Copper-catalyzed coupling of imidazoles and pyrazoles with 1,1-dibromo-1-alkenes: a distinct approach for direct N-alkynylation of heteroarenes
摘要:
The direct N-alkynylation of heteroarenes, imidazoles, and pyrazoles with 1,1-dibromo-1-alkene has been carried out for the first time using [Cu(Phen)PPh3Br] (as a catalyst) and Cs2CO3 in DMSO at 80 degrees C. The products are formed in good to high yields (66-85%) within 3 h. No side products could be detected. (C) 2011 Elsevier Ltd. All rights reserved.
The couplingreaction of imidazoles and pyrazoles with bromoacetylenes has efficiently been carried out under ligand-free conditions in the presence of copper(II) oxide as the catalyst using potassium hydroxide in 1,4-dioxane at 80 ˚C. The method is a simpler access to N-alk-1-ynyl- and/or N-(2-bromovinyl)-substituted heteroarenes. couplingreaction - ligand-free conditions - copper(II) oxide - N-alkynylheteroarene