The concern of emergence of multi-station reaction pathways that might make stepwise the mechanism of the 1,3-dipolar cycloadditions of azides and alkynes

Energetic Aspects and Molecular Mechanism of 3-Nitro-substituted 2-Isoxazolines Formation via Nitrile N-Oxide [3+2] Cycloaddition: An MEDT Computational Study

Regioselectivity and the molecular mechanism of the [3+2] cycloaddition reaction between nitro-substituted formonitrile N-oxide 1 and electron-rich alkenes were explored on the basis of the wb97xd/6-311+G(d) (PCM) quantum chemical calculations. It was established that the thermodynamic factors allow for the formation of stable cycloadducts along all considered models. The analysis of the kinetic parameters of the main processes show that all [3+2] cycloadditions should be realized with full regioselectivity. In all cases, the formation of 5-substituted 3-nitro-2-isoxazolidines is clearly preferred. It is interesting that regiodirection is not determined by the local electrophile/nucleophile interactions but by steric effects. From a mechanistic point of view, all considered reactions should be treated as polar, one-step reactions. All attempts to locate the hypothetical zwitterionic intermediates along the cycloaddition paths were, however, not successful.

Application of the oxycodone templated molecular imprinted polymer in adsorption of the drug from human blood plasma as the real biological environment; a joint experimental and density functional theory study

In this project, we have synthesized and used a molecular imprinted polymer (MIP) for adsorption of oxycodone residue from the biological samples. Indeed, this study aims to develop a suitable method for determination of oxycodone drug residue in the human plasma using the common analysis methods. Therefore, the MIP was used for the solid phase extraction (MIP-SPE) approach in order to collect the oxycodone opioid and to concentrate it in the blood plasma samples. The extraction parameters such as adsorption time, pH, and the amount of sorbent in blood plasma were optimized and the capacity of loading amount (LA) for adsorbing it was determined. Moreover, a high performance liquid chromatography (HPLC)-UV detector method was validated and used for analyzing of the mentioned opioid extracted from plasma. The results showed that the limit of detection (LOD), and the limit of quantization (LOQ) for the developed MIP-SPE method were 1.24 ppb, and 3.76 ppb, respectively. Moreover, both of the MIP-, and non-imprinted polymers (NIP)-drug complexes were designed and were then optimized by the density functional theory (DFT) method. The results showed that the theoretical calculations supported the experimental data, confirming the favorability of adsorption of the drug by MIP compared to NIP.

An Industrial Approach to Production of Tofacitinib Citrate (TFC) as an Anti-COVID-19 Agent: A Joint Experimental and Theoretical Study

In this report, we have presented our experience about a facile method for synthesis of tofacitinib citrate (TFC). The developed analytical methods for identification and qualifications are also included. As TFC seems to be effective in treatment of the symptoms of COVID-19 (SARS family), manufacturing of this active pharmaceutical ingredient (API) could be helpful. The API of TFC was prepared from the diamine intermediate in an ambient and solvent-free condition. Elimination of the reaction solvent resulted in decreasing the cost and preventing the rejection of the organic volatile impurity (OVI) test. The final citrate addition step was carried out using water as a solvent (the citrate content was 37.5% by potentiometry). Moreover, the results of the Karl-Fischer (KF) titration analysis was about 0.24%, which showed that the use of water does not increase the water content of the crystal structure.

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.

Carbon fixation of CO2 via cyclic reactions with borane in gaseous atmosphere leading to formic acid (and metaboric acid); A potential energy surface (PES) study

Carbon dioxide (CO₂), a stable gaseous species, occupies the troposphere layer of the atmosphere. Following it, the environment gets warmer, and the ecosystem changes as a consequence of disrupting the natural order of our life. Due to this, in the present reasearch, the possibility of carbon fixation of CO₂ by using borane was investigated. To conduct this, each of the probable reaction channels between borane and CO₂ was investigated to find the fate of this species. The results indicate that among all the channels, the least energetic path for the reaction is reactant complex (RC) to TS (A-1) to Int (A-1) to TS (A-D) to formic acid (and further meta boric acid production from the transformation of boric acid). It shows that use of gaseous borane might lead to controlling these dangerous greenhouse gases which are threatening the present form of life on Earth, our beautiful, fragile home.

Recent Strategies in Transition-Metal-Catalyzed Sequential C–H Activation/Annulation for One-Step Construction of Functionalized Indazole Derivatives

Designing new synthetic strategies for indazoles is a prominent topic in contemporary research. The transition-metal-catalyzed C–H activation/annulation sequence has arisen as a favorable tool to construct functionalized indazole derivatives with improved tolerance in medicinal applications, functional flexibility, and structural complexity. In the current review article, we aim to outline and summarize the most common synthetic protocols to use in the synthesis of target indazoles via a transition-metal-catalyzed C–H activation/annulation sequence for the one-step synthesis of functionalized indazole derivatives. We categorized the text according to the metal salts used in the reactions. Some metal salts were used as catalysts, and others may have been used as oxidants and/or for the activation of precatalysts. The roles of some metal salts in the corresponding reaction mechanisms have not been identified. It can be expected that the current synopsis will provide accessible practical guidance to colleagues interested in the subject.

