Magnetic lignin-supported sulfonic acid ionic liquid: a novel catalyst for synthesis of 2-amino-4-aryl-4H-benzo[f]chromen-3-carbonitrile derivatives

Abstract

A novel Brønsted acidic ionic liquid immobilized on modified magnetic lignin (Fe₃O₄/MPL–[IL]) was successfully synthesized and comprehensively characterized by FT-IR, XRD, EDX, VSM, FE-SEM, TGA, and TEM analyses. The prepared nanocatalyst was utilized for preparing 2-amino-4-aryl-4H-benzo[f]chromene-3-carbonitriles via the reaction between aryl aldehydes, β-naphthol, and active methylene compounds (malononitrile or ethyl cyanoacetate), affording high yields of 87–97% within short reaction times (20–80 min) under mild conditions. Necessary experiments were conducted for the recyclability test of the prepared catalyst, and the results showed that the Fe₃O₄/MPL–[IL] nanocatalyst can be reused five times while maintaining about 95% of its initial catalytic activity, with excellent stability.