Fe3O4@SiO2 supported vanillin/Indole-sulfonic acid as a green, sustainable and magnetically reusable catalyst for the synthesis of mono-, bis- and tris- azo acridines

Fe3O4@SiO2 supported vanillin/Indole-sulfonic acid (Fe3O4@SiO2Pr@Vanillin@Indole-sulfonic acid) nanoparticles were synthesized and were characterized by FE-SEM, FT-IR, XRD, VSM, TEM, EDX, and TGA-DTG. Then, the application of this new nano catalyst for the multicomponent synthesis of azo-derived dihydropyridines via the reaction of azo-linked aldehydes, dimedone, and ammonium acetate was investigated. The procedure was carried out in high yields and short reaction times. Easy preparation of the catalyst and easy work-up are the main advantages of the protocol. The nanocatalyst can be reused for six reaction cycles with no notable decrease in catalytic efficiency. It is the first report to use Fe3O4@SiO2Pr@Vanillin@Indole-sulfonic acid for the synthesis of azoacridines. All of the organic compounds synthesized are new and were characterized carefully. The reaction times and yields for the synthesis of azoacridines are comparable to the reported methods for the synthesis of simple acridines. The reaction speed is suitable, and the productivity of this method is good. The reaction was carried out under solvent-free conditions and in green and mild conditions. The methodology described is completely new. The highlighted points of this work are as follows: 1) All of the synthesized azo-linked acridines are new. 2) The catalyst synthesized is completely new. 3) There is the first report for the synthesis of azo-linked dihydropyridines using Fe3O4@SiO2 supported vanillin/Indole-sulfonic acid. 4) Shorter reaction times and higher yields, rather than most of the reported methods, are two major benefits of this work. 5) The reaction was carried out under solvent-free conditions, and there is no need to use organic and hazardous solvents in this procedure. 6) The reaction was carried out at room temperature, which requires no heating, and it is based on green chemistry rules because the method is energy-efficient. Research Highlights • Fe3O4@SiO2Pr@Vanillin@Indole-sulfonic acid were synthesized as new nanomaterials. • It is the first report to use Fe3O4@SiO2Pr@Vanillin@Indole-sulfonic acid for the synthesis of azoacridines. • Mono, bis and tris azoacridines, most of them are new and were characterized completely. • This reaction under solvent-free method is based on green chemistry rules and is environmentally freindly procedure. • The catalyst is magnetically recoverable and it is economically safe.