On the Phenyliodine(III)-bis(trifluoroacetate)-mediated olefin amidohydroxylation reaction

When appropriately substituted amides are treated with PIFA in a non-nucleophilic solvent like trifluoroethanol, a stable N-acylnitrenium ion is generated. If under such conditions a C=C double bond is present in the molecule, an intramolecular cyclization process takes place in an exo mode with additional generation of a hydroxy group at the terminal position of the original olefin moiety to render a series of pyrrolidine and piperidine derivatives. In this paper, proofs are offered to conclude that, according to our assumption, an ionic mechanism rather than a radical one must be considered. Additionally, a study of the scope of this cyclization protocol is conducted using substrates with different substituents either on the amidic nitrogen or all along the carbon chain. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007).