Letters in Organic Chemistry - Volume 17, Issue 10, 2020

The cycloaddition reactions of 2,3-bis (ethylene sulfonyl)-1,3-butadiene with 2,3-dimethyl- 1,3-butadiene, cyclopentadiene, 2-methyl prop-2-enoate and ethyl vinyl ether have been theoretically studied using the DFT method at the MPWB1K/cc-pVDZ level of theory. There are two possible modes of participation in each reaction (2π and 4π electron), of which the 2π electron is preferred. The energy results indicate that formations of the [2+4] cycloadducts are favored kinetically. The stereoselectivity of the [2+4] cycloaddition reaction of 2,3-bis (ethylene sulfonyl)-1,3-butadiene with cyclopentane is the highest and the energy barrier for this process is the lowest.

Celecoxib containing pyrazole derivatives were synthesized by path aldol condensation of substituted ketone with trifluoroethyl acetate subsequently by cyclization of the formed chalcones with 4-methanesulfonylphenylhydrazine. Here, a one-pot synthesis of celecoxib and substituted analogues have been reported which are nonsteroidal anti-inflammatory drugs for their cyclooxygenase (COX) inhibition, anti-inflammatory activity and ulcerogenic liability. In order to intermediate work-up, a continuous one-pot synthesis has been developed, performing the entire reaction sequence that results in a shorter time with good yield.

Conformational behaviors of 2,5-dimethyl-1,4-dithiane-2,5-diol (compound 1), 2,5- dimethyl-1,4-dithiane-2,5-dithiol (compound 2) and 2,5-dimethyl-1,4-dithiane-2,5-diselenol (compound 3) were investigated by the B3LYP/6-311+G **, the M06-2X/aug-ccpvdz levels of theory and natural bond orbital NBO analysis. The structures and the structural parameters of the mentioned molecules were optimized by the B3LYP and the M06-2X methods. We assessed the roles and contributions of the effective factors in the conformational properties of the mentioned compounds by means of the B3LYP and M06-2X levels of theory and the NBO interpretations. The stereoelectronic effects of the mentioned molecules were studied using the NBO analysis. The results showed that the stereoelectronic effects were in favor of the (ax,ax) conformers (the most stable conformations), from compound 1 to compound 3; therefore, these effects have impacts on the conformational properties of compounds 1-3, and stabilization energies associated with LP2X→ σ*S1-C2 electron delocalization, where [X= O, S, and Se], for 1-ax, ax conformer has the greatest value between all of the other conformers. Therefore, according to the calculated thermodynamic parameters, the stability of the 1-ax, ax compound was justified by the presence of LP2X→σ*S1-C2 electron delocalization. A molecular orbital explanation was conducted to investigate the correlations between the linear combinations of natural bond orbitals in the HOMOs, LUMOs and the molecular reactivity parameters. There is a direct relationship between the stereoelectronic effects, molecular reactivity and thermodynamic parameters of compounds 1 to 3 as the harder ax, ax conformations with the greater stereoelectronic effects and ΔG(eq-ax) values are more stable than their corresponding eq, eq conformers. Besides frontier molecular orbitals (FMOs), mapped molecular electrostatic potential (MEP) surfaces of conformations of compounds 1 to 3 were investigated.

A phosphaphenanthrene groups containing soybean oil based polyol (DSBP) was synthesized by epoxidized soybean oil (ESO) and 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Soybean oil based polyol (HSBP) was synthesized by ESO and H2O. The chemical structure of DSBP and HSBP were characterized with FT-IR and 1H NMR. The corresponding rigid polyurethane foams (RPUFs) were prepared by mixing DSBP with HSBP. The results revealed apparent density and compression strength of RPUFs decreased with increasing the DSBP content. The cell structure of RPUFs was examined by scanning electron microscope (SEM) which displayed the cells as spherical or polyhedral. The thermal degradation and flame retardancy of RPUFs were investigated by thermogravimetric analysis, limiting oxygen index (LOI), and UL 94 vertical burning test. The degradation activation energy (Ea) of first degradation stage reduced from 80.05 kJ/mol to 37.84 kJ/mol with 80 wt% DSBP. The RUPF with 80 wt% DSBP achieved UL94 V-0 rating and LOI 28.3. The results showed that the flame retardant effect was mainly in both gas phase and condensed phase.

