Axially chiral P,S-heterodonor ligands with a binaphthalene framework for palladium-catalyzed asymmetric allylic substitutions: experimental investigation on the reversal of enantioselectivity between different alkyl groups on sulfur atom

The enantioselectivity in the palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenylpropenyl acetate with dimethyl malonate using axially chiral P,S-heterodonor ligands BINAPS with different alkyl groups on sulfur atom has been investigated. Their bidentate coordination patterns to a Pd metal center with both P and S atoms have been unambiguously disclosed by X-ray diffraction. The reaction mechanism and the investigation on the reversal of enantioselectivity between different alkyl groups on sulfur atom have been discussed on the basis of the X-ray crystal structure and NMR spectroscopic data.