Bismuth supported on phosphonium functionalized chitosan as sustainable heterogeneous catalysts for one-pot Biginelli condensation

An easy synthesis of a novel solid catalyst based on chitosan grafted with phosphonium ionic liquid (CS@PIL) supporting bismuth (Bi) was carried out through a two-step process. In the first step, chitosan was modified with phosphonium ionic liquid (PIL), and in the second step, Bi(III) ions were coordinated to the chelating groups on the solid support. The resulting materials were characterized using various techniques, including FTIR and solid-state NMR spectroscopy, scanning electron microscopy (SEM), X-ray diffraction, ICP-MS, and thermogravimetry. It was found that the desired products of Biginelli condensation couldn't be obtained when Bi(III) was supported on native chitosan due to the reactivity of its NH2 groups with the aldehyde reactant In turn, the modified CS@PIL@Bi catalyst exhibited remarkable efficiency and recyclability as a heterogeneous catalyst in the one-step Pietro Biginelli condensation reaction.