Synthesis and Application of Fe3O4@RHA@MEL-SO3H Nanocatalyst in the Synthesis of 1-amidoalkyl-2-naphthols through a Statistical Approach to Optimize the Reaction Conditions

The future age of sustainable development in organic synthesis requires natural sources with properties such as cost-effectiveness, biodegradability, availability, durability, and environmentally friendly resources. An instance of material that has these favorable properties is the rice husk ash (RHA) covered the Fe3O4 nanoparticles, followed by melamine sulfonic acid immobilization. In this study, rice husk ash was obtained, and then by adding Fe3O4, melamine, and ClSO3H in different stages and with different solvents, Fe3O4@RHA@MEL-SO3H nanocatalyst was prepared as a solid acid and characterized using TGA, FT-IR, EDX, VSM, Fe-SEM, and XRD methods. Then, the use of Fe3O4@RHA@MEL-SO3H catalyst as a green nanocatalyst for 1-amidoalkyl-2-naphthols preparation via multi-component condensation of benzamide, aromatic aldehydes, and 2-naphthol in solvent-free conditions was investigated. Considering the important parameters (temperature, reaction time, and catalyst amount) in the reaction since experimental design increase process efficiency, and decrease cost and experimental time, this is the successful technique for the effects of their variables and their interactions. The experimental design was performed to optimize the reaction conditions, and the effect of the three parameters, namely, temperature, reaction time, and catalyst amount were investigated by the response surface methodology (RSM). This study showed that the heterogeneous nanocatalyst has the advantage of being recyclable, which is no trouble separated from the reaction mixture by an external magnet and can be reused up to 9 times; it also has a high product yield, short reaction time, and environmentally and economically good performance.