Perfluoroalkylations of nitrogen-containing heteroaromatic compounds with bis(perfluoroalkanoyl) peroxides

Abstract

Perfluoroalkylations of nitrogen-containing heteroaromatic compounds with bis(perfluoroalkanoyl) peroxides were studied. Bis(trifluoroacetyl) peroxide, bis(heptafluorobutyryl) peroxide, and bis(pentadecafluoro-octanoyl) peroxide were found to be useful and effective reagents for perfluoromethylations, perfluoropropylations, or perfluoroheptylations of pyrrole and its derivatives, while these peroxides could not be applied for the perfluoroalkylations of pyridine or imidazole. For the perfluoroalkylations with the peroxides, electron transfer from the substrate to the peroxide, which affords a perfluoroalkyl radical and a cation radical of the substrate in a solvent cage, is proposed. In pyrroles, since the delocalization of the N lone pair to π-systems lowers the nucleophilicity of the N lone pair and increases the electron density at the π-orbital, the electron transfer readily occurred and perfluoroalkylated pyrroles were obtained in good yield and regioselectively. However, nucleophilic attack of the N lone pair to the O–O bond of the peroxide was superior to the electron transfer in pyridine or imidazole of which the N lone pairs are very nucleophilic.