Synthesis of Thermoregulated Noyori Ligand and Its Application in Asymmetric Transfer Hydrogenation of Acetophenone

Abstract

Abstract: A novel poly(ethylene glycol) chain modified thermoregulated Noyori ligand was designed and synthesized. Its Ru complex was used as a catalyst in the asymmetric transfer hydrogenation of acetophenone in aqueous/cyclohexane biphasic system with sodium formate as hydrogen source. The effects of reaction temperature, reaction time, the amounts of sodium formate, molar ratio of acetophenone to catalyst and the volume of organic solvent on the enantioselective catalytic hydrogenation of acetophenone were investigated. The results reveal that the catalyst containing aqueous phase possesses cloud point and the complex catalyst is effective and highly enantioselective for the asymmetric transfer hydrogenation of acetophenone. With a n(HCO₂Na)∶n(acetophenone)∶n(catalyst)=300∶100∶1 in a n(cyclohexane)∶n(water)=1∶1 reaction medium, the reaction runs at 30 ℃ for 6 h to give the results that the conversion of acetophenone is 99.7% and the e.e. value of the product α-phenylethanol is 93.9%. The aqueous phase containing catalyst can be easily separated from the organic phase and reused for consecutive reaction directly. During recycling, the catalyst activity decreases obviously each time whereas the enantioselectivity of the product is unchanged.

Key words: Polyethylene glycol monomethyl ether(MPEG), Noyori ligand, Aqueous/organic biphasic system, Asymmetric transfer hydrogenation, Acetophenone

TrendMD:

MING Yan-Hua, FAN Ai-Li, JIN Zi-Lin, JIANG Jing-Yang*. Synthesis of Thermoregulated Noyori Ligand and Its Application in Asymmetric Transfer Hydrogenation of Acetophenone[J]. Chem. J. Chinese Universities, 2010, 31(8): 1548.

References

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