Perlite: A cheap natural support for immobilization of sulfonic acid as a heterogeneous solid acid catalyst for the heterocyclic multicomponent reaction

Abstract

Perlite sulfonic acid (Perlite-SO3H (PeSA)) has been synthesized by grafting the sulfonic groups on the perlite surface as naturally and cheap support to produce novel heterogeneous reusable solid acid catalysts. FT-IR, XRD, SEM, TGA, pH analysis and Hammett acidity function were employed to characterize the properties of the synthesized PeSA. Significantly, the as-prepared PeSA exhibits a high catalytic activity in multicomponent reaction for the one-pot synthesis of heterocyclic compound such as 3,4-dihydropyrimidin-2(1H)-ones, 2,4,5-trisubstituted imidazoles, coumarins and bis(indolyl)methanes. Additionally, the newly synthesized heterogeneous solid acid catalyst can be reused for several times without apparent loss of its catalytic activity, confirming the stability of the covalent bonding of acidic centers. PeSA has advantages such as low cost, ease of preparation, more stability and reusability, low toxicity and ease of handling.