Defining effective chiral binding sites at lanthanides—highly enantioselective reagents and catalysts from binaphtholate and pybox ligands

This paper reviews our work with enantioselective lanthanide reagents and catalysts for organic synthesis. Heterometallic reagents M3[Ln(binol)3] (M=Li; Ln=lanthanide; H2binol=binaphthol) mediate the addition of RLi to aldehydes with eeʹs of up to 84%. Structural studies have been carried out where M=Li or Na, Ln=Eu, Y or Yb and with enantiomerically pure or racemic binol. There are important differences in coordination chemistry dependent on the ionic radius of M and Ln. [LnCl3(pybox)2] are effective catalysts for the silylcyanation of aldehydes, giving eeʹs of up to 89% under convenient reaction conditions. Structural studies have been undertaken on [Ln(OTf)3(Pripybox)2] for Ln=La, Eu or Yb.