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 M-3[Ln(binol)(3)] (M = Li; Ln = lanthanide; H(2)binol = binaphthol) mediate the addition of RLi to aldehydes with ee's 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. [LnCl(3)(pybox)(2)] are effective catalysts for the silylcyanation of aldehydes, giving ee's of up to 89% under convenient reaction conditions. Structural studies have been undertaken on [Ln(OTf)(3)(Pr'-pybox)(2)] for Ln = La, Eu or Yb. (C) 2002 Elsevier Science B.V. All rights reserved.