Heterocyclic Organic Compounds Research Articles

A one-step synthesis of substituted benzo- and pyridine-fused 1H-imidazoles

Substituted benzimidazoles and pyrimidazoles are an important group of heterocyclic aromatic organic compounds in the field of medicinal chemistry. A one-step microwave accelerated synthesis of substituted benzo- and pyridine-fused 1H-imidazoles has been described. Mechanistically, the reaction proceeds by reacting substituted 2-fluoronitrobenzene and substituted arylamine through the formation of N-hydroxy intermediate, which at higher temperature cleaves to afford the desired product. This approach achieved reductions in reaction times, higher yields, cleaner reactions than the previously described synthetic processes.

Pyrene-Benzimidazole Derivatives as Novel Blue Emitters for OLEDs.

Three novel small organic heterocyclic compounds: 2-(1,2-diphenyl)-1H-benzimidazole-7-tert-butylpyrene (compound A), 1,3-di(1,2-diphenyl)-1H-benzimidazole-7-tert-butylpyrene (compound B), and 1,3,6,8-tetra(1,2-diphenyl)-1H-benzimidazolepyrene (compound C) were synthesized and characterized for possible applications as blue OLED emitters. The specific molecular design targeted decreasing intermolecular aggregation and disrupting crystallinity in the solid-state, in order to reduce dye aggregation, and thus obtain efficient pure blue photo- and electroluminescence. Accordingly, the new compounds displayed reasonably high spectral purity in both solution- and solid-states with average CIE coordinates of (0.160 ± 0.005, 0.029 ± 0.009) in solution and (0.152 ± 0.007, 0.126 ± 0.005) in solid-state. These compounds showed a systematic decrease in degree of crystallinity and intermolecular aggregation due to increasing steric hindrance, as revealed using powder X-ray diffraction analysis and spectroscopic studies. An organic light-emitting diode (OLED) prototype fabricated using compound B as the non-doped emissive layer displayed an external quantum efficiency (EQE) of 0.35 (±0.04)% and luminance 100 (±6) cd m−2 at 5.5 V with an essentially pure blue electroluminescence corresponding to CIE coordinates of (0.1482, 0.1300). The highest EQE observed from this OLED prototype was 4.3 (±0.3)% at 3.5 V, and the highest luminance of 290 (±10) cd m−2 at 7.5 V. These values were found comparable to characteristics of the best pure blue OLED devices based on simple fluorescent small-molecule organic chromophores.

Computational and experimental studies of the inhibitory effect of imidazole derivatives for the corrosion of copper in an acid medium

The inhibitory efficiencies of the molecules tested are determined using weight loss measurements, potentiodynamic polarization and electrochemical impedance (EIS). The adsorption of 1-Methylimidazole and 1H-benzimidazole on metallic surface reinforced with SEM-EDS and UV–Visible analysis of copper surface. These imidazole derivatives are heterocyclic organic compounds containing nitrogen atoms and are of great interest because of their multiple pharmacological activities. A theoretical simulation is achieved for the series of systems studied using density functional theory (DFT) to determine their electronic, structural and energetic properties. Monte Carlo simulation was performed to know well of the relationship between the inhibition ability and molecular structure of imidazole derivatives, the results of the potentiodynamic polarization indicate that the imidazole derivatives are mixed type inhibitors. These reduce the speed of the corrosion process for an optimal concentration of 10-3M. Electrochemical impedance spectroscopy (EIS) shows the presence of a single capacitive loop in favor of the charge transfer mechanism, the corrosion inhibition efficiency of 1-Methylimidazole and and 1H-benzimidazole exceeds approximately 66% 80% respectively. The adsorption of the compounds was found to obey Langmuir adsorption isotherm. A good agreement is observed between the results obtained by the different experimental techniques. Theory-experience correlations are established.

