Planar‐Chiral Secondary Ferrocenylphosphanes

An efficient way to obtain pure diastereomeric mixtures of C‐chiral, P‐chiral, planar‐chiral ferrocenylphosphanes is demonstrated by ortho ‐lithiation of enantiomerically pure ( S C )‐ N , N ‐dimethyl‐1‐ferrocenylethylamine (Ugi's amine) and reaction with RPX 2 [X = Cl, Br; R = t Bu, 2,4,6‐Me 3 C 6 H 2 (Mes)]. Four secondary ferrocenylphosphanes [Fe(C 5 H 5 )(1‐PHR‐2‐CHR′NMe 2 ‐C 5 H 3 )] [R′ = H, R = t Bu ( 1 ); R′ = H, R = Mes ( 2 ); R′ = CH 3 , R = t Bu ( 3 ); R′ = CH 3 , R = Mes ( 4 )] were synthesised and characterised. Pure diastereomeric mixtures of 1 and 2 , a mixture of the pure major diastereomers of 4 , as well as diastereomerically pure 3 were obtained by column chromatography under a nitrogen atmosphere. The formation of amine–borane or phosphane–borane adducts was studied by 11 B and 31 P NMR spectroscopy. A theoretical study was performed to understand the tendency of 1 – 4 toward borane adduct formation.