An efficient approach to 2-CF3-indoles based on ortho-nitrobenzaldehydes

Abstract

The catalytic olefination reaction of 2-nitrobenzaldehydes with CF3 CCl3 afforded stereose-lectively trifluoromethylated ortho-nitrostyrenes in up to 88% yield. The reaction of these alkenes with pyrrolidine permits preparation of α-CF3-β-(2-nitroaryl) enamines. Subsequent one pot reduction of nitro-group by Fe-AcOH-H2 O system initiated intramolecular cyclization to afford 2-CF3-indoles. Target products can be prepared in up to 85% yields. Broad synthetic scope of the reaction was shown as well as some followed up transformations of 2-CF3-indole.