Chiral C(2)-symmetric ligands with 1,4-dioxane backbone derived from tartrates: syntheses and applications in asymmetric hydrogenation.
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.
Li
Wenge
W
Department of Chemistry, The Pennsylvania State University, University Park 16802, USA.
Waldkirch
Jason P
JP
Zhang
Xumu
X
D004146:Dioxanes / Q000737:chemistry*; D006865:Hydrogenation; D008024:Ligands; D015394:Molecular Structure; D013237:Stereoisomerism; D013644:Tartrates / Q000737:chemistry*
D004146:Dioxanes; D008024:Ligands; D013644:Tartrates; C025223:1,4-dioxane; C029768:tartaric acid