Immobilized Gelatin-λ-Carrageenan on Magnetite Nanoparticles as an Efficient Organocatalyst for Enantioselective Biginelli Reaction

A facile method for preparation of stabilized and functionalized nanoparticles (NPs) from magnetite by successive application of blended natural polymers (gelatin and lambda-carrageenan) on Fe3O4 core has been developed. Gelatin plays a privileged role in the catalytic active sites and it is responsible for the enantiomeric induction. lambda-carrageenan endowed chemical stability for immobilization of gelatin on Fe3O4 nanoparticles, thereby enhancing its stability and recoverability. The versatility of the modified NPs was proved by their excellent heterogeneous catalytic activity in one-pot, three-component Biginelli cyclocondensation reaction involving an aromatic aldehyde, urea, and ethyl acetoacetate (or Dimedone) to afford optically active corresponding dihydropyrimidinones in acceptable yields. This novel and green protocol has several advantages such as high efficiency, reusability of the catalyst, using inexpensive and available compounds for the catalyst.