Zhang Haidong, Zou Yu, Wang Yi-Meng, Shen Yu, Zheng Xuxu
Chongqing Key laboratory of catalysis science and technology Engineering research centre of waste oil recovery technology and equipment of Chinese ministry of education Chongqing Technology and Business University, Chongqing 400067 (P. R. China), Fax: (+86) 23-62768317.
Chemistry. 2014 Jun 16;20(25):7830-41. doi: 10.1002/chem.201402136. Epub 2014 May 23.
Immobilised Mn(salen) catalysts with two different linkages were studied in the asymmetric epoxidation of cis/trans-β-methylstyrene using NaClO as oxidant. The immobilised Mn(salen) complexes inside nanopores can lead to different catalytic behaviour compared with that of homogeneous Jacobsen catalyst. The rigidity of the linkage was found to be a key factor affecting the catalytic performance of immobilised catalysts. The immobilised catalyst with a rigid linkage exhibited comparable chemical selectivity, enantioselectivity and cis/trans ratio of product formation to that obtained with homogeneous Jacobsen catalysts. In contrast, the immobilised catalyst with a flexible linkage gave remarkably lower chemical selectivity, enantioselectivity and inverted cis/trans ratio compared with the results obtained with the homogeneous Jacobsen catalyst and the immobilised catalyst with rigid linkage. Thus, for immobilised Mn(salen) catalysts, a rigid linkage connecting active centres to the support is essential to obtain activity and enantioselectivity as high as those obtained in homogeneous systems.
使用次氯酸钠作为氧化剂，研究了具有两种不同连接方式的固定化Mn(salen)催化剂在顺式/反式-β-甲基苯乙烯不对称环氧化反应中的性能。与均相雅各布森催化剂相比，纳米孔内的固定化Mn(salen)配合物可导致不同的催化行为。发现连接键的刚性是影响固定化催化剂催化性能的关键因素。具有刚性连接键的固定化催化剂在化学选择性、对映选择性和产物形成的顺式/反式比例方面与均相雅各布森催化剂相当。相比之下，与均相雅各布森催化剂和具有刚性连接键的固定化催化剂的结果相比，具有柔性连接键的固定化催化剂的化学选择性、对映选择性显著降低，且顺式/反式比例反转。因此，对于固定化Mn(salen)催化剂，将活性中心连接到载体的刚性连接键对于获得与均相体系相当的活性和对映选择性至关重要。
