Preparation of functionalized magnetic nanoparticles bearing sulfonic acid as an effective reusable solid acid catalyst for the synthesis of benzothiazoles

In this study, solid acid magnetic nanoparticles Fe₃O₄@SiO₂-S-Bu-SO₃H were prepared under appropriate conditions and characterized by various analytical techniques including FT-IR, XRD, FE-SEM, EDX, and VSM. Finally, the catalytic activity of the synthesized Fe₃O₄@SiO₂-S-Bu-SO₃H MNPs was investigated for the synthesis of valuable benzothiazole derivatives by the condensation reaction of ortho-aminothiophenol and various aldehydes under ultrasonic conditions. In the presence of the inexpensive, environment-friendly, magnetically recoverable solid acid catalyst, the benzothiazoles were obtained as pure target products in excellent yields (90–98%) and short reaction times (3–11 min). The synthesized Fe₃O₄@SiO₂-S-Bu-SO₃H MNPs show great catalytic activity because of the combined effect of Brønsted acidity and high functional group density. This solid acid magnetic nanocatalyst is reusable for several cycles and can be easily segregated from the reaction mixture.