Organic dye-photocatalyzed fluoroalkylation of heteroarene-N-oxide derivatives

Abstract

The first direct C_Het–H perfluoroalkylation reaction of heteroaromatic-N-oxides has been achieved through a visible light-photocatalyzed reaction in the presence of commercially available perfluoroalkyl iodides R_F–I and base in DMF as solvent and Rose Bengal as organic photocatalyst. The reactions proceed in the absence of transition metals and can be scaled up. Through an acid-catalyzed transformation of the perfluoroalkylated-N-oxides thus obtained, the first direct syntheses of 2-(perfluoroalkyl)benzo[f][1,3]oxazepines are achieved. De-oxygenation of the resulting perfluoroalkylated heteroaromatic-N-oxides leads to high yielding and regioselective radical perfluoroalkylation protocols of heteroaromatic compounds. To the best of our knowledge, this is the first report on a direct method for perfluoroalkylation of pyridine-, quinoline-, and diazine-N-oxide derivatives.