The Sonogashira reaction is known since 1975 and allows the coupling of terminal alkynes with vinylic and arylic halides. The major drawbacks of the Sonogashira reaction are the toxicity, the high cost of palladium salts and the requirement of inert gas conditions.
In conclusion we have shown that bis(pyrazolyl)methane copper(II) complexes are valuable new catalysts in the palladium-free copper-catalysed and aerobic Sonogashira reaction. A large array of iodoarenes and acetylenes can be converted to the desired cross-coupling products. Most remarkable is the excellent reaction rate, resulting from the use of the bis(pyrazolyl)methane copper catalysts. Moreover, the temperature can be lowered to 80 °C with still short reaction times. Further investigations will be focused on the activation of bromo- and chloroarenes and mechanistic studies.