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

Planar chiral alkenylferrocene phosphanes, viz. (Sp)-[Fe(eta(5)-C5H3-1-PPh2-2-CH=CR2)(eta(5) -C5H5)] (R H, (S-p)-2; Ph, (S-p)-5) and (S-p)-[Fe(eta(5)-C5H3-1-PPh2-2-(E)-CH=CHR)(eta(5)-C5H5)] (R = Ph, (S-p)-3; C(O)CH3, (S-p)-6; and CO2CH2CH3, (Sp)-7) have been prepared by alkenylation of (S-p)-2-(diphenylphosphanyl)ferrocenecarboxaldehyde and tested as ligands for enantio selective palladium-catalysed allylic alkylation of 1,3-diphenyprop-2-en-1-yl acetate with dimethyl malonate. All phosphanylalkenes formed active catalysts. However, the induced enantioselectivity was only poor to moderate [12-43% ee after 20 It at room temperature], with the ee's and configuration of the preferred product strongly depending on the ligand structure. The catalytic results have been related to solution properties (NMR, ESI MS) and the solid-state structural data (X-ray diffraction) of [Pd(eta(3)-1,3-Ph2C3H3){(S-p)-2-eta(2):kappa P}]ClO4 ((S-p)-12), which represent a model of the plausible reaction intermediate. (C) 2007 Elsevier B.V. All rights reserved.