Chiral P,S-ligands based on beta-d-thioglucose tetraacetate. Palladium(II) complexes and allylic alkylation

The new chelating P,S-ligands 2,3,4,6-tetra-O-acetyl-1-((2-(diphenylphosphino)benzy)]thio)-beta-D-glucopyranose, [(2-Ph(2)PC(6)H(4)CH(2))SCHCH(OAc)CH(OAc)CH(OAc) CH(CH2OAc)O, 2] and 2,3,4,6-tetra-O-acetyl-1-((2-(dicyclohexylphosphino)benzyl)thio)-beta-D-glucopyranose [(2-Cy(2)-PC6H4CH2)SCHCH(OAc)CH(OAc)CH(OAc)CH(CH2OAc)O,, 3] as well as their (1,3-diphenylallyl)palladium(II) cationic complexes [Pd(eta(3)-PhCHCHCHPh)(2)]PF6, 6, and [Pd(eta(3)-PhCHCHCHPh)(3)]PF6, 7, and one eta(3)-C3H5 complex [Pd(eta(3)-C3H5)(2)]PF6, 5, have been prepared. The solid-state structure of [Pd(eta(3)-C3H5)(2)]PF6, 5, has been determined by X-ray diffraction methods and found to have the S-sugar substituent and one of the P-phenyl rings in pseudo-axial positions on the same side of the P-Pd-S coordination plane. Detailed NMR measurements for 6 reveal the presence of two diastereomeric isomers whereas for 7 four diastereomers are found. 2-D exchange NMR is used to characterize several of the selective equilibria within 6 and 7. On the basis of the observed ee in the enantioselective homogeneous allylic alkylation of 7, it is suggested that the reaction kinetics for the four isomers are not all the same.