Synthesis of novel ferrocenyl-containing pyrazolo[4,3-c]quinolines

Synthesis of novel ferrocenyl-substituted pyrazolo[4,3-c]quinolines via the Pictet–Spengler reaction is reported. Iminium intermediate formed by the condensation of pyrazole-based arylamine substrates with ferrocenecarboxaldehyde in acidic medium, undergoes 6-endo cyclization with sufficiently reactive aromatic moiety to form a pyrazolo[4,3-c]quinoline ring.

Graphical abstractNovel mono and diferrocenyl substituted pyrazolo[4,3-c]quinolines derivatives have been synthesized and characterized by FT-IR, 1H-NMR, 13C-NMR spectroscopy and/or elemental analysis. These ferrocenyl-substituted pyrazolo[4,3-c]quinolines were prepared by the Pictet–Spengler reaction between arylamine substrates linked to pyrazole ring and ferrocenecarboxaldehyde in acidic medium.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Novel mono and diferrocenyl substituted pyrazolo[4,3-c]quinolines have been prepared by modified Pictet-Spengler reaction in moderate yields. ► The Pictet-Spengler reaction was performed by the reaction of pyrazole-based aryl amine substurate with ferrocenecarboxaldehyde in acidic medium. ► FT-IR, NMR characterization and elemental analysis of the resulting compounds have been performed. ► Mono ferrocenyl imine derivatives have better electrophilicity than diferrocenyl imine ones, therefore they are more reactive in order to go Pictet-Spengler reaction.