Polyionic liquid decorated chitosan beads as versatile metal-free catalysts for catalyzing chemical reactions in aqueous media

Abstract

A new strategy is presented for enhancing the catalytic activity of cross-linked chitosan beads. More precisely, chitosan beads were cross linked with glutaraldehyde and then, vinyl functionalized. In the next step, the vinyl-functionalized beads were polymerized with the as-prepared 1-vinyl-3-butylimidazolium bromide to furnish polyionic liquid on beads. The resultant composite was subsequently utilized as a metal-free catalyst for catalyzing some classic organic transformations, including Knoevenagel condensation reaction and syntheses of tetrahydrobenzo[b]pyrans and pyrano[2,3-d]pyrimidines in aqueous media under mild reaction conditions. It was found that the novel composite could efficiently promote all of the examined reactions to afford the corresponding products in high yields. Moreover, the catalyst exhibited high recyclability for all reactions. The comparative studies also approved that the activity of the composite was superior compared to cross-linked bead and polyionic liquid.