γ-Hydroxy-α,β-alkenenitriles: Chelation-Controlled Conjugate Additions<sup>1</sup>
作者:Fraser F. Fleming、Qunzhao Wang、Zhiyu Zhang、Omar W. Steward
DOI:10.1021/jo0258150
日期:2002.8.1
Grignard and organolithium reagents to gamma-hydroxy-alpha,beta-alkenenitriles promotes efficient conjugate additions to what are otherwise recalcitrant Michael acceptors. Sequential deprotonation and addition of a modest excess of a second Grignard reagent allows effective conjugate delivery of alkyl groups to cyclic and acyclic alkenenitriles. Mechanistically, conjugate additions proceed through alkylmagnesium
暂时将格氏试剂和有机锂试剂锚定在γ-羟基-α,β-烯腈上,可促进将有效的共轭物添加到本来难以顽固的迈克尔受体上。连续的去质子化和适度过量的第二种格氏试剂的加入允许将烷基基团有效地共轭递送至环状和非环状的链烯腈。从机理上讲,共轭加成反应是通过烷基镁醇盐配合物进行的,除了取代度更高的烯腈以外,所有其他化合物都需要从反应性较高的配合物中进行烷基转移。综合地,螯合控制的共轭物的添加迅速且立体选择性地组装了取代的腈,在一次合成操作中最多可安装两个新的立体中心。