Unravelling the catalytic potential of a magnetic CoFe2O4/Cu–ABDC MOF composite in the sustainable synthesis of 2H-indazole motifs

Abstract

Incessant advancements made in catalytic processes during the past few decades prompted researchers to design prodigious sustainable materials that lie within the domain of green synthesis. From this perspective, metal organic frameworks (MOFs) with abundant chemical functionalities and ultra-high chemical as well as structural tunability have emerged as the most prolific heterogeneous catalysts in synthetic organic chemistry. Herein, we report the fabrication of a magnetic CoFe₂O₄/Cu–ABDC (ABDC = 2-aminoterephthalate) hybrid composite via a one-pot solvothermal strategy whose catalytic efficiency has been investigated in a three-component coupling reaction to obtain biologically active and pharmacologically significant 2H-indazole scaffolds (up to 98% yield). By integrating magnetic inverse spinel cobalt ferrite nanoparticles with the functional properties of the MOF, two most important parameters, i.e. environmental compatibility and recyclability, have been well established on a single platform. Aided by the advanced microscopic, spectroscopic and property characterization tools, the morphological as well as structural information of the developed hybrid composite has been deduced well. The aim of this study is to design a sustainably viable process that would provide highly demanding pharmacophores, i.e. 2H-indazoles, in surprisingly high yields from comparatively cheap benchmark substrates – “substituted anilines, 2-bromobenzaldehydes and sodium azide”. Furthermore, our protocol has successfully accomplished the remarkable task of replacing toxic volatile organic solvents with eco-friendly solvents such as water. A broad substrate scope, high atom economy, ambient and greener reaction conditions devoid of any ligands, additives or activators, a lower reaction time and temperature, a high turnover frequency and magnetic retrievability are some of the salient features of this methodology which render it highly promising in industry and academia. Besides, the present study is the first report employing a magnetic MOF as a heterogeneous catalyst for the preparation of 2H-indazole moieties.