ortho-Silylation of 2,2′-bis(oxazolinyl)-1,1′-bis(diphenylphosphino)ferrocenes and remarkable effect of the silyl groups on the enantioselectivity in Pd-catalyzed asymmetric allylic alkylation

ortho-Silylation of chiral 2,2′-bis(oxazolinyl)-1,1′-bis(diphenylphosphino)ferrocenes (1) provided monosilylated derivatives, which were employed as chiral ligands in the Pd-catalyzed asymmetric allylic alkylation of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate. The major product has (S)-configuration in the reactions employing three diastereomers 1 and the monosilylated ligand derived from the (S,S,PS,PS)-diastereomer (up to 99% ee). In sharp contrast, the enantioselectivity was reversed to give (R)-product in the reactions with the ligands derived from the (S,S,PR,PR)-diastereomer (up to 96% ee).