温控Noyori配体的合成及在苯乙酮不对称氢转移反应中的应用

设计并合成了一种新型的聚乙二醇单甲醚(MPEG)修饰的温控Noyori配体.将其与[RuCl2.(p-cymene)]2络合形成的催化剂用于水/环己烷两相体系中苯乙酮不对称氢转移反应.以甲酸钠为氢源,考察了反应温度、时间、甲酸钠用量、底物与催化剂摩尔比以及溶剂用量等因素对催化反应的影响.结果表明,反应体系中含催化剂的水相具有浊点,并且催化剂显示出良好的不对称催化性能,在甲酸钠/苯乙酮/催化剂的摩尔比为300:100:1、环己烷/水体积比1:1及30℃的反应条件下反应6h,苯乙酮的转化率为99.7%,产物α-苯乙醇的对映选择性(e.e.)为93.9%.催化剂相易与产物相分离并与直接循环使用,循环使用的催化剂活性明显下降,但产物对映选择性仍保持不变.

Synthesis of Thermoregulate Noyory Ligand and Its Application In Asymmtcic Transfer Hydrogenation of Acetophenone

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.