TiO_2负载的纳米铑簇合物催化丙酮酸乙酯不对称氢化反应的研究

研究了辛可尼定作手性修饰剂修饰的负载型纳米铑簇保物催化剂（0.5% Rh/PVP-TiO_2）催化丙酮酸乙酯不对称氧化反应，在该反应中手性修饰剂辛可尼 定不仅具有对产物生成的手性诱导作用，而且对反应具有明显加速作用；在优化反 应条件后，反应的TOF和对映选择性分别可以达到58.0 min~(-1)和61.9% e.e.。

Studies on the Asymmetric Hydrogenation of Ethyl Pyruvate Catalyzed by TiO_2 Supported Rhodium Nanocluster

In the asymmetxic hydrogenation of ethyl pyruvate catalyzed by 0.5% Rh/PVP-TiO_2, the chiral modifier cinchonidine not only induces the enantioselectivity, but also accelerates the reaction rate greatly. A promotion effect of TiO_2 for the asymmetric hydrogenation is observed, when the modified rhodium nanoclusters are supported on TiO_2. The results show that TOF increase from 15.7 to 58.6 min~(-1) and e.e. values of R( + )-ethyl lactate increase from 42.2% to 60.0% in the hydrogenation of ethyl pyruvate. This suggests that TiO2 is favourable for the dispersion of Rh/PVP and its stabilization on the support surface. Under the optimum conditions: 298 K, p_(H_2) =6.0 MPa, 4. 3*10~(-3) mol/L cinchonidine in THF, ethyl pyruvate/rhodium = 942 (molar ratio), TOF and e.e. value are 58.6 min~(-1) and 61.9%, respectively.