Molecular mechanism of Hetero Diels-Alder reactions between (E)-1,1,1-trifluoro-3-nitrobut-2-enes and enamine systems in the light of Molecular Electron Density Theory

A New Insight into the Molecular Mechanism of the Reaction between 2-Methoxyfuran and Ethyl (Z)-3-phenyl-2-nitroprop-2-enoate: An Molecular Electron Density Theory (MEDT) Computational Study

The molecular mechanism of the reaction between 2-methoxyfuran and ethyl (Z)-3-phenyl-2-nitroprop-2-enoate was investigated using wb97xd/6-311+G(d,p)(PCM) quantum chemical calculations. It was found that the most probable reaction mechanism is fundamentally different from what was previously postulated. In particular, six possible zwitterionic intermediates were detected on the reaction pathway. Their formation is determined by the nature of local nucleophile/electrophile interactions. Additionally, the channel involving the formation of the exo-nitro Diels-Alder cycloadduct was completely ruled out. Finally, the electronic nature of the five- and six-membered nitronates as potential TACs was evaluated.

Full Regio- and Stereoselective Protocol for the Synthesis of New Nicotinoids via Cycloaddition Processes with the Participation of Trans-Substituted Nitroethenes: Comprehensive Experimental and MEDT Study

[3 + 2] Cycloaddition reactions with the participation of Z-C-(3-pyridyl)-N-methylnitrone and series of E-2-R-nitroethenes were both experimentally and theoretically explored in the framework of Molecular Electron Density Theory. It was found that all considered processes are realized under mild conditions and in full regio- and stereocontrol. The ELF analysis additionally showed that the studied reaction proceeds by a two-stage, one-step mechanism.

On the Question of the Formation of Nitro-Functionalized 2,4-Pyrazole Analogs on the Basis of Nitrylimine Molecular Systems and 3,3,3-Trichloro-1-Nitroprop-1-Ene

Experimental and theoretical studies on the reaction between (E)-3,3,3-trichloro-1-nitroprop-1-ene and N-(4-bromophenyl)-C-arylnitrylimine were performed. It was found that the title process unexpectedly led to 1-(4-bromophenyl)-3-phenyl-5-nitropyrazole instead of the expected Δ²-pyrazoline molecular system. This was the result of a unique CHCl₃ elimination process. The observed mechanism of transformation was explained in the framework of the molecular electron density theory (MEDT). The theoretical results showed that both of the possible channels of [3 + 2] cycloaddition were favorable from a kinetic point of view, due to which the creation of 1-(4-bromophenyl)-3-aryl-4-tricholomethyl-5-nitro-Δ²-pyrazoline was more probable. On the other hand, according to the experimental data, the presented reactions occurred with full regioselectivity.

The First Examples of [3+2] Cycloadditions with the Participation of (E)-3,3,3-Tribromo-1-Nitroprop-1-Ene

The first examples of [3+2] cycloaddition reactions between 3,3,3-tribromo-1-nitroprop-1-ene (TBMN) were explored on the basis of experimental and theoretical approaches. It was found that reactions involving TBMN and diarylnitrones realized with full regio- and stereoselectivity lead to respective 3,4-cis-4,5-trans-4-nitroisoxazolidines. The regioselecticity and the molecular mechanism of title processes was analyzed on the basis of the advanced DFT computational study.

Synthesis, evaluation of drug delivery potential, and the quantum chemical investigation on a molecular imprinted polymer for quetiapine antipsychotic; a joint experimental and density functional theory study

In this project, the quetiapine drug was used as the template for synthesis of a molecular imprinted polymer (MIP). The polymerization approach for preparation of this composite was precipitation, where methacrylic acid (MAA), ethylene glycol dimethacrylate (EGDMA), and 2,2-azobisissobutyronitrile (AIBN) were used as the functional monomer, the cross-linker, and the initiator, respectively. Scanning electron microscopy (SEM) showed that the diameter of the nanoparticles is about 70 nm. The adsorption rates of quetiapine to the MIP host were evaluated at different pHs, and the results showed that the highest adsorption values were obtained at pH = 7. Moreover, the kinetics of the adsorption process was detected to follow the Langmuir isotherm (R2 = 0.9926) and the pseudo-second-order kinetics (R2 = 0.9937). The results confirmed the high capability of the synthesized MIPs as pharmaceutical carriers for quetiapine. Furthermore, the kinetics of the drug release from the MIP follows the Higuchi model at the pHs of 5.8-6.8 and the Korsmeyer-Peppas model at the pHs of 1.2-5. Finally, in light of the density functional theory (DFT)-based quantum chemical descriptors, the polymer-quetiapine drug complex was designed and investigated. The results showed that there is a strong interaction between the host (polymer) and the guest (drug) due to several hydrogen bonds and other intermolecular (polar) interactions.

