Optically active,magnetic microspheres: Constructed by helical substituted polyacetylene with pendent prolineamide groups and applied as catalyst for Aldol reaction

This article reports on the preparation of a novel category of optically active magnetic microspheres (OAMMPs) consisting of Fe₃O₄ nanoparticles and helical substituted polyacetylene bearing pendent prolineamide groups and the use of them for asymmetric direct Aldol reactions. The microspheres (200–300 μm in diameter) were prepared by using chiral acetylenic monomer and alkynyl-Fe₃O₄ nanoparticles via suspension polymerization approach. They were obtained in high yield (> 99%) with regular spheric morphology and exhibited noticeable optical activity, according to circular dichroism spectra and specific optical rotation measurements. The microspheres further served as chiral catalyst for performing direct Aldol reactions between acetone and p-nitrobenzaldehyde, providing the product in moderate yield (68%) and ee (75%). The magnetic microspheres can be easily recycled and reused. Mechanism for the asymmetric catalysis of Aldol reaction was further proposed.