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

The molecular mechanism of the reaction of (E)-1,1,1-trifluoro-3-nitrobut-2-ene 1 with 3,3-dimethyl-2-morpholinobutene 2 has been studied within the Molecular Electron Density Theory (MEDT). This theoretical study confirm the possibility of the formation of zwitterionic structures in the first reaction stage. Interestingly, that localized zwitterions are however not common intermediates for identified in the postreaction mixture products. The further Bonding Evolution Theory (BET) study show, that the key, HDA reaction takes place in one-step but in a non-concerted manner since three stages are clearly identified. First the C5-C6 double bond breaks, then the C1-C2 bond breaks, and in the last phase we observed the formation of the C1-C6 single bond and V(C2) and V' (C2) pseudoradical centers in Z1 molecule. In turn, the molecular mechanism of the conversion of zwitterion Z1 to product 3 can be divided also in three groups in which we observed the disappearance of the two pseudoradical centers and formation O4-C5 single and C3-N3 double bonds, respectively.

Potential of graphene oxide as a drug delivery system for Sumatriptan: a detailed density functional theory study

The adsorption property of Sumatriptan drug onto graphene oxide (GO) was studied using density functional theory (DFT) calculations. All possible initial positions of drug adsorption were considered to find out which one is energetically favorable. According to the achieved findings, the stronger interactions occurred between the positively polarized parts of the Sumatriptan (i.e. hydrogen atoms of the-OH and -NH parts) and negatively polarized oxygen atoms of the GO. The presence of non-covalent interactions of GO and Sumatriptan was confirmed based on the determined geometrical parameters, electronic structure analysis results, and adsorption energies. Different parameters such as frontier molecular orbital (FMO), natural bond orbital (NBO), dipole moment, and solation energy were investigated. Global indices such as hardness, softness, chemical potential, and electrophilicity of all systems were calculated and compared. The adsorption energy values were determined within the range of -8.39 to -10.59 kcal/mol (-1.87 to -5.67 BSSE corrected) in the water solvent for different adsorption geometries. The obtained results show that GO can act as a promising carrier/sensor for Sumatriptan drug in practical application.Communicated by Ramaswamy H. Sarma.

A [1 + 2] cycloaddition instead of usual [2 + 3] cycloaddition between the B12N12 cluster and methyl azide: Potential energy surface calculations and Born–Oppenheimer molecular dynamics simulations

We have examined here the possibility of functionalization of the B12N12 cluster by methyl azide by means of a [2 + 3] cycloaddition reaction in analogy with the spontaneous functionalization of C20 fullerene using the same reaction. To achieve more reliable data, all possible interactions at different positions and orientations were considered by reaction channel study and potential energy surface calculations. Also, Born–Oppenheimer molecular dynamics simulations were used to find probable species which could emerge during the reactions.

Understanding the mechanism of the 1,3-dipolar cycloaddition reaction between a thioformaldehyde S-oxide and cyclobutadiene: Competition between the stepwise and concerted routes

Changing the mechanism of the widely used 1,3-dipolar cycloaddition reaction from its usual asynchronous one-step pattern to the rarely observed stepwise form leads to the emergence of intermediates, side products, and other impurities. Thus, it is crucial to determine the nature of the mechanism of the 1,3-dipolar cycloaddition reaction between a special 1,3-dipole and a specified dipolarophile (by theoretical methods) before using them for synthesizing a desired product. In this study, therefore, we have investigated the possibility of some probable intermediates emergence in the 1,3-dipolar cycloaddition reaction between cyclobutadiene and thioformaldehyde S-oxide. The results showed that emergence of Int (B) (−52.1 kcal mol−1) via transition state (B-1) is favorable both thermodynamically and kinetically (in comparison with all other stepwise routes). That is, developing probable impurities should not be neglected at least in the cases of the reactions between some thioformaldehyde S-oxide and some dipolarophiles.

Experimental and computational studies on the synthesis of diastereoselective natural-based Meldrum spiro dibenzofuran derivatives

Herein, a novel route to achieve chiral Meldrum spiro dibenzofuran derivatives was developed, which involved a 2,2-dimethyl-1,3-dioxane-4,6-dione (Meldrum's acid)-mediated Knoevenagel reaction of substituted aryl halides, followed by a Diels–Alder reaction with euparin as a natural compound.