作者:Cesare Gennari、M. Grazia Beretta、Anna Bernardi、Giorgio Moro、Carlo Scolastico、Roberto Todeschini
DOI:10.1016/s0040-4020(01)87496-2
日期:1986.1
silylketene acetal additions to aldehydes are stereoconvergent and give high anti-syn ratios and good chemical yields. An acyclic transition state model was hypothesized in order to account for the observed selectivity. Theoretical methods (MNDO) were used to evaluate the ground-state conformations of thioester silylketene acetals and to model the acyclic transition states. Lewis acid mediated additions
BF 3 -OEt 2介导的硫酯甲硅烷基乙烯酮缩醛在醛类中的加成反应是立体收敛的,并具有较高的反合成比和良好的化学收率。为了解释观察到的选择性,假设了一个无环过渡态模型。理论方法(MNDO)用于评估硫酯甲硅烷基乙烯酮缩醛的基态构象,并模拟无环过渡态。路易斯酸介导的硫代酸酯甲硅烷基乙烯酮缩醛向2-苯基丙醛(BF 3 -OEt 2),O-苄基乳酸醛(SnCl 4),2,3-0,O-二苄基甘油醛(SnCl 4)和3-的加成反应苄氧基-2-甲基丙醛(TiCl 4)被发现具有高度非对映体选择性,因此可以建立三个连续的立体中心。对于α-,β-或α,β-烷氧基醛,相对立体选择(螯合)可有效控制内部立体选择。使用分子力学(MM2)研究了手性醛的基态构象。