Stereocontrolled synthesis of carbocyclic compounds with a quaternary carbon atom based on SN2′ alkylation of γ,δ-epoxy-α,β-unsaturated ketones
作者:Fumihiko Yoshimura、Ayano Kowata、Keiji Tanino
DOI:10.1039/c2ob25719j
日期:——
We developed a new method for stereoselective construction of an all-carbon quaternary stereogenic center on a carbocyclic ring based on regio- and stereoselective SN2′ alkylation reactions of γ,δ-epoxy-α,β-unsaturated cyclic ketones. Treatment of the ketones, which were readily prepared in enantiomerically pure form by means of aldol condensations between 3-ethoxy-2-cycloalkenones and α,β-epoxy aldehydes
我们开发了一种新方法,用于基于γ,δ-环氧-α,β-不饱和环酮的区域和立体选择性S N 2'烷基化反应,在碳环上立体选择性构建全碳四元立体中心。用R 2 Zn-CuCN试剂处理酮,很容易以对映体纯的形式通过3-乙氧基-2-环烯酮和α,β-环氧醛之间的醛醇缩合制备酮,得到抗-S N 2'产物。立体选择性地。相反,相应的syn -S N通过对相同的γ,δ-环氧-α,β-不饱和环状酮进行两步转化来立体选择性地获得2'产物:(1)通过用MgCl 2处理将环氧部分转化为氯醇,以及(2)随后的S用R 2 Zn-CuCN试剂对氯醇进行N 2'取代。这些具有手性反式烯丙基醇部分的取代产物是复杂分子的有前途的前体。例如,一种取代产物的Eschenmoser-Claisen重排导致具有连续的四级和三级立体生成中心的酮酰胺的立体选择性形成。