In silico designing of some Benzimidazole derivatives for Anti-fungal activity

Fungus is a kind of living organism and yeast mould and mushrooms are types of fungi. The fungal infections are caused by the fungus. A fungus that invades the tissue can cause a disease that confined to the skin, spread into tissue, bone and organs or affect the whole body. Benzimidazole is a class of heterocyclic aromatic organic compound which posses pharmacological activities including antifungal, antitumor, antiparasitic, analgesic etc. Insilico methods can be used to identify target molecules using bioinformatics tool. The aim of our study was to conduct the insilico drug designing of some benzimidazole derivatives having antifungal activities. In our study the insilico drug design was performed using Biovia discovery studio.

English

The rising antibiotic resistance is urging researchers to explore for new forms of antibiotics, notably from soil microorganisms such as Bacillus species. This study aimed to screen Bacillus strains from soil samples in Sudan for antifungal activity and to review relevant compounds from members of the genus in the literature. Out of 10 isolates from soil in Sudan, the strain JS6 (DSM 28831) was found active against representative zygomycete fungi and consequently subjected to thorough identification and chemical analyses of secondary metabolites. Confirmation of the initially identified Bacillus spp. was done using 16S rDNA gene sequence analysis which indicated a novel species (accession MF099872) that is closely related to Bacillus siamensis, Bacillus amyloliquefaciens, and Bacillus nakamurai. The crude culture-free filtrate and both chloroform and ethyl acetate extracts authenticated the initial antifungal activity of this strain, which exceeded that of amphotericin B, a standard antifungal agent. GC-MS results of the extracts revealed 32 compounds which included long-chain fatty acids, fatty acid methyl esters, alkaloids, and alcoholic compounds. Seven biologically active compounds were identified from Bacillus spp. strain JS6 and are equally found in the literature originating from plant or microbial sources. In the literature, these compounds show various activities such as antifungal, antioxidant, hypocholesterolemic, nematicide, pesticide, antiandrogenic, flavour, haemolytic, alpha reductase inhibitor, and other antimicrobial activities. The analysis identified a major unique antifungal peak (rt, 23.142; area, 25.36%) as 5,10-Diethoxy-2,3,7,8-tetrahydro-1H,6H-dipyrrolo[1,2-a:1',2'-d]pyrazine, a heterocyclic aromatic organic compound, that has been previously detected in Lactobacillus casei. Key words:  Bacillus species, chromatography, TLC, GC-MS, soil, aromatic organic compounds.

NLO potential exploration for D–π–A heterocyclic organic compounds by incorporation of various π-linkers and acceptor units

Heterocyclic compounds with excellent nonlinear optical (NLO) properties are highly significant and have many potentials uses in various fields such as nuclear science, optoelectronics etc. Herein, an organic dye JK-201 was used theoretically to design a series of novel D-π-A based NLO molecules ( DTA1-DTA12 ). This novel series of NLO molecules was quantum chemically designed by structural tailoring at the 1st π-spacer and acceptors unit of the JK-201 molecule. To explore the effect of spacers and acceptors on the electronic, photophysical, and NLO properties of DTA1-DTA12 , density functional theory (DFT) investigations were performed for different simulation analyses. UV–Vis spectra revealed that all these novel compounds exhibited broader absorption spectra with the largest shift and a narrowed bandgap (1.84–2.07 eV ) compared to the parent molecule ( JK-201 ). Among all the designed compounds, the largest redshift was examined in DTA11 (538.99 nm ). Furthermore, with the help of frontier molecular orbital (FMO) study, charge transfer processes between the orbitals and chemical reactivity of designed molecules were explained. Moreover, the Energy gap (E LUMO -E HOMO ) was also used to express global reactivity parameters (GRPs). These GRP findings evaluated that all molecules ( DTA1-DTA12 ) had higher global softness ( σ = 13.15–14.77 a.u ) and lower hardness ( η = 0.034–0.038 a.u ) values, which indicated that these compounds were more reactive. Nevertheless, significantly higher NLO behavior was examined in all compounds. Overall, compound DTA5 showed a larger value of the linear polarizability ( <α> = 2868.08 a.u .), while compound DTA12 displayed a larger hyperpolarizability ( β total = 268494.71 a.u ) value. This present work presented that by controlling the type of π-spacer and acceptor units, metal-free NLO materials can be designed, which can be valuable for hi-tech NLO applications.

