Planar chiral alkenylferrocene phosphanes: Preparation, structural characterisation and catalytic use in asymmetric allylic alkylation

Planar chiral alkenylferrocene phosphanes (Sp)-[Fe(η5-C5H3-1-PPh2-2-CHCR2)(η5-C5H5)] (R = H, Ph) and (Sp)-[Fe(η5-C5H3-1-PPh2-2-(E)-CHCHR)(η5-C5H5)] (R = Ph, C(O)CH3, and CO2Et) form active catalysts for asymmetric palladium-catalysed allylic alkylation of 1,3-diphenylprop-2-en-1-yl acetate with dimethyl malonate. However, the ee's are only modest (12-43%) and strongly depend on the properties of the double bond substitutents. The mechanism of stereodiscrimination is discussed in view of the solution and solid-state structural data for the cationic complex [Pd(η3-Ph2C3H3){(Sp)-[Fe(η5-C5H3-1-PPh2-2-CHCH2)(η5-C5H5)]-η2:κP}]ClO4.