Polystyrene-supported p-toluenesulfonic acid (PS/PTSA): as a highly active and reusable heterogeneous bronsted acid catalyst for the synthesis of novel 1H-indol-3-yl-4H-chromene-3-carbonitriles under neat conditions

Abstract

An efficient and environmentally benign protocol for the synthesis of a new class of diversely functionalized novel 1H-indol-3-yl-4H-chromene-3-carbonitriles has been described through one-pot three-component condensation reaction of 3-(1H-indol-3-yl)-3-oxopropanenitrile, 5,5-dimethylcyclohexane-1,3-dione, and various aldehydes in the presence of polystyrene-supported p-toluenesulfonic acid (PS/PTSA) under solvent-free conditions. The present methodology offers several advantages such as short reaction time, simple operational procedure, avoid toxic solvent, high yield of product and endures the substrate diversity. The PS/PTSA catalyst is readily available in stable form which is fairly inexpensive and can be easily recovered from the reaction medium without appreciable changes for further reuse in the consecutive reaction cycles effectively.