Heterogeneous asymmetric hydroformylation of olefins on chirally modified Rh/SiO₂ catalysts

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• 作者：Difei Han ; Xiaohong Li ; Huidong Zhang ; Zhimin Liu ; Jun Li and Can Li
• 关键词：Heterogeneous catalysis ; Enantioselective hydroformylation ; Chiral modification ; Coordination ; Phosphorus ligands
• 刊名：Journal of Catalysis
• 出版年：2006
• 期刊代码：97_00219517
• 类别：ce
• 出版时间：25 October 2006
• 卷：243
• 期：2
• 页码：318-328
• 文件大小：356 K

摘要

Heterogeneous chiral catalysts were prepared by modifying silica-supported rhodium (Rh/SiO₂) with chiral phosphorus ligands. The chirally modified Rh/SiO₂ catalysts exhibited high activity, regioselectivity, and enantioselectivity for the asymmetric hydroformylation of styrene and vinyl acetate. Up to 72%ee and 100%selectivity of branched aldehyde for the hydroformylation of vinyl acetate were obtained for (R)-BINAP–Rh/SiO₂ catalysts. It is noteworthy that the modification of Rh/SiO₂ with (S,S)-DIOP resulted in increased activity for the hydroformylation of vinyl acetate and gave a TOF of 128 h⁻¹, even higher than that of the unmodified Rh/SiO₂ catalyst (90 h⁻¹). It is found that chiral modifiers with bidentate phosphines and an optimized modifier/rhodium molar ratio close to 1.0 were prerequisites for chiral induction on the chirally modified catalysts. MAS NMR results and IR spectra of adsorbed CO indicated that the chiral modification via the coordination of phosphines to rhodium produces chirally active sites on the Rh/SiO₂ catalysts.