A short route to heteroarylcarbazoles: Synthesis of new pyrazolylcarbazoles and carbazolylquinolines

Abstract

A short synthesis of pyrazolylcarbazoles from 9-alkyl-carbazoles in three steps is reported. The acetylcarbazoles prepared by the acetylation of carbazoles with acetic anhydride catalyzed by BiCl3 were converted into chloroaldehydes with Vilsmeier reagent. Condensation of chloroaldehydes with hydrazine followed by cyclization yield the pyrazolylcarbazoles. Carbazolyl chalcones were prepared by the condensation of carbazole-3-aldehyde with o-aminoacetophenone and cyclized to carbazolylquinolone using several catalysts. Cyclization of carbazolyl chalcones with the Vilsmeier reagent yields a mixture of carbazolylquinoline carbaldehydes.