Enthalpic and polar effects in the reactions of perfluoroalkyl radicals - New selective synthetic developments with alkenes and heteroaromatic bases

Perfluoroalkyl radicals, generated by iodine abstraction from perfluoroalkyl iodides by phenyl radical, react with low selectivity with protonated heteroaromatic bases, due to their electrophilic character and the prevalent enthalpic effect on the reaction. In the presence of alkenes, perfluoroalkyl radicals add very rapidly to the double bond and the polar character of the radical adduct is reversed, allowing the selective substitution of protonated heteroaromatic bases. The mechanism of the reaction and the key role of enthalpic and polar effects are discussed. (C) 2003 Elsevier B.V. All rights reserved.