Highly active oligomeric Co(salen) catalysts for the asymmetric synthesis of α-aryloxy or α-alkoxy alcohols via kinetic resolution of terminal epoxides
作者:Xunjin Zhu、Krishnan Venkatasubbaiah、Marcus Weck、Christopher W. Jones
DOI:10.1016/j.molcata.2010.06.015
日期:2010.8.17
alcohols. The catalyst is compared to other dimeric, oligomeric and monomeric Co(salen) complexes including a pimelate-linked macrocyclic Co(salen) catalyst and a dimeric Co(salen) catalyst referred to as a bisalen. The catalysts that contain multiple Co(salen) units within a single molecular framework allow for substantial decreases in catalyst loading compared with the monomeric catalyst. The cyclooctene-based
在最活跃的末端环氧化物水解动力学拆分(HKR)催化剂中,通过Salen官能化环辛烯单体的扩环易位低聚反应制备的Co(salen)大环混合物被用作环的催化剂,使用脂族醇或酚作为亲核试剂打开环氧化物,导致光学活性的α-芳氧基醇或α-烷氧基醇直接合成。将该催化剂与其他二聚,低聚和单体的Co(salen)配合物进行比较,其中包括庚二酸酯连接的大环Co(salen)催化剂和称为Bialen的二聚Co(salen)催化剂。与单体催化剂相比,在单个分子框架内包含多个Co(salen)单元的催化剂可大大降低催化剂的负载量。基于环辛烯的Co(salen)大环催化剂在以酚为亲核剂的末端环氧化物的开环中具有良好的活性和对映选择性,相对于许多文献催化剂而言,其周转频率提高了。环辛烯基Co(salen)大环催化剂和双芳烃催化剂在(±)1,2-环氧己烷与甲醇的不对称开环中表现出最强的活性,优于其他测试的催化剂。Co(