Polymer‐Shell‐Encapsulated Magnetite Nanoparticles Bearing Hexamethylenetetramine for Catalysing Aza‐Michael Addition Reactions

Polymer‐encapsulated magnetite nanoparticles bearing Hexamethylenetetramine (Fe3O4@HMTA) have been developed for catalysing the aza‐Michael addition to form β‐amino compounds. The effects of solvent, amount and reuse on catalytic activity of the Fe3O4@HMTA have been studied. The catalytic activity of the Fe3O4@HMTA has not deteriorated during successive recycling. Eight different substrates have been subjected to aza‐Michael additions, and yields of the products in the range of 50–90 % have been observed in the presence of catalyst depending upon the substituent groups in the reactants. The formation of a single chiral adduct by reacting a acrylamide derivative of l‐proline benzyl ester with morpholine seems to suggest that the reaction conditions preclude the racemization of products. A new synthetic route has been developed to form high‐density hexamethylenetetramine‐bearing polymer encapsulation on the magnetically retrievable magnetite nanoparticles to serve as catalyst for the aza‐Michael addition reactions. The synthesis protocol is general and would be useful for loading a variety of homogeneous catalysts.