SO3H@carbon powder derived from waste orange peel: An efficient, nano-sized greener catalyst for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives

Abstract

Carbon nano/micro powder provides an innovative approach in the field of green catalysis by enhancing its efficiency and reusability for several chemical transformations. In this present work, we have developed an improved, forthright, highly efficient waste orange peel derived carbon (OPC) powder incorporated with sulfonic acid (OPC-SO3H) as a greener, highly efficient and reusable catalyst for the facile synthesis of dihydropyrano[2,3-c]pyrazole derivatives via one pot four component strategy. The prepared OPC-SO3H powder was characterized by FT-IR, XRD, SEM, EDX, DLS-particle size, Zeta potential, TGA-DTA, BET and XPS binding studies, all the analytical techniques revealed the structural properties of prepared OPC-SO3H carbon powder. Especially, DLS analysis showed the OPC-SO3H particle size between 300 to 400 nm. A Zeta potential of −21.1 mV indicated its moderate stability and TGA/DTA studies exemplifies the thermal decomposition pattern of OPC-SO3H. BET studies indicate the surface textural properties of OPC & OPC-SO3H and the decrease in specific surface area, porous structure of OPC-SO3H which clearly reveals the permeability of the sulfonic acid moieties into it. XPS studies demonstrated that the binding energies of Carbon = 283.6 eV, Sulfur = 168.5 eV and Oxygen = 581.15 eV atoms confirms the presence of -SO3H groups along with carbon powder. The prepared OPC-SO3H powder act as an efficient catalyst for the synthesis of dihydropyrano[2,3-c]pyrazole derivatives via multicomponent reactions. The catalytically synthesized compounds were characterized by FT-IR, 1H NMR and 13C NMR techniques. Use of recyclable OPC-SO3H powder catalyst for the excellent yields with rapid conversion of the targeted dihydropyrano[2,3-c]pyrazole derivatives with simple work-up procedure is the notable advantage of this protocol.