Dual Activation in Asymmetric Allylsilane Addition to Chiral <i>N</i>-Acylhydrazones: Method Development, Mechanistic Studies, and Elaboration of Homoallylic Amine Adducts
作者:Gregory K. Friestad、Chandra Sekhar Korapala、Hui Ding
DOI:10.1021/jo052037d
日期:2006.1.1
CN bonds. In the presence of indium(III) trifluoromethanesulfonate [In(OTf)3], N-acylhydrazones undergo highly diastereoselective fluoride-initiated additions of allylsilanes (aza-Sakurai reaction). Mechanistic studies including control experiments and comparisons with allyltributylstannane, allylmagnesium bromide, and allylindium species implicate a dual activation mechanism involving addition of an
衍生自可商购的4-苄基-2-恶唑烷酮的手性N-酰基hydr提供了刚性的,构象受限的模板,除了具有C N键外,还赋予了面部选择性。在三氟甲磺酸铟(III)[In(OTf)3 ]存在下,N-酰基hydr进行烯丙基硅烷的非对映选择性氟化引发的高度非对映选择性(氮杂-樱井反应)。包括对照实验在内的机理研究以及与烯丙基三丁基锡烷,烯丙基溴化镁和烯丙基锡的比较,都暗示了双重活化机制,该机制涉及将烯丙基氟硅酸盐物质添加到由In(OTf)3和手性N形成的螯合物中-酰基hydr。加合物的N-N键很容易在两步操作中裂解,以提供合成上有用的均烯丙基N-三氟乙酰胺。通过Wacker氧化和烯烃复分解对后一种化合物的进一步加工提供了功能多样的结构单元,并扩展了这种C-C键构建方法在不对称胺合成中的潜在应用。