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

N,N-dialkyl amides of perfluorothiocarboxylic acids react with organomagnesium and organolithium reagents via thiophilic or carbophilic attack of carbanion on the CS 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.