The new chelating P,S-ligands 2,3,4,6-tetra-O-acetyl-1-((2-(diphenylphosphino)benzy)lthio)- â-D-glucopyranose, [(2-Ph2PC6H4CH2)SCHCH(OAc)CH(OAc)CH(OAc)CH(CH2OAc)O, 2] and 2,3,4,6-tetra-O-acetyl-1-((2-(dicyclohexylphosphino)benzyl)thio)-â-D-glucopyranose [(2-Cy2- PC6H4CH2)SCHCH(OAc)CH(OAc)CH(OAc)CH(CH2OAc)O,, 3] as well as their (1,3-diphenylallyl) palladium(II) cationic complexes [Pd(è3-PhCHCHCHPh)(2)]PF6, 6, and [Pd(è3- PhCHCHCHPh)(3)]PF6, 7, and one è3-C3H5 complex [Pd(è3-C3H5)(2)]PF6, 5, have been prepared. The solid-state structure of [Pd(è3-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.
Chiral P,S-Ligands Based on ?-d-Thioglucose Tetraacetate. Palladium(II) Complexes and Allylic Alkylation
Barbaro Pierluigi;
1996
Abstract
The new chelating P,S-ligands 2,3,4,6-tetra-O-acetyl-1-((2-(diphenylphosphino)benzy)lthio)- â-D-glucopyranose, [(2-Ph2PC6H4CH2)SCHCH(OAc)CH(OAc)CH(OAc)CH(CH2OAc)O, 2] and 2,3,4,6-tetra-O-acetyl-1-((2-(dicyclohexylphosphino)benzyl)thio)-â-D-glucopyranose [(2-Cy2- PC6H4CH2)SCHCH(OAc)CH(OAc)CH(OAc)CH(CH2OAc)O,, 3] as well as their (1,3-diphenylallyl) palladium(II) cationic complexes [Pd(è3-PhCHCHCHPh)(2)]PF6, 6, and [Pd(è3- PhCHCHCHPh)(3)]PF6, 7, and one è3-C3H5 complex [Pd(è3-C3H5)(2)]PF6, 5, have been prepared. The solid-state structure of [Pd(è3-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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
