摘要
以介孔分子筛MCM-48作载体制了以Pd(Ⅱ)-壳聚糖(CS)配合物为活性组分的手性催化剂Pd-CS/MCM-48,并利用X射线光电子能谱、X射线粉末衍射和低温N2吸附等手段研究了催化剂的结构特征.结果表明,Pd(Ⅱ)与涂覆在MCM-48表面的CS中的N原子配位生成了具有手性催化活性的Pd-CS配合物.Pd-CS/MCM-48催化剂的比表面积达527m2/g,平均孔径和孔容分别为2·1nm和0·63cm3/g.以异丙醇作氢源,将Pd-CS/MCM-48用于催化苯乙酮和4-甲基-2-戊酮的不对称氢转移反应,反应在50℃下分别进行4和8h,相应产物(R)-1-苯乙醇和(R)-4-甲基-2-戊醇的对映体过量值(ee)分别为99·0%和82·4%,底物的转化率分别为61·9%和48·7%,催化剂表现出良好的立体选择性.同时分别考察了Pd含量、反应温度、反应时间和KOH浓度等对底物转化率和产物对映选择性的影响规律.
A new chiral heterogeneous catalyst, P d-chitosan（CS） complex supported on mesoporous molecular sieve MCM-48 was prepared and characterized by X-ray photoelectron spectroscopy, X-ray diffraction, and N2 adsorption-desorption measurements. The specific surface area, average pore diameter, and pore volume of the Pd-CS/MCM-48 catalyst were 527 m^2/g, 2.1 nm, and 0.63 cm^3/g, respectively. The asymmetric transfer hydrogenation of two prochiral ketones, acetophenone and 4-methyl-2-pentanone, was catalyzed by Pd-CS/MCM- 48 using 2-propanol as the H-donor. The enantiomeric excess （ee） of （R）-l-phenylethanol reached 99.0 % with a conversion of 61.9 % after reaction for 4 h at 50 ℃, and the ee of （R）-4-methyl-2-pentanol was 82.4 % with a conversion of 48.7% after reaction for 8 h at 50 ℃. The results indicated that the Pd-CS/MCM-48 catalyst possessed a high catalytic activity and enantioselectivity for the asymmetric transfer hydrogenation of these two prochiral ketones. Moreover, the effects of Pd content, reaction temperature, reaction time, and KOH concentration on the conversion and enantioselectivity for the asymmetric transfer hydrogenation of the prochiral ketones were investigated.
出处
《催化学报》
SCIE
EI
CAS
CSCD
北大核心
2006年第6期489-494,共6页
基金
国家重大基础研究前期研究专项项目(2004CCA05900)
