Synthesis of Polysubstituted Imidazoles and Pyridines<i>via</i>Samarium(III) Triflate-Catalyzed [2+2+1] and [4+2] Annulations of Unactivated Aromatic Alkenes with Azides
作者:Yingchun Wang、Jiuling Li、Yan He、Yuyang Xie、Hengshan Wang、Yingming Pan
DOI:10.1002/adsc.201500584
日期:2015.10.12
Samarium(III) triflate-catalyzed [2+2+1] and [4+2] annulations have been identified for the preparation of fully substituted imidazoles and 2,3,5-trisubstituted pyridines from the readily available unactivated aromatic alkenes and azidomethyl aromatics. These reactions proceeded smoothly with one- or two-nitrogen synthons to afford a range of two types of skeletally distinct N-heterocycles in good
identified(III)三氟甲磺酸酯催化的[2 + 2 + 1]和[4 + 2]环已确定可从容易获得的未活化芳烃和叠氮甲基芳烃制备完全取代的咪唑和2,3,5-三取代的吡啶。这些反应用一个或两个氮合成子顺利进行,以高收率提供了一系列两种类型的骨架不同的N-杂环。机理研究表明,环化反应通过三氟甲磺酸sa(III)引发的1,3偶极环加成反应进行,然后发生1,2-迁移,形成烯胺作为关键中间体。密度泛函理论(DFT)计算表明1,2-H和1,2-芳基迁移的选择性取决于烯烃的结构。