Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
Center for Catalytic Hydrocarbon Functionalizations, Institute for Basic Science (IBS), Daejeon 34141, Korea.
J Am Chem Soc. 2020 Jul 15;142(28):12420-12429. doi: 10.1021/jacs.0c05025. Epub 2020 Jul 2.
By utilizing an underexplored reactivity mode of -aminopyridinium ylides, we developed the visible-light-induced -selective aminopyridylation of alkenes via radical-mediated 1,3-dipolar cycloaddition. The photocatalyzed single-electron oxidation of -aminopyridinium ylides generates the corresponding radical cations that enable previously inaccessible 1,3-cycloaddition with a broader range of alkene substrates. The resulting cycloaddition adducts rapidly undergo subsequent homolytic cleavage of the N-N bond, conferring a substantial thermodynamic driving force to yield various β-aminoethylpyridines. Remarkably, amino and pyridyl groups can be installed into both activated and unactivated alkenes with modular control of -selectivity and 1,2-diastereoselectivity under metal-free and mild conditions. Combined experimental and computational studies are conducted to clarify the detailed reaction mechanism and the origins of site selectivity and diastereoselectivity.
利用 - 氨基吡啶叶立德未被充分探索的反应模式，我们通过自由基介导的 1,3-偶极环加成反应，开发了可见光诱导的 - 选择性烯基氨基吡啶化反应。- 氨基吡啶叶立德的光催化单电子氧化生成相应的自由基阳离子，使以前无法进行的与更广泛的烯烃底物的 1,3-环加成反应成为可能。所得的环加成加合物迅速经历 N-N 键的后续均裂裂解，为生成各种 β- 氨基乙基吡啶提供了很大的热力学驱动力。值得注意的是，在无金属和温和条件下，通过模块控制 - 选择性和 1,2-非对映选择性，可以将氨基和吡啶基同时引入到活化和非活化的烯烃中。进行了组合的实验和计算研究，以阐明详细的反应机制以及位点选择性和非对映选择性的起源。