A Brief Introduction to Porphyrin Compounds used in Tumor Imaging and Therapies.

As a group of heterocyclic macrocycle organic natural compounds occurring universally in animal tissues and plants, porphyrins are composed of four modified pyrrole subunits. Porphyrin analogues/ derivatives possess multiple biochemical properties because of their unique structures and have been extensively investigated in cancer treatment. Studies have shown that porphyrins and their derivatives have the ability to locate tumor cells in a variety of human cancers, and these compounds not only exhibit potent therapeutic effects as photodynamic agents but also show promising properties in medicinal imaging, such as MRI, photoacoustic imaging, fluorescence imaging, and PET/SPECT imaging. This paper reviews the recent reports of porphyrin derivatives as therapeutic agents used in tumor therapies, such as sonodynamic therapy, photodynamic therapy and radiotherapy, as well as the imaging agents for multimodality tumor imaging. The limitations of porphyrin-based compounds in tumor treatments and future prospects are also summarized.

Synthesis, Characterization and Anti-Microbial Activity of Novel Pyramidine Derivatives

Pyrimidine is a heterocyclic aromatic organic compound similar to benzene and pyridine, containing two nitrogen atoms at positions 1 and 3 of the six-member ring. Three nucleobases found in nucleic acids, cytosine (C), thymine (T), and uracil (U), are pyrimidine derivatives. A pyrimidine has many properties in common with pyridine, as the number of nitrogen atoms in the ring increases the ring pi electrons become less energetic and electrophilic aromatic substitution gets more difficult while nucleophilic aromatic substitution gets easier. Chalcones react with aminoguanidine to give intermediate compounds which on further reacts with substituted ketones to give Pyramidine derivatives. A total of 6 compounds were synthesized from one scheme and they were recrystallized by appropriate solvents. They were identified and characterized by various spectral methods. In the present study, all synthesized compounds tested for anti bacterial activity and anti-fungal activity. They shown significant activity when compared with standard drug Streptomycin and Miconazole respectively. Keywords: Pyramidines, Characterization, Streptomycin, Miconazole, Anti-microbial activity.

Hygroscopicity Enhancement of Low Temperature Hydrothermally Synthesized Zinc Oxide Nanostructure with Heterocyclic Organic Compound for Humidity Sensitization

Materials that have hygroscopic capabilities are potent sensing elements for humidity sensors. The hygroscopic behaviour of zinc oxide (ZnO) with modified nanostructure was synthesized and characterized. Heterocyclic additive was added on ZnO to improve its hygroscopic capability for humidity sensitization. ZnO capability of water molecule adsorption was tested with a hygroscopic characterization method adapted from American Society for Testing and Materials (ASTM) method for hygroscopic determination. It was found that inclusion of additive improves the water retention and release ZnO, making it more viable for use in sensors that take advantage of mechanical strain due to weight for humidity determination. The hygroscopic behaviour was observed in the steeper gradient on the mass change during humidity exposure to the ZnO compound with the additive compared to non-additive ZnO. Furthermore, the additive loaded ZnO showed greater reliable regression, R2 value (3.56 %) compared to the non-additive ZnO sample. Crystal analysis via X-ray diffraction (XRD) revealed increment on ZnO characteristic peaks (002) and (101) upon addition of the organic compound to the ZnO which influence the nanostructure of the material. Field emission scanning electron microscopy (FESEM) indicates porous and hemispherical nanostructure. Elemental analysis showed minimal impurities present on both ZnO and additive loaded ZnO. The hygroscopic capabilities of ZnO synthesized with low temperature hydrothermal technique allows for implementation in many humidity sensing options required by industries of various fields.

