One pot aza-Friedel-Crafts multicomponent reaction under green chemistry conditions

Abstract

Indole and its 3-substituted derivatives play crucial roles in various biological life forms and whilst some of them are naturally-occurring, others have been synthesized for their pharmaceutical capabilities. This study entailed synthesizing 3-substituted indoles via the one-pot multicomponent aza-Friedel-Crafts reactions, starting from a very wide range of aldehydes; primary, secondary and tertiary aromatic amines; and indoles. Following the principles of green chemistry, catalyst screening and condition optimization were performed on a model reaction. It was found that the reactions could be catalyzed by a heterogeneous, recyclable, easily and safely-prepared catalyst: silicotungstic acid supported on Amberlyst 15 beads.