金鸡纳碱衍生物修饰的负载铱催化剂催化芳香酮不对称加氢

Asymmetric Hydrogenation of Aromatic Ketones Catalyzed by Cinchona-Modified Ir/SiO_2

以金鸡纳碱衍生物作为手性修饰剂,研究了三苯基膦稳定的Ir/SiO2催化剂催化芳香酮多相不对称加氢.通过电感耦合等离子体原子发射发谱(ICP-AES)、高分辨透射电镜(HRTEM)、X射线光电子能谱(XPS)、Brunauer-Emmett-Teller(BET)比表面积测试等固体表面分析手段对负载铱催化体系进行了表征;利用红外(IR)光谱、固体核磁共振(NMR)等分析手段初步表征了负载铱多相催化体系中手性修饰剂-金属-稳定剂在载体上的相互作用;利用'均相与多相催化体系的对比'、'催化剂稳定性实验'、'汞中毒实验'等方法阐明了手性修饰的负载铱催化体系是多相催化体系.还考察了稳定剂种类、修饰剂种类、金属负载量、溶剂、碱添加剂种类等因素对不对称加氢反应的影响.结果表明,金鸡纳碱衍生物对Ir/SiO2催化剂具有较好的修饰作用,在优化反应条件下苯乙酮及其衍生物加氢反应的对映选择性为52%-96%,4-乙酰基吡啶、2-乙酰基噻吩及2-乙酰基呋喃加氢反应的对映选择性可分别达到74%、75%及63%.

The asymmetric hydrogenation of aromatic ketones catalyzed by cinchona- and triphenylphosphine （tpp）-modified Ir/SiO2 was studied. The heterogeneous enantioselective hydrogenation of heterocyclic ketones using a supported iridium catalyst was also investigated. Different analytical techniques, including inductively coupled plasma-atomic emission spectroscopy （ICP-AES）, high resolution transmission electron microscopy （HRTEM）, X-ray photoelectron spectroscopy （XPS）, the Brunauer- Emmett-Teller （BET） method, infrared （IR） spectroscopy, 3,p solid state nuclear magnetic resonance （NMR） spectroscopy, homogeneous- heterogeneous comparison experiment, conventional filtering test, and mercury poisoning experiment, were used to characterize the catalytic system. HRTEM, XPS, and the BET method cleady characterized the catalytic system. IR and 31p solid state NMR spectra provided useful information about the interactions between modifier, metal, and stabilizer. The homogeneous-heterogeneous comparison experiment, conventional filtering test, and mercury poisoning experiment cleady showed the differences between supported, and homogeneous catalysts. In addition, the effects of different stabilizers, modifiers, iridium content, solvents, and base additives on the asymmetric hydrogenation of aromatic ketones were investigated in detail. The results showed that cinchona alkaloids positively modified the Ir/ SiO2 catalyst. Under the optimum conditions, the hydrogenation enantioselectivities of acetophenone and its derivatives were 52%-96%. The enantioselectivities of the hydrogenation products of 4-acetopyridine, 2-acetothiophene, and 2-acetofuran reached 74%, 75%, and 63%, respectively.