Synthesis of pyrrolo[1,2-a]naphthyridines by Lewis acid mediated cycloisomerization.

Abstract

Pyrrolo[1,2-a]naphthyridines were synthesized from 3-alkynyl-2-([1H]-pyrrol-1-yl)pyridines and 3-alkynyl-4-([1H]-pyrrol-1-yl)pyridines by cycloisomerization. The reactions are performed by application of the Lewis acids PtCl2 or Bi(OTf)3 without the need of further additives. With the described methods a number of derivatives containing a variety of functional groups have been synthesized in up to 78% yield.