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.