Design, Synthesis and Catalytic Activity of (Cyclopentadienone)iron Complexes Containing a Stereogenic Plane and a Stereogenic Axis

Herein, we report the synthesis and characterization of several chiral (cyclopentadienone)iron complexes (CICs) featuring either two (R)-BINOL-derived stereoaxes or a combination of one (R)-BINOL-derived stereoaxis and a stereogenic plane. The stereoplane-containing CICs were obtained as epimer mixtures, which were separated by flash column chromatography and assigned an absolute configuration based on XRD analysis, NMR and order of elution. The library was tested in the asymmetric hydrogenation of ketones showing good catalytic activity and a moderate stereoselectivity which, notably, is mostly imparted by the stereogenic plane. Indeed, the two epimers of each CIC possessing a stereoplane show opposite and equally strong stereochemical preference.Winning plane: chiral (cyclopentadienone)iron complexes (CICs) featuring a combination of an (R)-BINOL-derived stereoaxis and a stereogenic plane were synthesized in diastereoisomerically pure form, characterized and tested in the asymmetric hydrogenation of ketones. The new CICs showed good catalytic activity and, remarkably, the stereoplane epimers displayed similar and opposite stereochemical preference.