A Ferrocene-Based Phosphane/Borane Frustrated Lewis Pair for Asymmetric Imine Reduction.

The α-phosphanylferrocenecarbaldehyde ( pS)- 1 was converted into the β-styryl derivative ( pS)- 4 by Wittig-Horner olefination. Subsequent hydroboration with Piers' borane [HB(C6F5)2] followed by H2 splitting and crystallization gave the phosphonium/hydridoborate product ( pS, R)- 5, which was used as a frustrated Lewis pair catalyst for the asymmetric hydrogenation of a series of imines (up to 69 % ee). [ABSTRACT FROM AUTHOR]