Optically active microspheres from helical substituted polyacetylene with pendent ferrocenyl amino-acid derivative. Preparation and recycling use for direct asymmetric aldol reaction in water

摘要

The contribution reports a novel type of chiral microspheres in which ferrocenyl amino-acid derived catalytic moieties were integrated with optically active helical substituted polyacetylene. The microspheres were prepared by suspension copolymerization of achirally and chirally substituted acetylenic monomers in a quantitative yield. SEM images showed the microspheres' regular spherical morphology. Circular dichroism and UV-vis absorption spectra demonstrated that the copolymer chains constituting the microspheres adopted predominantly one-handed helices, endowing the microspheres with optical activity. The microspheres were further used to catalyze aldol reaction between cyclohexanone and pnitrobenzaldehyde in water media in the presence of Brosted acid, providing the product with remarkable yield (up to 91%) and enantiomeric excess (up to 93%). Synergistic effects occurred in the helical polymer chains and the pendant catalytic moieties. The catalytic microspheres can be finely recycled and reused three times without significant loss of catalytic ability and enantio-selectivity. (C) 2017 Elsevier Ltd. All rights reserved.