Bis(pyrazolyl)methane Copper Complexes as Robust and Efficient Catalysts for Sonogashira Couplings

A series of bis(pyrazolyl)methane copper complexes were found to catalyze a fast palladium‐free Sonogashira coupling reaction of several iodoarenes with terminal alkynes such as phenylacetylene, propargyl benzyl ether, and (tert‐butyl‐dimethyl)silylacetylene. These reactions proceed with CuCl2·2H2O (10 mol‐%) under aerobic conditions and the corresponding chelate ligand (10 mol‐%), with its tailored facial coordination mode, is crucial for the success of the reaction. The coupling can also be carried out in water with liquid aryl halides and a phase‐transfer catalyst. A series of bis(pyrazolyl)methane copper complexes were found to catalyze a fast palladium‐free Sonogashira coupling reaction of various iodoarenes with terminal alkynes. The reactions proceed under aerobic conditions, which makes this system synthetically highly useful. For liquid electrophiles, a substitution of DMF with water is possible when a phase‐transfer catalyst is provided.