Helical Oligourea Foldamers as Powerful Hydrogen Bonding Catalysts for Enantioselective C-C Bond-Forming Reactions
Helical Oligourea Foldamers as Powerful Hydrogen Bonding Catalysts for Enantioselective C-C Bond-Forming Reactions
复制标题
DOI：
10.1021/jacs.7b05802
复制
发表时间：
2017-09-13
影响因子：
15
通讯作者：
Guichard, Gilles
中科院分区：
文献类型：
--
作者：
Becart, Diane;Diemer, Vincent;Guichard, Gilles
对映体选择性转化的无金属催化剂的开发已经取得了实质性进展，然而在低催化剂负载下有效的有机催化剂的发现仍然是一个主要挑战。在这里，我们报告了一种新的协同催化剂组合系统组成的肽启发的手性螺旋（硫）脲低聚物80和一个简单的叔胺，能够促进可烯醇化的羰基化合物和硝基烯烃之间的迈克尔反应，具有优异的对映选择性在非常低的（1/10000）手性催化剂/底物摩尔比。除了与螺旋折叠密切相关的高选择性之外，我们在这里报告的系统也非常适合优化，因为它的每个组件都可以单独微调以增加反应速率和/或选择性。折叠体二级结构的可预测性与对一级序列的高水平控制相结合，导致系统具有未来催化剂设计的显著潜力。
Substantial progress has been made toward the development of metal-free catalysts of enantioselective transformations, yet the discovery of organic catalysts effective at low catalyst loadings remains a major challenge. Here we report a novel synergistic catalyst combination system consisting of a peptide-inspired chiral helical (thio)urea oligomer 80 and a simple tertiary amine that is able to promote the Michael reaction between enolizable carbonyl compounds and nitroolefins with excellent enantioselectivities at exceptionally low (1/10000) chiral catalyst/substrate molar ratios. In addition to high selectivity, which correlates strongly with helix folding, the system we report here is also highly amenable to optimization, as each of its components can be fine-tuned separately to increase reaction rates and/or selectivities. The predictability of the foldamer secondary structure coupled to the high level of control over the primary sequence results in a system with significant potential for future catalyst design.