Chiral P,S-Ligands Based on β- 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)lthio)-β- d -glucopyranose, [(2-Ph 2 PC 6 H 4 CH 2 )SCHCH(OAc)CH(OAc)CH(OAc)CH(CH 2 OAc)O, 2 ] and 2,3,4,6-tetra- O -acetyl-1-((2-(dicyclohexylphosphino)benzyl)thio)-β- d -glucopyranose [(2-Cy 2 PC 6 H 4 CH 2 )SCHCH(OAc)CH(OAc)CH(OAc)CH(CH 2 OAc)O,, 3 ] as well as their (1,3-diphenylallyl)palladium(II) cationic complexes [Pd(η 3 -PhCHCHCHPh)( 2 )]PF 6, 6, and [Pd(η 3 -PhCHCHCHPh)( 3 )]PF 6, 7, and one η 3 -C 3 H 5 complex [Pd(η 3 -C 3 H 5 )( 2 )]PF 6, 5, have been prepared. The solid-state structure of [Pd(η 3 -C 3 H 5 )( 2 )]PF 6, 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.