title: Chiral C(2)-symmetric ligands with 1,4-dioxane backbone derived from tartrates: syntheses and applications in asymmetric hydrogenation.
abstract: Chiral 1,4-diphenylphosphines 5-7 as well as thioether 8 were synthesized from tartrates employing Ley's "BDA" and "Dispoke" methodologies as the key step. Rhodium(I) complexes with 5-7 are efficient catalysts for the asymmetric hydrogenation of beta-substituted enamides and MOM-protected beta-hydroxyl enamides, which furnished chiral amines or beta-amino alcohols with 94-->99% ee. These results indicated that the 1,4-dioxane backbone in the ligands having the general structure 2 played an important role in stabilizing metal-ligand chelate conformation. Higher enantioselectivities with ligand 2 were achieved compared with the analogous ligands having the general structure 1.
authors.affiliation: Department of Chemistry, The Pennsylvania State University, University Park 16802, USA.
authors.forename: Wenge
authors.initials: W
authors.lastname: Li
authors.forename: Jason P
authors.initials: JP
authors.lastname: Waldkirch
authors.forename: Xumu
authors.initials: X
authors.lastname: Zhang
mesh_terms: D004146:Dioxanes / Q000737:chemistry*; D006865:Hydrogenation; D008024:Ligands; D015394:Molecular Structure; D013237:Stereoisomerism; D013644:Tartrates / Q000737:chemistry*
chemical_list: D004146:Dioxanes; D008024:Ligands; D013644:Tartrates; C025223:1,4-dioxane; C029768:tartaric acid