Dual thiophilic or carbophilic reactivity of N, N-dialkyl perfluorocarboxylic thioamides with organometallic reagents

Abstract

N, N-dialkyl amides of perfluorothiocarboxylic acids react with organomagnesium and organolithium reagents via thiophilic or carbophilic attack of carbanion on the C S bond. The chemoselectivity depends on the nature of the organometallic species. Lithium reagents react at sulfur, with a subsequent β-elimination of fluoride, giving an N, S-ketene acetal. Simple organomagnesium reagents do not react, whereas allylmagnesium halide reacts at carbon, giving an adduct which can be trapped by methyl iodide and converted to the corresponding N, S-acetal. The latter can be transformed into a perfluoroalkyl dienamine via oxidation.