This study employs Molecular Electron Density Theory (MEDT) to explore the [3+2] cycloaddition mechanisms involving 1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene (2-R) and nitrile oxide (3-R). Density Functional Theory (DFT) calculations using the B3LYP/6-311(d,p) method were performed to determine reactivity indices, activation energies, and reaction energies. The conceptual DFT analysis indicates that 1-methyl-4-(prop-1-en-2-yl)cyclohex-1-ene 2-R acts as a nucleophile, while nitrile oxide 3-R functions as an electrophile. The reaction exhibits notable chemoselectivity and regioselectivity, supported by activation energies that align with experimental data. BET analysis suggests a one-step mechanism with asynchronous bond formation. Additionally, molecular docking studies of the reaction products against HIV-1 and COVID-19 reveal that the presence of oxygen and nitrogen atoms enhances the interaction energy with proteins, indicating potential therapeutic benefits.

Molecular electron density theory has been performed with the B3LYP/6-31(d,p) method to study the [3+2] cycloaddition processes between azidobenzene and propionaldehyde, the reactivity indices, activation and reaction energies are computed. The reaction and activation energies indicate that this [3+2] cycloaddition reaction is regiospecific, in good agreement with the experimental results. ELF examination revealed that the mechanism of these cycloaddition reactions takes place in two steps. In addition, a docking approach was performed on the products investigated, and the interaction with the protein protease COVID-19 (PDB ID: 6LU7), the results confirm that the presence of triazole and isoxazole rings increases the affinity of these products.

Application of the Molecular Electron Density Theory (MEDT) for the exploration of the [3+2] cycloaddition processes between methyl propynoate 1 and difluoromethyldiazomethane T-1, have been implemented using the DFT/B3LYP/6-311(d,p) level of theory. According to an examination of conceptual DFT indices, difluoromethyldiazomethane (T-1) participates in this reaction as a nucleophile, while methyl propynoate (1) should be considered as an electrophile. This cyclization is regiospecific, as evidenced by the activation and reaction energies, this agrees with the experiment's findings. It was discovered throughout ELF analysis that analyzed [3+2] cycloaddition is realised by a two-step mechanism. In addition, study of interactions of the products studied in this paper with the protein protease Covid-19 (PDB ID: 7R98) were carried out, by means of molecular docking study). The results indicate that the occurrence of the transfer of the proton to the nitrogen atom, increases the affinity of these products to the protein (CA32-F1 and CA32-F2).