Synthesis and structure of planar chiral, bifunctional aminoboronic acid ferrocene derivatives

N,N'-Diisopropylferrocenecarboxamide is utilized for an asymmetric, directed metalation approach to several planar chiral bifunctional ferrocene derivatives. Directed metalation using n-butyllithium-(-)-sparteine on N,N'-diisopropylferrocenecarboxamide can be achieved to give high yields of the corresponding boronic acid; however, it was found that a sequence involving asymmetric directed metalation-bromination, followed by lithium-halogen exchange, was more convenient to access the same derivatives since this allowed straightforward determination of the enantiomeric excess. (pR)-2-[(N,N-Diisopropylamino)methyl]ferrocenylboronic acid and derivatives thereof could be readily accessed with high enantiomeric excess, followed by amide reduction.