Agar-coated Fe3O4 nanoparticles (Fe3O4@agar) were prepared simply through in situ co-precipitation of Fe2+ and Fe3+ ions via NH4OH in an aqueous solution of Agar. Coating of Ag+ ions on the surface of the latter followed by mild reduction of Ag+ with NaBH4 gives Fe3O4@Agar-Ag NPs. The magnetic Fe3O4@Agar-Ag nanocatalyst was characterized thoroughly by FT‐IR, XRD, SEM, TEM, VSM, EDX, TGA, and ICP analyses. Its catalytic activity was assessed in the synthesis of 12-aryl-8,9,10,12-tetrahydrobenzo[a]xanthene-11-one, 14-aryl-14H-dibenzo[a,j]xanthenes, and 1,8-dioxo-octahydroxanthene derivatives through a one-pot condensation of dimedone, 2-naphthol, and aryl aldehydes in EtOH. This novel method represents lots of advantages compared to the previous researches, such as avoiding the toxic catalysts, easy method for isolation of the products, satisfying yields, totally clean conditions, and simplicity of the methodology. This catalytic system is attributed to an eco-friendly process, high catalytic activity, and facility of recovery using an external magnet.

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