Theoretical studies on copper-catalyzed arylation of nitrogen heterocycles from benzenediazonium acetate under ligand-free conditions

The density functional theory (DFT) method was used to investigate the mechanism of ligand-free copper-catalyzed arylation of nitrogen heterocycles from benzenediazonium acetate. Two possible mechanisms, single electron transfer and oxidative addition/reductive elimination reaction mechanism were investigated for two possible Cu(I) complexes in the reaction solution. Complex 1 has an acetate and a pyrazole ligand coordinated to Cu(I), and complex 2 has two pyrazole ligands coordinated to Cu(I). Both Cu(I) complexes have sufficiently low activation energy barriers for oxidative addition/reductive elimination reactions. Activation energy barrier for single electron transfer reaction is significantly higher than oxidative addition/reductive elimination reaction.