Grinding Synthesis of 2‐Amino‐4H‐benzo[ b ]pyran Derivatives Catalyzed By Highly Efficient GPTMS/Guanidine Protected Magnetic Nanoparticles**

In this study, we synthesized the GPTMS‐guanidine attached to the magnetic nanoparticles (Fe 3 O 4 @SiO 2 @GPTMS@guanidine) as a novel and efficient heterogeneous nanocatalyst through cheap and available materials. Then, the Fe 3 O 4 @SiO 2 @GPTMS@guanidine nanoparticles were characterized by various analyses such as fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDX), vibrating sample magnetometry (VSM), and Brunauer–Emmett–Teller (BET). The Fe 3 O 4 @SiO 2 @GPTMS@guanidine nanoparticles were used for the effective and green synthesis of 2‐amino‐4 H ‐benzo[ b ]pyran derivatives by grinding method through one‐pot three‐component reactions of dimedone, various aromatic aldehydes and malononitrile at room temperature. Moreover, the reaction in the water as green solvent was checked and acceptable results were obtained. The benefits of these methods include reusability of the Fe 3 O 4 @SiO 2 @GPTMS@guanidine, easy purification, and synthesis of derivatives with high yields and short reaction time. The catalyst has the ability to react up to at least 9 times, without a significant reduction in its activity.