Department of Chemistry and Chemical Biology Baker Laboratory, Cornell University Ithaca, New York 14853-1301, United States.
J Am Chem Soc. 2018 Feb 28;140(8):3077-3090. doi: 10.1021/jacs.7b13776. Epub 2018 Feb 19.
Building on structural and mechanistic studies of lithiated enolates derived from acylated oxazolidinones (Evans enolates) and chiral lithiated amino alkoxides, we found that amino alkoxides amplify the enantioselectivity of aldol additions. The pairing of enantiomeric series affords matched and mismatched stereoselectivities. The structures of mixed tetramers showing 2:2 and 3:1 (alkoxide-rich) stoichiometries are determined spectroscopically. Rate and computational studies provide a viable mechanistic and stereochemical model based on the direct reaction of the 3:1 mixed tetramers, but they raise unanswered questions for the 2:2 mixed aggregates.
基于酰化恶唑烷酮（Evans 烯醇盐）衍生的锂化烯醇化物和手性锂化氨基烷氧基化物的结构和机制研究，我们发现氨基烷氧基化物可以提高 aldol 添加的对映选择性。对映体系列的配对提供了匹配和不匹配的立体选择性。通过光谱学确定了显示 2:2 和 3:1（烷氧基丰富）化学计量比的混合四聚体的结构。速率和计算研究提供了一个可行的基于直接反应的 3:1 混合四聚体的机制和立体化学模型，但对于 2:2 混合聚集体，它们提出了一些未解决的问题。
