DFT Studies on Metal-Controlled Regioselective Amination of N-Acylpyrazoles with Azodicarboxylates

Density functional theory calculations were carried out to study the reaction mechanisms of Ag(I)- and Zn(II)-catalyzed amination of unsaturated N-acylpyrazoles with azodicarboxylates. Our theoretical investigation focused on the origin of the metal-controlled regioselectivity (gamma- versus alpha-amination). Through our calculations, it was found that the amination reactions occur via metal-dienolate intermediates, in which the Ag(I) center prefers to coordinate with the alpha-carbon or the pyrazolyl N-donor site of the dienolate ligand, while the Zn(II) center prefers to coordinate with the O-donor of the dienolate ligand. The different site preferences for coordination with dienolate between the Ag(I) and Zn(II) metal centers play the key roles in the different regioselectivity observed experimentally.