1224970-07-3Relevant academic research and scientific papers
NHC-stabilized gold(I) complexes: Suitable catalysts for 6-exo-dig heterocyclization of 1-(o-Ethynylaryl)ureas
Gimeno, Ana,Medio-Simon, Mercedes,De Arellano, Carmen Ramirez,Asensio, Gregorio,Cuenca, Ana B.
scheme or table, p. 1900 - 1903 (2010/06/21)
Figure presented 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.
