Sonogashira Couplings Catalyzed by Collaborative (N-Heterocyclic Carbene)-Copper and -Palladium Complexes

A general protocol for the Sonogashira reaction using a 100:1 combination of (N-heterocyclic carbene)-Cu and (N-heterocyclic carbene)-Pd complexes is presented. Catalyst loadings of 1 mol % (NHC)-Cu and 0.01 mol % (NHC)-Pd allow for the coupling of aryl bromides and aryl alkynes, in air and in a non-anhydrous solvent, in high yields.