Asymmetric Nitrocyclopropanation of α-Substituted α,β-Enals Catalyzed by Diphenylprolinol Silyl Ether for the Construction of All-Carbon Quaternary Stereogenic Centers
作者:Yujiro Hayashi、Tatsuya Yamazaki、Yuki Nakanishi、Tsuyoshi Ono、Tohru Taniguchi、Kenji Monde、Tadafumi Uchimaru
DOI:10.1002/ejoc.201500838
日期:2015.9
The diphenylprolinol silyl ether mediated asymmetric nitrocyclopropanation of α-substituted α,β-unsaturated aldehydes with bromonitromethane, followed by base-promoted isomerization was found to afford trans-nitrocyclopropanecarbaldehydes with all-carbon quaternary stereogenic centers with excellent diastereo- and enantioselectivities. DFT calculations indicated that the s-trans conformer of the iminium
发现二苯基脯氨醇甲硅烷基醚介导的 α-取代的 α,β-不饱和醛与溴硝基甲烷的不对称硝基环丙烷化,然后是碱促进的异构化,可提供具有全碳四元立体中心的反式硝基环丙烷甲醛,具有优异的非对映选择性和对映选择性。DFT 计算表明亚胺离子中间体的 s-反式构象异构体比 s-顺式构象异构体更稳定。此外,计算出溴硝基甲烷阴离子对亚胺离子中间体的亲核攻击优先发生在吡咯烷亚胺中间体的大取代基的相反侧。