Fe ₃ O ₄ @SiO ₂ ‐APA‐Amide/Imid‐NiCl ₂ as a New Nano‐Magnetic Catalyst for the Synthesis of 4 <i>H</i> ‐Pyrimido[2,1‐ <i>b</i> ]benzothiazole Derivatives via MCRs Under Solvent‐Free Conditions

Abstract This study presents the synthesis and characterization of a novel nano‐magnetic catalyst, Fe 3 O 4 @SiO 2 ‐APA‐amide/imid‐NiCl 2 , designed for the efficient production of 4 H ‐pyrimido[2,1‐ b ]benzothiazole derivatives under environmentally friendly, solvent‐free conditions. The catalyst combines magnetic Fe 3 O 4 nanoparticles with a silica shell and functionalized amide and imidazole groups, which enhance its catalytic activity and stability. By optimizing the reaction conditions, we achieved high yields of the target compounds while minimizing the environmental impact. The catalyst's magnetic properties facilitate easy separation and recovery, making it an attractive option for sustainable organic synthesis. The successful synthesis of the catalyst was confirmed through comprehensive characterization techniques, including X‐ray diffraction (XRD), Fourier‐transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The results demonstrate that Fe 3 O 4 @SiO 2 ‐APA‐amide/imid‐NiCl 2 is a highly effective and reusable catalyst for the environmentally friendly synthesis of biologically relevant pyrimido[2,1‐b]benzothiazole derivatives, contributing to the advancement of green methodologies in organic chemistry.