Key Laboratory of Synthetic and Natural Functional Molecule of the Ministry of Education, College of Chemistry & Materials Science, Northwest University, Xi'an 710127, P. R. China.
J Am Chem Soc. 2020 Apr 8;142(14):6698-6707. doi: 10.1021/jacs.0c00403. Epub 2020 Mar 27.
Conventional approaches on using hydroxylamine derivatives as single nitrogen sources, for the construction of -membered ( > 3) N-heterocycles, rely upon two chemical operations by involving sequential nucleophilic and electrophilic C-N bond formations. Here, we report a highly efficient cascade of alkyne insertion/C-H activation/amination for the rapid preparation of a myriad of tricyclic indoles, in a single-step transformation, by using bifunctional secondary hydroxylamines. It is noteworthy that judicious selection of applicable amino agents, for enabling the prior oxidative addition of aryl iodide to initial Pd(0) species and subsequent two C-N bonds formation, was the key to the success of this reaction. Control experiments indicated that a five-membered palladacyclic intermediate played a crucial role in promoting the final aminative ring closure.
常规方法是使用羟胺衍生物作为单一氮源，构建五元（> 3）N-杂环，这需要通过涉及顺序亲核和亲电 C-N 键形成的两个化学操作。在这里，我们报告了炔烃插入/C-H 活化/胺化的高效级联反应，通过使用双功能仲羟胺，可以在一步转化中快速制备多种三环吲哚。值得注意的是，明智地选择适用的氨基试剂，以使芳基碘化物能够先进行氧化加成到初始 Pd(0)物种，然后再进行两个 C-N 键的形成，这是反应成功的关键。对照实验表明，五元钯环中间体在促进最终的胺化环闭反应中起着关键作用。
