手性金属纳米粒子的温控相分离催化体系及应用

With the aim to realize the thermoregulated phase-separable catalysis towards chiral metal nanoparticle catalysts, novel chiral ionic liquids with the property of critical solution temperature (CST) will be synthesized and used as stabilizers for preparation of chiral metal nanoparticles. The as-prepared chiral metal nanoparticle catalyst exhibits very unique solubility in organic solvent depending on the temperature. Namely, the chiral metal nanoparticle catalyst dissolved in the lower chiral ionic liquid phase is immiscible with the upper organic solvent phase at room temperature (lower than CST), but becomes homogeneous when the temperature is increased to a certain point (higher than CST). Consequently, the reaction proceeds virtually in a homogeneous system under heating, and upon cooling to room temperature (lower than CST), the whole system separates into a biphasic system composed of ionic liquid phase containing chiral metal nanoparticle catalyst and organic phase containing the products. Such a novel process provides both the advantages of classic monophase and biphase system, i.e., highly catalytic efficiency and good recyclability, and will be used in the asymmetric hydrogenations of aromatic ketones and α-keto esters. More importantly, the method will provide a novel approach for easy recovery and efficient reuse of chiral metal nanoparticle catalysts,especially for noble metal nanoparticle catalysts.

设计、合成具有临界溶解温度(CST）特性的手性离子液体，并将其用作稳定剂制备手性金属纳米粒子催化剂，以期实现手性金属纳米粒子催化剂的温控相分离催化过程。即这类在室温（低于CST）时溶于下层手性离子液体相的金属纳米粒子催化剂可在升高温度（高于CST）时与溶有反应底物的上层有机溶剂混溶，均相反应。反应结束冷至室温(低于CST)后，溶有手性金属纳米粒子催化剂的离子液体则与上层溶有产物的有机溶剂分为两相，手性金属纳米粒子催化剂经简单分相即可实现与产物的分离及循环使用。本申请以芳酮和α-酮酸酯的不对称催化氢化反应为探针，考察其催化活性、对映选择性及分离回收效果，创新一种手性金属纳米粒子催化剂易于分离回收及循环使用的新途径。

为解决手性金属（尤其是贵金属）纳米催化剂研究中手性试剂以及贵金属纳米催化剂分离回收和循环使用的难题，本项目设计、合成了一系列具有临界溶解温度（CST) 特性的手性离子液体，以该手性离子液体为稳定剂通过化学还原法制备了Pt、Ir、Ru、Rh和Pd等手性金属纳米催化剂，并实现了上述手性金属纳米催化剂的温控相分离催化过程。即这类在室温（低于CST)时溶于下层手性离子液体相的手性金属纳米催化剂可在升高温度（高于CST)时与溶有反应底物的上层有机溶剂混溶，均相反应。反应结束冷至室温（低于CST)后，溶有手性金属纳米催化剂的离子液体则与上层溶有产物的有机溶剂分为两相，手性金属纳米催化剂经简单分相即可实现与产物的分离及循环使用。上述创建的含手性金属纳米催化剂的温控相分离催化体系已在α-酮酸酯的不对称氢化反应中成功应用，创新了一种手性金属纳米催化剂易于分离回收及循环使用的新途径。