An efficient copper-catalyzed formation of highly substituted pyrazoles using molecular oxygen as the oxidant

An efficient Cu-catalyzed formation of tetra-substituted pyrazoles is reported. In this atom economic process, readily available enamines and nitriles are reacted by C-C and N-N bond formation. Oxygen has been successfully used as the oxidant, which has important economic and environmental advantages. A broad scope of enamines and nitriles can be utilized in this process.