Magnetically recoverable catalyst for the asymmetric Henry reaction based on a substituted imidazolidine-4-one copper(II) complex supported by Fe3O4•SiO2 nanoparticles

The preparation and characterization of a heterogeneous recyclable catalyst based on Cu(II) complex of magnetic nanoparticles Fe3O4 center dot SiO2 with (2R,5S)-5-isopropyl-5-methyl-2-(pyridine-2-y)imidazolidine-4-one is described. The ligand molecules were attached to the surface by means of coordination bonds. The catalyst was characterized using DLS, FT-IR spectroscopy, SEM, and microanalysis. The reaction of substituted aldehydes with nitromethane catalyzed with this complex proceeded with high yields (82-99%) and high enantioselectivity (68-94%). The reaction rate decreased due to the formation of aggregated forms of the catalyst nanoparticles whose size (115-834 nm) depends on their concentration in the reaction medium. After a tenfold recycling of the catalyst, the catalytic activity slightly decreased (similar to 10%); however, no change in enantioselectivity was observed (similar to 94% ee). The efficiency of the catalyst prepared was also verified in the preparation of an intermediate of synthesis of the medical drug (R)-Salmeterol (yield 72%; 91% ee). (C) 2015 Elsevier Ltd. All rights reserved.