Fe3O4@L-arginine and Fe3O4@L-histidine nanoparticles for one-pot solvent-free sequential Knoevenagel–Michael addition reactions

Fe3O4@L-Arginine and Fe3O4@L-Histidine nanoparticles (NPs) are synthesized and explored as catalysts for the sequential Knoevenagel condensation and Michael addition reactions (KMS). The reaction parameters like the amount of catalyst, temperature, and solvent systems are optimized for both of the catalysts for the Knoevenagel condensation reaction. It was observed that the developed catalyst systems work well under solvent-free conditions at 80 °C. Excellent to high yield was achieved in the corresponding Knoevenagel adducts (up to 97%), in turn, delivered good yield in Michael products (up to 70%). Surprisingly, Fe3O4@L-Hist NPs did not show any catalytic activity for the sequential Michael addition. The probable reasons for the high activities of Fe3O4@L-Arg NPs for KMS have been discussed. The catalyst was also recovered and reused for 5 cycles with equal performance in terms of activity and selectivity. The optimized protocol for sequential Knoevenagel condensation and Michael addition reaction can result in high isolated yields with saving in the cost of solvent and falls under the domain of green chemistry.