From Racemic Primary Aminoalkyl(phosphanyl)ferrocene Complexes to a Lithium-Phosphorus closo Cluster

摘要

The first chiral phosphanylferrocene, (R)-N,N-dimethyl-1-[(S)-2-(diphenylphosphanyl)ferrocenyl]ethylamine ((R,S)-PPFA), was prepared by Hayashi et al.[1] in 1974 and was successfully applied in homogeneous catalysis two years later.[2] Since then a broad variety of phosphanylferrocene complexes has been synthesized and used for asymmetric reactions, such as hydrogenation, hydrosilylation, and aldol reactions.[3] Studies on the reaction mechanisms have shown that the asymmetric induction is mainly due to the planar chirality of the 1,2-disubstituted ferrocene complexes,[4] for which racemization is hardly possible.