Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA.
Science. 2010 Feb 19;327(5968):986-90. doi: 10.1126/science.1182826.
Cationic organic intermediates participate in a wide variety of useful synthetic transformations, but their high reactivity can render selectivity in competing pathways difficult to control. Here, we describe a strategy for inducing enantioselectivity in reactions of protio-iminium ions, wherein a chiral catalyst interacts with the highly reactive intermediate through a network of noncovalent interactions. This interaction leads to an attenuation of the reactivity of the iminium ion and allows high enantioselectivity in cycloadditions with electron-rich alkenes (the Povarov reaction). A detailed experimental and computational analysis of this catalyst system has revealed the precise nature of the catalyst-substrate interactions and the likely basis for enantioinduction.
阳离子有机中间体参与了各种各样的有用的合成转化，但它们的高反应性使得难以控制竞争途径中的选择性。在这里，我们描述了一种在质子化亚胺离子反应中诱导对映选择性的策略，其中手性催化剂通过非共价相互作用网络与高反应性中间体相互作用。这种相互作用导致亚胺离子的反应性降低，并允许在与富电子烯烃的环加成反应中具有高对映选择性（Povarov 反应）。对该催化剂体系的详细实验和计算分析揭示了催化剂-底物相互作用的精确性质和对映诱导的可能基础。
