The [3+2] cycloaddition (32CA) reactions of N-benzylcyclohexylnitrone 1 with methyl-3-butenoate 2 have been studied within molecular electron density theory (MEDT) at the B3LYP/6-311++G(d,p) level of theory. These zwitterionic type 32CA reactions occur through a one-step mechanism. The 32CA reactions undergo two pairs of stereo- and regioisomeric reaction paths to form four different products, 3, 4, 5 and 6. The reaction paths are irreversible due to the exothermic character of −18.5 and −12.4 kcal mol⁻¹. The 32CA reaction leading to the formation of cycloadduct 3 presents the lowest activation enthalpy compared to the other path due to a slight increase in polar character evident from the global electron density transfer (GEDT) at the transition states and along the reaction path. The bonding evolution theory (BET) study suggests that these 32CA reactions occur through the coupling of pseudoradical centers and the formation of new C–C and C–O covalent bonds has not been started in the transition states.

The photocatalytic degradation of Toluidine Blue dye (TB) in aqueous solution was investigated under UV light in the presence of magnesium oxide (MgO) as a photocatalyst at different operating parameters. The operating conditions were photocatalyst dose, initial dye concentration and the pH of the solution. Increasing of photocatalyst dose from 10 to 70 mg enhanced the degradation rate of TB dye. However, the increasing of TB dye concentration from 2 to 8 mg/L negatively affected the degradation rate. It was found that the percent of dye removal reached the maximum value at high acidic medium. In dark condition, 15 % of dye was adsorbed by MgO. Furthermore, the kinetics involved in the degradation of TB dye was examined and the degradation was found to follow pseudo first order kinetic model.

A Molecular Electron Density Theory (MEDT) study is presented here for [3+2] cycloaddition (32CA) reactions of three trimethylsilyldiazoalkanes with diethyl fumarate. The presence of silicon bonded to the carbon of these silyldiazoalkanes changes its structure and reactivity from a pseudomonoradical to that of a zwitterionic one. A one-step mechanism is predicted for these polar zw-type 32CA reactions with activation enthalpies in CCl₄ between 8.0 and 19.7 kcal·mol⁻¹ at the MPWB1K (PCM)/6-311G(d,p) level of theory. The negative reaction Gibbs energies between −3.1 and −13.2 kcal·mole⁻¹ in CCl₄ suggests exergonic character, making the reactions irreversible. Analysis of the sequential changes in the bonding pattern along the reaction paths characterizes these zw-type 32CA reactions. The increase in nucleophilic character of the trimethylsilyldiazoalkanes makes these 32CA reactions more polar. Consequently, the activation enthalpies are decreased and the TSs require less energy cost. Non-covalent interactions at the TSs account for the stereoselectivity found in these 32CA reactions involving the bulky trimethylsilyl group.

In this study, we have investigated the reaction mechanism of the intramolecular [3+2] cycloaddition (32CA) process involving a nitrile oxide-heterocycle system through molecular electron density theory (MEDT). Density functional theory (DFT) calculations at the B3LYP/6-311++G(d,p) level of approximation have been performed to explore both endo and exo stereoisomeric pathways in benzene as a solvent. The results clearly indicate that the exo path is both thermodynamically and kinetically preferred, consistent with experimental findings. This preference is shown by reduced activation energies and greater negative Gibbs free energies for the exo product relative to the endo product. The bonding evolution theory (BET) analysis, in combination with ELF topological analysis, unraveled a stepwise mechanism that involves the formation of nitrogen lone pairs followed by the formation of C–C and C–O bonds. This mechanistic interpretation points out the asynchronicity of the bond-forming process, and the exo pathway is found to be less asynchronous compared to the endo one. Moreover, molecular docking analyses revealed that the exo product has considerable binding affinity to the 1CIN protease, indicating its potential as a therapeutic inhibitor. Moreover, drug-likeness evaluations verified that the compounds adhere to Lipinski's Rule of Five, signifying advantageous pharmacokinetic characteristics. This extensive work combines theoretical and computational approaches to clarify the intricate processes of 32CA reactions, offering significant insights into their synthetic applications and possible medicinal benefits.

The [3 + 2] cycloaddition between C-( d -glucoso)- N -methyl nitrone and 1 H -pyrrole-2,5-dione proceeds via an asynchronous one-step mechanism. The endo product shows strong 1CIN protease binding and promising drug-like properties.