Effect of the Dihedral Angle of Biaryl-Bridged Bisphosphite Ligands on Enantioselectivity and Regioselectivity of Asymmetric Hydroformylation
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- 作者：Christopher J. Cobley ; Robert D. J. Froese ; Jerzy Klosin ; Cheng Qin ; Gregory T. Whiteker ; Khalil A. Abboud
- 刊名：Organometallics
- 出版年：2007
- 出版时间：June 4, 2007
- 年：2007
- 卷：26
- 期：12
- 页码：2986 - 2999
- 全文大小：1388K
- 年卷期：v.26,no.12(June 4, 2007)
- ISSN：1520-6041
文摘
Eight new biaryl-bridged bisphosphite ligands have been synthesized and applied in rhodium-catalyzedasymmetric hydroformylation of styrene, allyl cyanide, and vinyl acetate. X-ray crystallographic studiesof square planar LRh(acac) complexes of four of these bisphosphite ligands revealed that the dihedralangle of the bridging biaryl moiety depends on its identity and lies between 59.8
and 80.0. A correlationbetween the dihedral angle in these Rh complexes and hydroformylation enantioselectivity andregioselectivity for both allyl cyanide and vinyl acetate is reported. Smaller dihedral angles were foundto lead to increased regio- and enantioselectivity. Density functional theory calculations of a five-coordinatemodel complex (LRh(CO)2H) show that decreased dihedral angles lead to smaller P-Rh-P bite angles.Although large bite angles have previously been correlated with increased hydroformylation regioselectivity,these results provide the first demonstration of a bite angle effect on enantioselectivity in asymmetrichydroformylation.
and 80.0. A correlationbetween the dihedral angle in these Rh complexes and hydroformylation enantioselectivity andregioselectivity for both allyl cyanide and vinyl acetate is reported. Smaller dihedral angles were foundto lead to increased regio- and enantioselectivity. Density functional theory calculations of a five-coordinatemodel complex (LRh(CO)2H) show that decreased dihedral angles lead to smaller P-Rh-P bite angles.Although large bite angles have previously been correlated with increased hydroformylation regioselectivity,these results provide the first demonstration of a bite angle effect on enantioselectivity in asymmetrichydroformylation.