NHC-Stabilized Gold(I) Complexes: Suitable Catalysts for 6-exo-dig Heterocyclization of 1-(o-Ethynylaryl)ureas

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...

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Bibliographic Details
Published in:Organic letters 2010-05, Vol.12 (9), p.1900-1903
Main Authors: Gimeno, Ana, Medio-Simón, Mercedes, de Arellano, Carmen Ramírez, Asensio, Gregorio, Cuenca, Ana B.
Format: Article
Language:English
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Summary: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.
ISSN:1523-7060
1523-7052
DOI:10.1021/ol100595s