Copolymer-supported heterogeneous organocatalyst for asymmetric aldol addition in aqueous medium
作者:Jinqing Zhou、Jinwei Wan、Xuebing Ma、Wei Wang
DOI:10.1039/c2ob25106j
日期:——
conditions. Compared with cyclohexanone, cyclopentanone and acetone showed the less desired enantioselectivities in the same aldol reactions. At the end of the aldol reaction, the copolymer-supported organocatalyst 1a was readily recovered in 95–98% yield from reaction mixture by simple filtration using an organic membrane. Even in the fifth run, there was no significant loss in catalytic activity and stereocontrol
在当前的研究中,提出了一种方便和简单的方法,以AIBN为自由基引发剂,将9-氨基-9-脱氧-表位-辛可宁有机催化剂与丙烯腈共聚,以21-81%的产率合成新型负载型多相有机催化剂。。共聚物1a–d的化学组成(x / y)和重均分子量分别通过1 H NMR和GPC分析确定。它们的多孔和层状结构以及表面形貌通过氮吸附-解吸,XRD和TEM表征。在水中对硝基苯甲醛与对硝基苯甲醛的不对称醛醇加成反应中,所有负载的有机催化剂1a–d可提供出色的分离产率(90.2–94.7%)和立体选择性(96.8–97.8%ee抗,抗/ syn = 91/9)。在优化的条件下,在水中作为唯一的溶剂可获得最高的催化性能(96%的收率,抗/ syn = 90/10和99%ee抗)。与环己酮相比,环戊酮和丙酮在相同的羟醛反应中显示出较低的对映选择性。在醛醇缩合反应结束时,共聚物负载的有机催化剂1a通过使用有机膜的简单过滤,