Mechanochemical synthesis and cycloaddition reactions of fluoro nitrone under solvent‐free conditions and potential antimicrobial activities of the cycloadducts

Chromatography Scrutiny, Molecular Docking, Clarifying the Selectivities and the Mechanism of [3 + 2] Cycloloaddition Reaction between Linallol and Chlorobenzene-Nitrile-oxide

Employing the Molecular Electron Density Theory, [3 + 2] cycloaddition processes between 4-chlorobenzenenitrileoxide and linalool, have been applied using the DFT/B3LYP/6-311(d,p) method, activation, reaction energies and the reactivity indices are calculated. In an investigation of conceptual DFT indices, LIL-1 will contribute to this reaction as a nucleophile, whilst NOX-2 will participate as an electrophile. This cyclization is regio, chemo and stereospecific, as demonstrated by the reaction and activation energies, in clear agreement with the experiment's results, in addition, ELF analysis revealed that the mechanism for this cycloaddition occurs in two steps. Furthermore, a docking study was conducted on the products studied, and the interaction with the protein protease COVID-19 (PDB ID: 6LU7), our results indicate that the presence of the -OH group increases the affinity of these products, moreover, adsorption study by chromatography was made on silica gel as support; our outcome reveals that the -OH group creates an intramolecular hydrogen bond in the product P2, while in the product P3 will create a hydrogen bond with the silica gel which makes the two products P2 and P3 are very easy to separate by chromatography, this result is in excellent agreement with the Rf retention value. The study might provide a fundamental for developing natural anti-viral compound in promoting human health.

Insights into the mechanism of [3+2] cycloaddition reactions between N-benzyl fluoro nitrone and maleimides, its selectivity and solvent effects

We present a theoretical study of the [3+2] cycloaddition (32CA) reactions of N-benzyl fluoro nitrone with a series of maleimides producing isoxazolidines. We use the Molecular Electron Density Theory at the MPWB1K/6-311G(d) level. We focus on the reaction mechanism, selectivity, solvent, and temperature effects. In addition, we perform topological analyses at the minimal and transition states to identify the intermolecular interactions. Electron Localization Function approach classifies the N-benzyl fluoro nitrone as zwitterionic (zw-) three-atom components (TACs), associated with a high energy barrier. The low polar character of the reaction is evaluated using the Conceptual Density Functional Theory analysis of the reactants, confirmed by the low global electron density transfer computed at the transition states. Computations show that these 32CA reactions follow a one-step mechanism under kinetic control, with highly asynchronous bond formation and no new covalent bond is formed at the TS. Besides, the potential energy surfaces along the reaction pathways in gas phase and in solvent are mapped. The corresponding Gibbs free energy profiles reveal that the exo-cycloadducts are kinetically and thermodynamically more favored than endo-cycloadducts, in agreement with the exo-selectivity observed experimentally. In particular, we found that solvent and temperature did not affect this selectivity and mainly influence the activation energies and the exothermic character of these 32CA reactions.

Sustainable Synthesis of a Potent and Selective 5-HT7 Receptor Antagonist Using a Mechanochemical Approach

A mechanochemical procedure was developed to obtain PZ-1361, a potent and selective 5-HT₇ receptor antagonist, with antidepressant properties in rodents. The elaborated protocol offered several advantages over classical batch synthesis, including improvement of the overall yield (from 34% to 64%), reduction of reaction time (from 60 to 5.5 h), limitation of the use of toxic solvents, and the formation of byproducts. This approach represents a rare example of the synthesis of biologically active compounds exclusively performed using mechanochemical reactions.