Palladium complexes of a chiral P,C-chelating phosphino-(sulfinylmethyl)phosphonium ylide ligand

A new type of phosphino-phosphonium ylide ligand bearing a chiral sulfinyl center affords a P,C-chelated palladium(II) complex with a resolved asymmetric ylidic carbon atom. According to ³¹P NMR analysis of the crude material, the diastereoselectivity of the complexation at room temperature is ca. 7:1. In the crystal state, an X-ray diffraction analysis of one epimer reveals a quasi C₂-symmetric chloro-bridged dinuclear structure, where the (S) configuration of the sulfur atom induces a (S) configuration of the ylidic carbon atom. A in situ Pd(0) catalyst generated from the phosphino-ylide and Pd(PPh₃)₄ promotes allylic substitution of 3-acetoxy-1,3-diphenylpropene by sodium malonate in 70% yield and 5% e.e.