Synthesis of efficient chiral bisphosphine ligands, modified DIOPs, (4R,5R)-4-(Diaryl- or dialkylphosphino)methyl-5-(diarylphosphino)methyl-2,2- dimethyl-1,3-dioxolanes, and their use in rhodium(I)-catalyzed asymmetric hydrogenations

Article abstract of DOI:10.1248/cpb.41.1149

Modified DIOPs, (4R,5R)-4-(diaryl- or dialkyphosphino)methyl-5- (diarylphosphino)methyl-2,2-dimethyl-1,3-dioxolanes, were prepared on the basis of our design concept, and used as ligands for the rhodium(I)-catalyzed asymmetric hydrogenations of ketopantolactone, itaconic acid, dimethyl itaconate, and β-aryl-substituted itaconic acid derivatives. A neutral rhodium(I)-complex of (4R-trans)-dicyclohexyl[[5- [(diphenylphosphino)methyl]-2,2-dimethyl-1,3-dioxolan-4-yl]methyl]phosphine (DIOCP) bearing both a dicyclohexylphosphino group and a diphenylphosphino group was found to be a more efficient catalyst than the original DIOP in the asymmetric hydrogenation of ketopantolactone. Modified DIOPs bearing electron-donating groups at their para positions were efficient ligands for the rhodium(I)-catalyzed assymetric hydrogenations of itaconic acid and its derivatives; in particular, (4R-trans)-[(2,2-dimethyl-1,3-dioxolane-4,5- diyl)bis(methylene)]bis[bis(4'-methoxy-3',5'-dimethylphenyl)phosphine] (MOD- DIOP) bearing both a p-methoxy group and two m,m'-methyl groups on each phenyl group showed much higher enantioselectivity and catalytic activity than DIOP.

Full text of DOI:10.1248/cpb.41.1149

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