Highly Enantioselective Nitroaldol Reactions Catalyzed by Copper(II) Complexes Derived from Substituted 2-(Pyridin-2-yl)imidazolidin-4-one Ligands

Ten optically pure substituted 2-(pyridin-2-yl)imidazolidin-4-ones, <b>1a</b>–<b>d</b>, <b>2a</b>–<b>4a</b>, and <b>2b</b>–<b>4</b><b>b</b>, were prepared and characterized. The absolute configurations of individual ligands were determined by X-ray analysis or NOESY experiments. The Cu(II) complexes of the respective ligands were studied as enantioselective catalysts of the nitroaldol (Henry) reaction of aldehydes with nitromethane, giving the corresponding substituted 2-nitroalkanols. In the case of an anti arrangement of the imidazolidin-4-one ring, the obtained result was 91–96% ee, whereas in the case of syn arrangement, a significant drop to 25–27% ee was observed.