[reaction: see text] High stereoselective beta-elimination in 2,3-epoxyesters 1 was achieved using samarium diiodide, yielding alpha,beta-unsaturated esters 2, in which the C=C bond is di-, tri- or tetrasubstituted. The starting compounds 1 are easily prepared by reaction of the corresponding lithium enolates of alpha-chloroesters with aldehydes or ketones at -78 degrees C. The influence of the reaction
[反应:见正文]使用二
碘化sa在2,3-环氧酯1中实现高立体选择性β-消除,生成α,β-不饱和酯2,其中C = C键被二,三或四取代。通过使相应的α-
氯代酯的烯醇
锂与醛或酮在-78℃下反应,可以轻松地制备起始化合物1。反应条件和起始化合物的结构对β-消除反应立体选择性的影响也进行了讨论。