NHC-稳定的金（I）配合物：1-(邻炔基芳基)脲的 6-endo-dig 杂环化反应的合适催化剂。

NHC-stabilized gold(I) complexes: suitable catalysts for 6-exo-dig heterocyclization of 1-(o-ethynylaryl)ureas.

机构信息

Departamento de Química Orgánica, Universidad de Valencia, 46100 Burjassot, Valencia, Spain.

出版信息

Org Lett. 2010 May 7;12(9):1900-3. doi: 10.1021/ol100595s.

PMID:20394416

Abstract

3-Substituted 1-(o-ethynylaryl)ureas 1 selectively undergo either 6-exo-dig or 5-endo-dig cyclization (to give 4-methylene-3,4-quinazolin-2-ones 2 or indoles 3, respectively) depending on the choice of the metal, ligand, and reaction conditions. The best results (up to 96% yield) in the preparation of the hydroamination products 2 are achieved with the highly bulky NHC-stabilized cationic gold(I) complex Au(IPr). Conversely, ureas bearing an internal alkyne lead to the 5-endo-dig cyclization mode regardless of the gold(I) complex employed. Whereas the nature of the substituent at N-3 does not have any influence on the regiochemistry observed, it does, in some cases, affect the efficiency of these transformations.

摘要

3-取代的 1-(邻乙炔基芳基)脲 1 根据金属、配体和反应条件的选择，选择性地经历 6-endo-dig 或 5-endo-dig 环化（分别生成 4-亚甲基-3,4-喹唑啉-2-酮 2 或吲哚 3）。在制备氨化产物 2 时，采用高度空间位阻的 NHC 稳定的阳离子金（I）配合物 [Au(IPr)]+ 可获得最佳结果（最高产率达 96%）。相反，无论使用何种金（I）配合物，带有内部炔烃的脲都导致 5-endo-dig 环化模式。尽管 N-3 上取代基的性质对观察到的区域化学没有任何影响，但在某些情况下，它会影响这些转化的效率。