Modeling Ammonia and Its Uptake by Secondary Organic Aerosol Over China

AbstractAtmospheric ammonia (NH3) can affect nitrogen deposition, particle acidity, and gas‐particle partitioning. Although the inorganic chemistry of NH3 in fine particulate (PM2.5) formation are well‐constrained, the understanding of interactions between NH3 and secondary organic aerosol (SOA) are rather insufficient until recently. Laboratory studies indicate that NH3 molecule can react with SOA then forms nitrogen‐containing organic compounds (NOCs), which can further react to form heterocyclic organic compounds. In this study, we use a modified version of the CMAQ model to simulate the potential importance of the SOA‐ammonia uptake mechanism on air quality over China in summer and winter 2017, considering a range of assumed NH3 uptake coefficients (10−3–10−5). Our results show that uptake of NH3 by SOA leads to a decrease in gas‐phase NH3 mixing ratio, by as much as 27.5% and 19.0% for the highest uptake coefficient scenario (10−3) in summer and winter, respectively. The largest reduction of ammonia occurs over the Sichuan Basin and the North China Plain. The reduction of gas‐phase NH3 engenders a decrease of ammonium nitrate, by up to 30%, but has little impact on the ammonium sulfate concentration. Uptake of NH3 does not significantly affect SOA concentrations owing to overall moderate changes in aerosol acidity, and thus small effects on SOA formation from isoprene. Altogether, NH3 uptake led to a reduction in the average PM2.5 concentration up to 8.9% and 8.7% for the highest uptake coefficient (10−3) in summer and winter, respectively. These results highlight the need for better constraints on the NH3‐SOA interactions.

Phenanthroline-Catalyzed Stereoselective Formation of α-1,2-cis 2-Deoxy-2-Fluoro Glycosides.

Phenanthroline is a heterocyclic aromatic organic compound and commonly used in coordination chemistry acting as a bidentate ligand. The C4 and C7 positions of phenanthroline can often be substituted to change the binding capabilities of the ligand. Recently, there has been a push in the field of chemistry to create environmental-friendly chemical methodologies by utilizing catalysts and minimizing solvent. Herein, we have illustrated how, at high concentrations with minimal use of solvent, the C4 and C7 positions of phenanthroline can be tuned to develop an efficient and stereoselective catalyst for the formation of α-1,2-cis-fluorinated glycosides. By activating 2-deoxy-2-fluoro glycosyl halides with phenanthroline-based catalysts, we have been able to achieve glycosylations with high levels of α-selectivities and moderate to high yields. The catalytic system has been applied to several glycosyl halide electrophiles with a range of glycosyl nucleophilic acceptors. The proposed mechanism for this catalytic glycosylation system has been investigated by density functional theory calculations, indicating that the double SN2 displacement pathways with phenanthroline catalysts have lower barriers and ensure stereoselective formation of α-1,2-cis-2-fluoro glycosides.

Высокотемпературная коррозия сталей в растворах кислот. Ч. 3. Ингибиторная защита сталей азотсодержащими гетероциклическими органическими соединениями и неорганическими окислителями. Обзор

The literature and patent data on the protection of steels in high-temperature acid solutions by nitrogen-containing heterocyclic organic compounds and inhibitors of oxidative type were summarized. Composite inhibitors based on substituted triazoles can provide effective protection of low-carbon and chromium-nickel steels in these environments (200 °С). The mechanism of the protective action of these inhibitors is based on the ability of substituted triazoles to form on the steel surface in acid solutions the protective layers chemically bonded to the metal surface. Often these protective layers are basically composed of a polymer complex compound containing triazole molecules and Fe cations (in the case of nickel-chromium steels — Ni and Cr). It is noted that oxidizing additives can be used to protect steels which are in high-temperature acidic media at a passive state. Using the example of corrosion of chromium-nickel steel in H3PO4 solutions (130 °C), it is shown that additives of oxidants (Cu(II) and NO3–) stabilize the passive state of the metal in this medium, preventing the possibility of its active dissolution. Based on analysis of the literature data, a conclusion was made about the prospects of using compositions based on nitrogen-containing heterocyclic compounds for protecting steels in high-temperature acidic environments. These compositions are superior in important technological parameters to mixed inhibitors based on unsaturated organic compounds.

Structure Activity Relationship of Key Heterocyclic Anti-Angiogenic Leads of Promising Potential in the Fight against Cancer.

