding carbodiimides ArNCNSO2Rf under the action of (diacyloxyiodo)arenes. Rearrangement of related compounds ArC(NSO2R)NH2 (R = CH3, Ph) containing fluorine-free substituents at the sulfonyl group also occurs in similar conditions. It was found that the reactivity of amidines rises with the increasing electron-withdrawing ability of the substituent R.