The Exceptional Chelating Ability of Dimethylaluminum Chloride and Methylaluminum Dichloride. The Merged Stereochemical Impact of α- and β-Stereocenters in Chelate-Controlled Carbonyl Addition Reactions with Enolsilane and Hydride Nucleophiles
作者:David A. Evans、Brett D. Allison、Michael G. Yang、Craig E. Masse
DOI:10.1021/ja011337j
日期:2001.11.1
beta-disubstituted aldehydes concludes that the syn aldehyde diastereomer possesses the arrangement of stereocenters wherein the alpha- and beta-substituents impart a reinforcing facial bias upon the aldehyde carbonyl. Aldol reactions of syn aldehydes were thus observed to proceed with uniformly excellent diastereofacial selectivity. Aldol reactions of the corresponding anti aldehydes containing opposing
介绍了在有利于螯合控制的条件下进行的非手性未取代烯醇硅烷和手性 β-羟基醛的路易斯酸促进 (Mukaiyama) 羟醛反应的立体选择性的系统研究。β-烷氧基和β-甲硅烷氧基醛的烯醇硅烷醛醇反应可以实现良好的立体控制,仅带有一个α-或β-立体中心。对α,β-二取代醛的螯合中间体的检查得出结论,syn 醛非对映异构体具有立体中心的排列,其中α-和β-取代基赋予醛羰基增强的面偏向性。因此观察到合成醛的羟醛反应以均匀优异的非对映面选择性进行。