Structural Effects on the Catalytic, Emulsifying, and Recycling Properties of Chiral Amphiphilic Dendritic Organocatalysts
作者:Chui-Man Lo、Hak-Fun Chow
DOI:10.1021/jo9006128
日期:2009.8.7
was also found that higher product yields and enantioselectivities were obtained in the aldol reactions when the aromatic aldehyde contains an electron-withdrawing substituent. The catalysts could be recycled and reused five times without significant drop in product yields and enantioselectivities. In addition, cross product contamination was not found when the recovered G3 catalyst was subsequently
制备了三个系列的手性两亲性G1-G3树状有机催化剂,它们包含旋光性脯氨酸衍生的核和一个或两个非极性烃类树突。这些树状有机催化剂被用于水包油乳液的不对称醛醇和硝基-迈克尔加成反应中,以揭示树突尺寸和支化度对催化性能的影响。引入较大的疏水树突具有以下优点:促进水中乳液的形成,提高反应对映选择性,降低催化剂负载量(至1mol%),并促进反应后催化剂的回收。通常,较大的树枝状分子由于其增加的位阻作用而趋于降低催化剂的反应性。但是,在某些G1和G2树突状有机催化剂中发现了一些惊人的发现,其中,树枝状分子的空间体积和分支的增加导致更好的催化剂反应性。还发现当芳族醛包含吸电子取代基时,在醛醇缩合反应中获得更高的产物产率和对映选择性。催化剂可以循环使用五次,而产物收率和对映选择性没有明显下降。另外,当回收的G3催化剂随后用于涉及不同底物的另一反应中时,未发现交叉产物污染。还发现当芳族醛包含吸电子取代基时,