A Copper-Free Procedure for the Palladium-Catalyzed Sonogashira Reaction of Aryl Bromides with Terminal Alkynes at Room Temperature

The catalyst system Pd2(dba)3/P(tBu)3 was found to promote the Sonogashira reaction of aryl bromides at room temperature and without CuI as the co-catalyst in high yield. The catalyst system was identified from a library of 58 potential ligands by the application of a color assay. The reaction conditions allow the use of only 0.5 mol-% palladium and ligand with reagent grade chemicals.