Studies on the Base-Promoted Conversion of Conjugated Alkynyl Esters to α-Substituted α-Allenyl Esters
作者:Salvatore D. Lepore、Yuanjun He、Pamela Damisse
DOI:10.1021/jo0487754
日期:2004.12.1
variety of conjugated alkynyl esters to α-substituted conjugated allenyl esters (racemic) through the use of strong amide bases. Substantially improved yields over typical enolate formation conditions were observed with the use of 2 equiv of lithium diisopropylamide. Trapping studies indicate that the second equivalent of base likely leads to the dianion intermediate, which upon addition of methyl iodide
我们报告了通过使用强酰胺碱将多种共轭炔基酯转化为α-取代的共轭烯丙基酯(外消旋)的有效方法的发展。通过使用2当量的二异丙基氨基锂锂,观察到在典型的烯醇化物形成条件下产率显着提高。诱捕研究表明,第二当量的碱可能会生成二价阴离子中间体,该二价中间体在添加甲基碘,三甲基甲硅烷基氯或三丁基氯化锡时会生成α-取代的共轭烯基和β,γ-炔基共轭酯的混合物。进一步的优化表明,添加剂盐(如LiCl)主要导致烯基化产物,而使用HMPA作为助溶剂可得到β,γ-炔基去共轭的烷基化产物。碱的作用,碱的浓度,