Salen complex of Cu(II) supported on superparamagnetic Fe3O4@SiO2 nanoparticles: a novel and reusable catalyst for onepot synthesis of Biginelli-type 3,4-dihydropyrimidine- 2-(1H)-ones under solvent-free conditions

An efficient and general method has been developed for synthesis of 3,4-dihydro pyrimidinones under solvent-free conditions using magnetite nanoparticles immobilized Salen Cu(II) as an efficient and recyclable catalyst. This reaction proceeds through acetoacetate esters and aldehyde derivatives followed by cyclisation with a urea to the dihydropyrimidinone. The suggested method offers several advantages such as excellent yields, operational simplicity, a cleaner reaction, and absence of any tedious workup or purification. In addition, the thermal stability, easy preparation and separation of the catalyst make it a good heterogeneous system and a useful alternative to other heterogeneous catalysts. Also, the aforementioned catalyst can be easily recovered by an external magnetic field and reused for subsequent reactions at least 4 times without noticeable deterioration in catalytic activity.

magnetic nanoparticle; heterogeneous catalysts; recyclable catalyst; solvent-free conditions