DFT Studies on Mechanism of Organocatalytic Metal-Free Click 32CA Reaction for Synthesis of NH-1,2,3-triazoles

• Published in: Catalysis letters 2024-03, Vol.154 (3), p.1134-1141
• Main Authors: Al-Hakim Badawi, Mohammad Abd, Al-Zaben, Maha I., Thomas, Renjith
• Format: Article
• Language: English
• Subjects: Catalysis; Chemical synthesis; Chemistry; Chemistry and Materials Science; Cycloaddition; Density functional theory; Free energy; Industrial Chemistry/Chemical Engineering; Organometallic Chemistry; Physical Chemistry; Solvents; Vapor phases
• ISSN: 1011-372X; 1572-879X
• DOI: 10.1007/s10562-023-04374-3

The mechanism of enamine-mediated organocatalytic [3 + 2] cycloaddition (32CA) reaction of Hagemann’s ester to p -toluenesulfonyl azide in the present L-proline as a catalyst has been investigated using M06-2X functional with the 6-31+G(d) basis set. The effects of the different solvents were studied with a 6-311+G(d,p) basis set. In addition, the effects of the keto ester substitutions: one model system M1 (R 1  = CH 3 and R 2  = H) and two real systems R2 (R 1  = R 2  = Me) and R3 (R 1  = Et and R 2  = Me) also studied in this work. DFT results indicated that the different solvents show the same effect, which leads to a decrease in the ΔG 298 along the reaction pathway compared to the gas phase. Moreover, the model system M1 has a lower activation free energy (17.5 kcal/mol) than real systems R2 and R3 by about 3.8 and 3.2 kcal/mol in the solution phase (DMSO), respectively. Analysis of the global and local reactivity indices of the reactants was performed in the gas and solution phases. Graphical Abstract