Unlikeliness of Pd-Free Gold(I)-Catalyzed Sonogashira Coupling Reactions

The Sonogashira coupling reaction is not catalyzed by Aul/dppe in the absence of Pd complexes. However, addition of 0.1 mol % of Pd(0) led to efficient cross-coupling reactions. The most plausible catalytic cycles for the Au-catalyzed cross-coupling reactions have been examined and are unlikely in the absence of Pd contamination.