Cyclopropanation Reactions of Enones with Lithiated Sulfoximines: Application to the Asymmetric Synthesis of Chiral Cyclopropanes
作者:Stephen G. Pyne、Zemin Dong、Brian W. Skelton、Allan H. White
DOI:10.1021/jo962216i
日期:1997.4.1
kinetically controlled conditions. At rt the initially formed anionic Michael adducts undergo intramolecular displacement of the sulfonimidoyl group, with inversion of stereochemistry at the carbon bearing the nucleofuge, to give cyclopropanes. Lithiated sulfoximines derived from S-alkyl sulfoximines give mixtures of 1,2- and 1,4-adducts with enones under kinetically controlled conditions. However, at rt
在动力学控制的条件下,稳定的锂化亚砜亚砜2和9与非环烯酮进行高度非对映选择性Michael反应。在室温下,最初形成的阴离子迈克尔加合物经历了磺酰亚胺基的分子内置换,同时带有核试剂的碳上的立体化学转化,从而生成环丙烷。在动力学控制的条件下,衍生自S-烷基亚磺酰亚胺的锂化亚磺酰亚胺产生1,2-和1,4-加合物与烯酮的混合物。但是,在室温下,1,2-加合物与其相应的1,4-加合物处于平衡状态。1,4-加合物以高度非对映选择性的方式形成,并以良好或优异的收率迅速转化为非对映体纯的环丙烷。这些亚砜亚胺的旋光形式可得到高对映体纯度的环丙烷。