Asymmetric hydrogenation ofα-ketoesters plays an important role in the synthesis of pharmaceuticals and other chemicals.Among different catalysts,chiral transition metal nanocatalysts are widely used in this asymmetric hydrogenation reaction.However,it is still a major challenge to achieve the separation and recycling of expensive chiral transition metal nanocatalysts.Therefore,in this thesis,a new chiral catalytic system was established to achieve the separation and recycling of chiral transition-metal nanocatalysts with high enantioselectivity.The main results are as follows:Two new chiral ionic liquids CILTPT-1[CH3(OCH2CH2)16CD]+[PF6]-and CILTPT-2[CH3(OCH2CH2)16CD]+[N(SO2CF3)2]-(CD=cinchonidine)with the character of cloud point(Cp)were designed and synthesized.Based on the Cp,the phase transfer of chiral ionic liquids(CILs)in water/alcohol biphasic system was realized.Then,using the CILs as stabilizers,the chiral Pt nanocatalysts with thermoregulated phase transfer property were prepared and the thermoregulated phase transfer chiral Pt nanocatalytic system was constructed.The characteristics of such catalysis system are depicted as follows:before reaction,the system consists of lower aqueous phase containing CIL stabilized chiral Pt nanocatalyst and the upper alcohol phase containing substrates.When the temperature rises above the Cp,the chiral Pt nanocatalyst in the aqueous phase will transfer into the upper alcohol phase.And the reaction takes place homogeneously.After reaction,when the temperature drops below the Cp,the chiral Pt nanocatalyst will return to the aqueous phase.Thus,by simple separation the chiral Pt nanocatalyst can be separated and recycled.The above-mentioned chiral ionic liquids stabilized chiral Pt nanocatalysts were applied to the asymmetric hydrogenation ofα-ketoesters.When CILTPT-1/Pt was used as the catalyst and methyl benzoylformate(MBF)was used as the template substrate,>99%conversion and ee value were obtained under the optimized conditions.After simple phase separation,the chiral CILTPT-1/Pt nanocatalyst could be recycled four times.The conversion and ee remained unchanged(>99%).Considering that most studies on catalyst phase transfer involving ionic liquids are still limited to the use of fluorinated anions,which are costly and environmentally unfriendly.Therefore,the fluorine-free chiral ionic liquid CILTPT-MS[CH3(OCH2CH2)16CD]+[CH3SO3]-(CD=cinchonidine)was investigated in this study.It was confirmed that the chiral ionic liquid CILTPT-MS has a“cloud point”property.The thermoregulated phase transfer of CILTPT-MS stabilized chiral Pt nanocatalyst in water/alcohol two-phase system was realized and a fluorine-free thermoregulated phase transfer chiral Pt nanocatalytic system was constructed.The above-mentioned fluorine-free thermoregulated phase transfer chiral Pt nanocatalytic system was applied to the asymmetric hydrogenation ofα-ketoesters.Under the optimized reaction conditions,the conversion of MBF and the ee values of the product were>99%.In the recycling experiments,the chiral Pt nanocatalyst can be recycled for 4 times without compromising the enantioselectivity.Thus,in this fluorine-free thermoregulated phase transfer chiral Pt nanocatalytic system,not only>99%conversion and ee were obtained,but also the easy separation and recycling of the chiral Pt nanocatalyst were achieved. |