The aim of this study was to synthesize and evaluate the biological activity of pyrazole derivatives, in particular, to perform a “greener” one-pot synthesis using a solvent-free method as an alternative strategy for synthesizing hydrazono/diazenyl-pyridine-pyrazole hybrid molecules with potential anticancer activity. Effective treatment for all types of cancers is still a long way in the future due to the severe adverse drug reactions and drug resistance associated with current drugs. Therefore, there is a pressing need to develop safer and more effective anticancer agents. In this context, some hybrid analogues containing the bioactive pharmacophores viz. pyrazole, pyridine, and diazo scaffolds were synthesized by one-pot method. Herein, we describe the expedient synthesis of pyrazoles by a onepot three-component condensation of ethyl acetoacetate/acetylacetone, isoniazid, and arenediazonium salts under solvent-free conditions, and the evaluation of their cytotoxicity using a sulforhodamine B assay on three cancer cell lines. Molecular docking studies employing tyrosine kinase were also carried out to evaluate the binding mode of the pyrazole derivatives under study. 1-(4-Pyridinylcarbonyl)-3- methyl-4-(2-arylhydrazono)-2-pyrazolin-5-ones and [4-(2-aryldiazenyl)-3,5-dimethyl-1H-pyrazol-1- yl]-4-pyridinylmethanones, previously described, were prepared using an improved procedure. Among these ten products, 1-isonicotinoyl-3-methyl-4-[2-(4-nitrophenyl)hydrazono]-2-pyrazolin-5-one (1f) displayed promising anticancer activity against the MCF-7, HepG2 and HCT-116 cell lines, with an IC50 value in the range of 0.2-3.4 μM. In summary, our findings suggest that pyrazoles containing hydrazono/ diazenyl and pyridine pharmacophores constitute promising scaffolds for the development of new anticancer agents.

Serious fungal infections are increasing worldwide and have become a great concern in the medical field since antifungal drugs are restricted to a few drug classes. This work aims to evaluate the antifungal activity of a series of 5-amino-1-aryl-3-methyl-1H-pyrazole-4-carbonitriles (1a-g) and to establish a structure-activity relationship (SAR). The synthesis of these compounds was carried out in a single step followed by cyclization in good to excellent yields i.e. 73-94%. The chemical structures were confirmed by melting point, IR, 1H-NMR, 13C-NMR, and HRMS. These seven compounds were submitted to the disk diffusion test against Candida spp. and the active compound was evaluated by means of the microdilution method to determine the minimum inhibitory concentration (MIC). In addition, the stereo electronic descriptors were evaluated and pharmacokinetic and toxicological properties were calculated to predict the potential of these compounds as a drug. All the compounds presented good theoretical physicochemical parameters and one of them showed reasonably good antifungal activity.

In the chlorination of N-[2-aryl-1-(1-piperidinylcarbonyl)ethenyl]arenecarboxamides, it has been found that a derivative having two methoxy substituents on the arenecarbonyl ring undergoes chlorination on the same ring rather than converting into the expected enamine bond chlorination product. Based on the above results, the chlorination of benzamides/nicotinamides by sulfuryl chloride (SO2Cl2) has been studied. We developed a method of synthesizing aromatic chlorinated compounds by treating aromatic amides or nitriles with SO2Cl2 in dichloromethane at 0oC without catalyst. This is a new mild method and gives good yields, especially when benzene ring is substituted by amide or cyano group together with the alkoxy group.

Dipyrromethanes are useful intermediates in the synthesis of porphyrins and their analogs. In this paper, we report the synthesis of a new bis(dipyrromethane) {(E)-1,2-bis[4-[di(1H-pyrrol-2- yl)methyl]phenyl]ethene}, from (E)-4,4'-1,2-ethenediylbis(benzaldehyde), showing a long resonance chain with improved UV spectrometric properties. This product has high potential in the synthesis of new bis(porphyrins) or other related compounds.

Racemic dicarboxylic acids were synthesized from the Diels-Alder cycloaddition reactions which formed the dibenzobarrelene and norbornene skeletons. The pure enantiomers of these compounds were obtained using brucine as the chiral auxiliary. Novel C2-symmetric chiral benzimidazole derivatives were synthesized from the reaction of the diaminobenzene and enantiomeric dicarboxylic acids in the presence of boric acid.

In this work, some new 2-[(3,4-dichlorophenyl)methyl]-1H-benzimidazole derivatives containing different five-membered heterocycles like 1,3,4-oxadiazole, 1,3,4-triazole, and 1,3,4- thiadiazole moieties were designed and efficiently synthesized starting from 2-[(3,4-dichlorophenyl) methyl]-1H-benzimidazole. The products were screened for their in vitro antioxidant and α-glucosidase inhibitory activities. Among the synthesized compounds, some of them showed efficient α-glucosidase inhibition with IC50 values ranging between 16.05 ± 0.94 and 77.02 ± 1.12 μg/mL when they were compared with the standard α-glucosidase inhibitor acarbose having IC50 value 12.04 ± 0.68 μg/mL. The antioxidant activity of all products was screened by using various in vitro antioxidant assays, including CUPric Reducing Antioxidant Capacity (CUPRAC) and Ferric Reducing Antioxidant Power (FRAP) assays. Also, the radical scavenging activities of the products were assayed by using the ABTS method.