Palladium immobilized on functionalized halloysite: A robust catalyst for ligand free Suzuki–Miyaura cross coupling and synthesis of pyrano[2,3-c]pyrazole motifs via four component cascade reaction and their in-silico antitubercular screening

Abstract

This research introduces a novel organically functionalized halloysite-supported palladium catalyst, HMF-EDA-TMS@HAL-Pd(II) that was synthesized and thoroughly characterized using various analytical techniques like HR-TEM, FEG-SEM, EDX, XPS, FTIR, XRD, TGA, ICP-AES, EXAFS and DFT studies. The catalyst exhibited exceptional performance in Suzuki–Miyaura cross coupling reactions, demonstrating high efficiency and reusability up to seven cycles in aqueous ethanol medium. Motivated by its promising catalytic activity, we extended our investigation to explore its applicability in the synthesis of pyrano[2,3-c]pyrazole motifs via a four-component cascade reaction affording the desired products in good to excellent yields with broad substrate scope under green reaction conditions. In-silico antitubercular screening of pyrano[2,3-c]pyrazole motifs against DprE1 enzyme have shown promising results with inhibition constants ranging between 0.030 and 0.1 μM for compounds 5b, 5k and 5 l. This protocol has the advantages of wide substrate scope, high yield, excellent functional group tolerance, high efficiency and environmental benign procedure. These findings emphasized the catalyst's versatility and potential in diverse organic transformations, highlighting its importance in advancing sustainable synthetic methodologies.