Abstract
This research dealt with preparation of magnetically separable Ag/Fe3O4/rGO nanocomposite through green method using Mangrove tree aerial root extract as a stabilising agent. The morphology, size, chemical composition, magnetic property and other characteristic parameters of synthesized Ag/Fe3O4/GO nanocomposite were determined by analytical techniques like FT-IR, XRD, EDX and SEM. The results proved that the Mangrove tree aerial root extract has the ability of reduction of Ag+ ions and graphene oxide (GO) to Ag nanoparticles and reduced graphene oxide (rGO), respectively. The prepared Ag/Fe3O4/rGO nanocomposite is used successfully as a prompt catalyst for synthesis of 7-phenyl-6H,7H-benzo[4,5]imidazo[2,1-b]chromeno[4,3-d][1,3]thiazin-6-one derivatives by one-pot multicomponent reaction of hydroxycoumarin (10 mmol), mercaptobenzimidazole (10 mmol) and different aldehyde (10 mmol) in the presence of ethanol (10 ml) as an eco-benign solvent at reflux condition. By utilising this protocol, we have constructed 7-phenyl-6H,7H-benzo[4,5]imidazo[2,1-b]chromeno[4,3-d][1,3]thiazin-6-one derivatives in good to excellent yield of 80-90%. This synthesis involves formation for C-C, C-N, C-S bond. The synthesized organic heterocyclic compounds were examined for the green matrix properties such as atom economy (AE), E-factor and product mass intensity (PMI). This green protocol is of big interest due to employing simple, non-toxic heterogeneous, separable, reusable Ag/Fe3O4/GO as an eco-safe heterogenous catalyst and environmentally benign ethanol as a green solvent without the use of any harmful mineral acid and toxic transition metal catalyst.