Synthesis of Ferrocene Oxazoline N,O ligands and Their Application in Asymmetric Ethyl- and Phenylzinc Additions to Aldehydes

The synthesis of a range of novel <i>gem</i>-disubstituted ferrocene–oxazoline ligands and their application in both the asymmetric ethyl- and phenylzinc additions to aldehydes is reported. These studies reveal that <i>gem</i>-disubstitution of <i>i</i>-Pr-containing ferrocene oxazoline ligands results in increased enantioselectivity compared to their unsubstituted counterparts. Utilizing zinc catalysis, these ligands provided a wide range of secondary alcohols in yields of up to 93% with ee’s of up to >99%. An interesting crystal structure of a ferrocene oxide–lithium tetramer showing lithium–nitrogen coordination in the solid state is also presented