Quantum chemistry study on regioselectivity in ruthenium catalyzed synthesis of 1,5-disubstituted 1,2,3-triazoles

In this research, the origins of regioselective behavior of ruthenium catalyzed azide-alkyne cycloaddition reaction were assessed via the quantum chemistry approaches. In this respect, density functional theory calculations were performed to investigate the structural and energetic properties of regioisomeric triazole products and their corresponded transition states in the presence of ruthenium as the catalyst. Moreover, the solvation effects were examined via polarized continuum model computing in the presence of 1,2-dichloro ethane (1,2-DCE) and dimethyl formamide (DMF) to interpret the regioselectivity. In the next step, in order to present a more concise rationalization for the mechanistic role of ruthenium catalyst in regioselective synthesis of 1,5-disubstituted 1,2,3-triazoles, we assessed the topological properties of electron density in isomeric products and their corresponded transition states by employing the quantum theory of atoms in molecules. In this route, we concentrated on calculation of electron density, its laplacian and other electronic energy density indicators in some key bond critical points (BCPs) which have a significant role in regioselective production of 1,5-disubstituted 1,2,3-triazoles.