Hybrid magnetic materials (Fe3O4-k-carrageenan) as catalysts for the Michael addition of aldehydes to nitroalkenes

Two hybrid magnetic materials have been prepared from κ-carrageenan and Fe₃O₄ nanoparticles and tested as catalysts for the Michael addition of aldehydes to nitroalkenes. Remarkably, the material prepared from unmodified κ-carrageenan showed catalytic activity in the reaction of choice, while the individual components were inactive. This points out to a synergistic effect between the MNPs and κ-carrageenan. The second catalyst, bearing a diphenylprolinol silyl ether moiety, was also shown to promote the reaction, giving rise to the corresponding adducts in excellent ees. After the reaction is complete, the catalysts can be conveniently retrieved by simple magnetic decantation.