The chemical synthesis of organic molecules involves, at its very essence, the creation of carbon–carbon bonds. In this context, the aldol reaction is among the most important synthetic methods, and a wide variety of catalytic and stereoselective versions have been reported. However, aldolizations yielding tertiary aldols, which result from the reaction of an enolate with a ketone, are challenging and only a few catalytic asymmetric Mukaiyama aldol reactions with ketones as electrophiles have been described. These methods typically require relatively high catalyst loadings, deliver substandard enantioselectivity or need special reagents or additives. We now report extremely potent catalysts that readily enable the reaction of silyl ketene acetals with a diverse set of ketones to furnish the corresponding tertiary aldol products in excellent yields and enantioselectivities. Parts per million (ppm) levels of catalyst loadings can be routinely used and provide fast and quantitative product formation in high enantiopurity. In situ spectroscopic studies and acidity measurements suggest a silylium ion based, asymmetric counteranion-directed Lewis acid catalysis mechanism.

有机分子的化学合成从本质上讲涉及碳-碳键的创建。在这种情况下，醛醇缩合反应是最重要的合成方法之一，并且已经报道了各种各样的催化形式和立体选择形式。然而，由烯醇化物与酮的反应产生的产生叔醇醛的醇醛缩合反应具有挑战性，并且仅描述了一些与酮作为亲电子体的催化不对称Mukaiyama醇醛醇缩醛反应。这些方法通常需要较高的催化剂负载量，不符合标准的对映选择性或需要特殊的试剂或添加剂。现在，我们报告了非常有效的催化剂，该催化剂可以使甲硅烷基烯酮缩醛与各种酮反应，从而以优异的收率和对映选择性提供相应的叔羟醛产物。可以按常规使用百万分之几（ppm）的催化剂负载量，并以高对映纯度提供快速定量的产物形成。原位光谱研究和酸度测量表明基于硅离子的不对称抗衡阴离子导向的路易斯酸催化机理。