Asymmetric induction in the thio-claisen rearrangement. Creation of three contiguous stereogenic centres from α-hydroxy ketene dithioacetals
作者:Pierre Beslin、Stéphane Perrio
DOI:10.1016/s0040-4020(01)92192-1
日期:1992.1
selective cis deprotonation. These dithioacetals underwent a rapid and highly diastereoselective thio-Claisen rearrangement at an ambient temperature. Syn-syn α-allyl β-hydroxy γ-methyl dithioesters were mainly formed. The syn-syn/anti-syn ratios ranged from 85 : 15 to 99 : 1. The selectivity observed originated from asymmetric induction with a noteworthy stereoelectronic effect of the hydroxyl group
用两当量的LDA使合成的β-羟基γ-甲基二硫代酯去质子化。所得二价阴离子的后续S-烷基化产生α-羟基S-烯丙基烯酮二硫缩醛。观察到一个单一的异构体,由选择性的顺式去质子化产生。这些二硫缩醛在环境温度下经历了快速且高度非对映选择性的硫代-克莱森重排。主要形成了顺式-顺式α-烯丙基β-羟基γ-甲基二硫酯。syn-syn / anti-syn比率范围为85:15至99:1。观察到的选择性源自不对称诱导,并带有明显的羟基立体电子效应。使用先前报道的13通过分光镜方法分配配置C NMR规则,然后通过顺-顺非对映选择性醛醇缩合反应确认。这种新颖且有效的方法用于创建具有三个连续的立体异构中心的框架,涉及两个非对映选择性步骤:硫代-克莱森重排引起的醛醇缩合反应。