Covalently anchored sulfamic acid on cellulose as heterogeneous solid acid catalyst for the synthesis of structurally symmetrical and unsymmetrical 1,4-dihydropyridine derivatives

Abstract

A novel heterogeneous solid acid catalyst has been prepared by covalent grafting of chlorosulphonic acid on amino-functionalized cellulose (Cell–Pr-NHSO₃H). The structure of the catalyst was assessed by FT-IR, solid-state CP/MAS ¹³C-NMR spectroscopy, field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX), thermogravimetric (TGA) and CHNS analysis. The catalytic performance of the heterogeneous acid catalyst is evaluated in the synthesis of structurally symmetrical and unsymmetrical 1,4-dihydropyridines (1,4-DHPs). High conversion, shorter reaction time, cleaner reaction profile, environmentally benign solvent, simple experimental and work-up procedure, and reusability of the catalyst are the striking features of our synthetic route.