SiO ₂ /Fe ₃ O ₄ @MWCNTs Promoted Green Synthesis of Functionalized Thiazinonaphthyridines Using Multicomponent Reactions

This manuscript elucidates a methodology for the synthesis of thiazinonaphthyridine employing benzaldehydes, malononitrile, thiophenol, acetylenic esters, and isothiocyanates. The synthetic process is conducted at ambient temperature devoid of solvent utilization, employing a recyclable catalyst designated as SiO 2 /Fe 3 O 4 @MWCNTs, which yields favorable results. It is imperative to note that the exceptional efficacy of the synthesized nanocatalyst was achieved through the utilization of an aqueous extract derived from the leaves of Petasites hybridus , which was employed in these reactions multiple times to ascertain the reusability of the nanocatalyst. The antioxidant properties of the newly synthesized thiazinonaphthyridine can be attributed to the presence of the NH group, which was assessed through two methodologies known as diphenyl‐picrylhydrazine (DPPH) radical trapping and the Ferric ions (Fe 3+ ) reducing potential (FRAP) assay. Compound 6b exhibited superior efficacy when evaluated against BHT and TBHQ among the thiazinonaphthyridine derivatives 6a–6d that were analyzed. Furthermore, the antimicrobial efficacy of the newly produced thiazinonaphthyridine was examined through a disk diffusion method involving two distinct strains of Gram‐negative and Gram‐positive bacteria from which thiazinonaphthyridine derivatives 6a , 6d , 6e , 6g , and 6j exhibit significant antibacterial activity against Escherichia coli , presumably attributable to the considerable breadth of the zone of inhibition. The methodology employed for the synthesis of thiazinonaphthyridine derivatives presents advantages such as reduced reaction times, high product yields, and the feasibility of separating the catalyst from the products through a straightforward procedure.