- 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
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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.
- Morimoto,Chiba,Achiwa
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p. 1149 - 1156
(2007/10/02)
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- CATALYTIC ASYMMETRIC HYDROGENATION WITH RHODIUM COMPLEXES OF IMPROVED DIOPS BEARING PARA-DIMETHYLAMINO GROUP ON THE BASIS OF OUR DESIGNING CONCEPT
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Unsymmetrized and symmetrized DIOP analogues bearing para-dimethylamino group have been synthesized to prove the general utility of our designing concept for developing highly effective catalysts.Their rhodium complexes have been shown to be much more effective in the asymmetric hydrogenations than that of DIOP.
- Morimoto, Toshiaki,Chiba, Mitsuo,Achiwa, Kazuo
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p. 4755 - 4758
(2007/10/02)
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