α,β-不饱和酸多相不对称氢化反应中的钯粒径和载体酸性效应(英文)  

Enantioselective Hydrogenation of α,β-Unsaturated Carboxylic Acids:Effects of Palladium Particle Size and Support Acidic Property

作　　者：陈春辉[1] 展恩胜[1] 李勇[1] 申文杰[1] 

机构地区：[1]中国科学院大连化学物理研究所催化基础国家重点实验室,大连116023

出　　处：《化学学报》2013年第11期1505-1510,共6页Acta Chimica Sinica

基　　金：Project supported by the National Natural Science Foundation of China(No.20921092)~~

摘　　要：使用胶体沉积法制备了具有不同钯粒径、不同氧化物载体的负载型钯催化剂,系统地研究了α,β-不饱和酸的多相不对称氢化反应中的钯粒径和载体效应.结果表明钯粒径仅影响反应的活性而与对映体选择性无关.这是由于在较小的钯粒子上存在较多的边,角等区域,而这些区域具有较高的双键加氢活性,因而在较小的粒子上具有较高的氢化反应速率但是粒径的变化并没有改变手性修饰剂与反应中间体的吸附模式.载体的酸性对反应的活性和对映体选择性都有促进作用,说明酸性载体有利于反应中间体的吸附.Effects of Pd particle size and support acidity on enantioselective hydrogenation of a,fl-unsaturated carboxylic acids were systematically studied using Pd nanoparticles with different size immobilized on various oxides. Small Pd parti- cles showed higher activity in the hydrogenation of （E）-2-methyl-2-pentenoic acid due to the larger fraction of edge sites which were more active in olefin hydrogenation; but they did not change the reaction mechanism and/or the adsorption mode of reaction intermediates. Similar correlations in the hydrogenation of （E）-2-methyl-2-butenoic acid and 2-acetamidoacrylic acid further confirmed that the size of Pd particles only mediated the activity but did not alter the enantioselectivity. On the other hand, the activity and the enantioselectivity were strongly dependent on the acidity of the support. The TOF and the ee value followed the order TiO2 〉 y-A1203 〉 SiO2 〉 CeO2, suggesting that the acidic support favored the adsorption of the reac- tion intermediates.

关 键 词：α β-不饱和酸 不对称氢化 钯粒径 载体效应 

分 类 号：O621.25[理学—有机化学]