A Surprising Mechanistic “Switch” in Lewis Acid Activation: A Bifunctional, Asymmetric Approach to α-Hydroxy Acid Derivatives
作者:Ciby J. Abraham、Daniel H. Paull、Tefsit Bekele、Michael T. Scerba、Travis Dudding、Thomas Lectka
DOI:10.1021/ja806818a
日期:2008.12.17
enantioenriched, alpha-hydroxylated carbonyl derivatives in excellent yield. A number of Lewis acids were screened in tandem with cinchona alkaloid derivatives; surprisingly, trans-(Ph(3)P)(2)PdCl(2) was found to afford the most dramatic increase in yield and rate of reaction. A series of Lewis acid binding motifs were explored through molecular modeling, as well as IR, UV, and NMR spectroscopy. Our observations
我们报告了一种不寻常的双功能连续杂狄尔斯-阿尔德/开环反应的详细合成和机理研究,其中手性金属络合乙烯酮烯醇化物与邻醌反应,以优异的产率提供高度对映体富集的α-羟基化羰基衍生物。与金鸡纳生物碱衍生物一起筛选了许多路易斯酸;令人惊讶的是,发现反式-(Ph(3)P)(2)PdCl(2)可显着提高产率和反应速率。通过分子建模以及红外、紫外和核磁共振光谱探索了一系列路易斯酸结合基序。我们的观察记录了一个基本的机制“转换”,即串联路易斯碱/路易斯酸活化的金属烯醇化物的形成,优先于金属配位的醌物种(如在邻醌衍生物的其他反应中观察到的)。这种新方法被应用于多种药物靶标的合成,每种药物靶标均具有高产率和对映选择性。