Synthesis of Bicyclic Imidazoles via [2 + 3] Cycloaddition between Nitriles and Regioselectively Generated α-Imino Gold Carbene Intermediates
Yuanjing Xiao and Liming Zhang*
*Department of Chemistry and Biochemistry, University of California, Santa Barbara, California 93106, United States, Email: zhangchem.ucsb.edu
Y. Xiao, L. Zhang, Org. Lett., 2012, 14, 4662-4665.
DOI: 10.1021/ol302102h (free Supporting Information)
In a gold-catalyzed synthesis of bicyclic imidazoles, a highly electrophilic α-imino gold carbene intermediate can react with a weakly nucleophilic nitrile, which is used as the reaction solvent, to deliver the desired product rapidly in an overall bimolecular [2 + 2 + 1] cycloaddition and in good yield. The competing intramolecular azide-alkyne click reaction, although likely also catalyzed by gold, is minimized by using AuCl3 as the catalyst.
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