Mechanistic aspects of the synthesis of seven-membered internal nitronates via stepwise [4 + 3] cycloaddition involving conjugated nitroalkenes: Molecular Electron Density Theory computational study

The density functional theory computational study indicates the possibility of the synthesis of seven-membered internal nitronates via cycloaddition reactions involving Z-C-aryl-N-methylnitrones and E-2-aryl-1-cyano-1-nitroethenes. The detailed exploration of the reaction paths indicates a polar, stepwise reaction mechanism through the zwitterionic intermediate. Using bonding evolution theory (BET), we have deciphered the molecular mechanism of the [4 + 3] cycloaddition reaction between E-2-phenyl-1-cyano-1-nitroethene and Z-C-phenyl-N-methylnitrone. The BET study has revealed that the formation of two CO single bonds takes place in the same way, through the depopulation of NC and CC bonding regions and monosynaptic basins, respectively. The first O1C7 single bond was formed in the sixth phase, while the second C3O4 bond was formed in the last ninth phase.

On the Question of Stepwise [4+2] Cycloaddition Reactions and Their Stereochemical Aspects

Even at the end of the twentieth century, the view of the one-step [4+2] cycloaddition (Diels-Alder) reaction mechanism was widely accepted as the only possible one, regardless of the nature of the reaction components. Much has changed in the way these reactions are perceived since then. In particular, multi-step mechanisms with zwitterionic or diradical intermediates have been proposed for a number of processes. This review provided a critical analysis of such cases.

Understanding the molecular mechanism of γ-elimination of nitrous acid in the framework of the molecular electron density theory

The reactions of γ-dehydronitration of furaxanenitrolic acids have been studied within the density functional theory using molecular electron density theory scheme at the MPWB1K(PCM)/6-311G(d,p) level of theory. The alteration of bonding along the course of the reaction is studied in the topology of the electron density functional within the bonding evolution theory perspective. The characteristics of electron density changes indicate that we can distinguish six different phases in the nitrous acid extrusion from furaxanenitrolic acid 1a. These different phases related to the intrinsic reaction coordinate path of the analyzed reaction denote the non-concerted nature of the molecular mechanism.

Understanding the molecular mechanism of the stereoselective conversion of N-trialkylsilyloxy nitronates into bicyclic isoxazoline derivatives

The conversion of N-trialkylsilyloxy nitronates into bicyclic isoxazoline derivatives has been explored using the density functional theory method within the context of molecular electron density theory at the ωB97XD(PCM)/6-311G(d,p) level.

Participation of Phosphorylated Analogues of Nitroethene in Diels–Alder Reactions with Anthracene: A Molecular Electron Density Theory Study and Mechanistic Aspect

The structure and the contribution of the bis(2-chloroethyl) 2-nitro 1a and 2-bromo-2-nitroethenylphosphonates 1b with anthracene 2 in the Diels–Alder (DA) reactions have been studied within the Molecular Electron Density Theory (MEDT) at the B3LYP functional together with 6-31G(d), 6-31+G(d) and 6-31+G(d,p) basic sets. Analysis of the Conceptual Density Functional Theory (CDFT) reactivity indices indicates that 1a and 1b can be classified as a strong electrophile and marginal nucleophile, while 2 is classified as a strong electrophile and strong nucleophile. The studied DA reactions take place through a one-step mechanism. A Bonding Evolution Theory (BET) of the one path associated with the DA reaction of 1a with 2 indicates that it is associated with non-concerted two-stage one-step mechanism. BET analysis shows that the first C2-C3 single bond is formed in Phase VI, while the second C1-C6 single bond is formed in the Phase VIII. The formation of both single bonds occurs through the merging of two C2 and C3, C1 and C6 pseudoradical centers, respectively.