Deep eutectic solvents (DESs) are among novel and more eco-friendly alternatives to ionic liquids (ILs) prepared by combining the components and the hydrogen bonds developed between them. The strong hydrogen bond interactions between the constituents of DESs make a considerable decline in the melting points in comparison to pure constituents. These green solvents have unique properties, making them a reliable and safe alternative to ILs and conventional organic solvents. In this study, we investigate the role of Fe3O4 nanoparticles (NPs) in Lactic acid:Melamine:NH4Cl (as a novel deep eutectic solvent) in the green synthesis of pyrido[2,3-d] pyrimidine derivatives. The prepared DES was characterized using FT-IR, 1H NMR, 13C NMR, TGA/DTA, DSC and physical properties, including viscosity, acidity, refractive index, surface tension, and density. The DES used during the experiments plays both catalytic roles and serves as a green environment for this reaction. In addition, magnetic DES can operate under very mild reaction conditions and be recycled easily with no significant catalytic activity loss. The fast and complete synthesis and high yield of the desired product are the remarkable benefits of this catalytic system.
