Origin of the regio- and stereoselectivity of allylic substitution of organocopper reagents.
Origin of the regio- and stereoselectivity of allylic substitution of organocopper reagents.
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DOI：
10.1021/ja804682r
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发表时间：
2008-09
影响因子：
15
通讯作者：
N. Yoshikai;Song-Lin Zhang;E. Nakamura
中科院分区：
文献类型：
--
作者：
N. Yoshikai;Song-Lin Zhang;E. Nakamura
用密度泛函方法研究了异戊二酸盐MeCu(CN)Li和均戊二酸盐Me2CuLi在烯丙基取代中的区域选择性差异。MeCu(CN)Li的γ选择性是在反应的氧化加成阶段确定的，其中Me和CN基团的不同程度的反式作用决定了甲基和离去乙酸基的相对取向。结果表明，在铜原子上醋酸基团离开反式到Me基团的过渡态是有利的，从而产生了伽马选择性。同位酸盐Me2CuLi在性质上是对称的，不表现出这种区域选择性。
The origin of the contrasting regioselectivities in allylic substitution found for a heterocuprate MeCu(CN)Li and a homocuprate Me2CuLi was studied using density functional calculations. The gamma-selectivity of MeCu(CN)Li is determined at the oxidative addition stage of the reaction, where the different degree of trans effect of the Me and the CN groups dictates the relative orientation of the methyl group and the leaving acetate group. As the result, the transition state where the acetate group leaves trans to the Me group on the copper atom is favored, and the gamma-selectivity results. The homocuprate Me2CuLi is symmetrical by nature and does not show such regioselectivity.