Novel convenient 2-step synthesis of pyrido[1,2- a ]indoles from pyrylium salts and o -bromoanilines.

A novel convenient 2-step synthesis of substituted pyrido[1,2- a ]indoles is developed starting from easily available pyrylium tetrafluoroborates and ortho -bromoanilines. A conversion of the pyrylium tetrafluoroborates to pyridinium ones followed by their palladium catalyzed intramolecular cyclization allows the formation of 24 examples of N-fused heterocycles. A one-pot two-stage cyclization procedure was developed. The utility of the methodology was demonstrated with the synthesis of new pyrido[1,2- a ]indoles bearing different alkyl, aryl, chlorine, fluorine and methoxy substituents.