Pathological angiogenesis is a hallmark of cancer; accordingly, a number of anticancer FDA-approved drugs act by inhibiting angiogenesis via different mechanisms. However, the development process of the most potent anti-angiogenics has met various hurdles including redundancy, multiplicity, and development of compensatory mechanisms by which blood vessels are remodeled. Moreover, identification of broad-spectrum anti-angiogenesis targets is proved to be required to enhance the efficacy of the anti-angiogenesis drugs. In this perspective, a proper understanding of the structure activity relationship (SAR) of the recent anti-angiogenics is required. Various anti-angiogenic classes have been developed over the years; among them, the heterocyclic organic compounds come to the fore as the most promising, with several drugs approved by the FDA. In this review, we discuss the structure–activity relationship of some promising potent heterocyclic anti-angiogenic leads. For each lead, a molecular modelling was also carried out in order to correlate its SAR and specificity to the active site. Furthermore, an in silico pharmacokinetics study for some representative leads was presented. Summarizing, new insights for further improvement for each lead have been reviewed.

Effects of carbon nanomaterials on the migration and fate of organic pollutants in the ecological environment

The purpose of this study was to investigate the mechanism of adsorption reaction between heterocyclic organic compounds with different number of ring atoms and different atoms replacing carbon atoms and carbon nanotubes with different surface functional groups. Based on the current situation of research on adsorption of carbon nanomaterials adsorbing organic pollutants, the existing problems and limitations were analyzed by studying the properties and characterization of single-walled carbon nanotubes, oxidized single-walled carbon nanotubes and non-porous graphite powder, such as elemental analysis, transmission electron micrograph, zero charge point, etc. The three adsorption materials were investigated by batch experiment. Six compounds of thiophene, pyrimidine, benzene, aniline, 2-aminopyrimidine and 4,6-diaminopyrimidine were selected as the adsorbate for detecting adsorption capacity. The results showed that the affinity of different adsorbents on different adsorbents varied greatly. The adsorption capacity of heterocyclic compounds containing N and S was greatly enhanced by non-hydrophobic action. And the degree of oxidation of the adsorbent and the ph of the solution determined the adsorption capacity of the adsorbent for nitrogen-containing heterocyclic compounds. Therefore, in the ecological environment, the migration of hydrophilic organic pollutants in the environment can be reduced by the preparation of appropriate carbon nanotubes.

Construction of magnetic BiOBr@Fe3O4 hybrid nanoparticles via a sol-gel route for photocatalysis application

Development of a highly active visible-light-driven and magnetically recyclable photocatalyst is a challenge for chemical use of solar energy. In this study, Fe3O4 nanoparticles (NP), BiOBr and a superior magnetic separable BiOBr@Fe3O4 hybrid material have been synthesized via a facile chemical method. The structures, morphological, optical and physical properties of as-synthesized samples have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier transforminfrared (FT-IR) spectroscopy, photoluminescence (PL) spectroscopy. The photocatalytic activity of the as-synthesized materials is evaluated by photocatalytic degradation of aromatic, heterocyclic organic compound such as methylene blue (MB) and 85% of MB could be removed by BiOBr@Fe3O4 hybrid within 60 min. It is found that the composite yield a significantly larger amount of hydroxyl radicals through free radical scavenging test. It is proposed that the observed synergistic effect between Fe3O4 and BiOBr is due to the charge transfer between the two oxides, improving the separation of the photogenerated charge carriers via the Z-scheme mechanism, and thus accelerating the photocatalytic degradation of MB and leading to high photocatalytic stability of BiOBr@Fe3O4 material.

Synthesis and Biological Activity of 6-Substituted Pyrimidine-2,4- Dionesderivatives

Cancer is a terrible disease and second leading cause of death, behind cardio-vascular disease in the world. At present, there are three main methods of cancer treatment: surgery, radiation therapy and chemotherapy. Pyrimidineis a six-membered heterocyclic aromatic organic compound containing two nitrogen atoms at positions 1 and 3. Pyrimidine derivatives occupy a distinct and unique place in chemotherapy. The chemotherapeutic efficacy of pyrimidine derivatives is related to their ability to inhibit vital enzymes responsible for DNA biosynthesis as dihydrofolatereductase (DHFR), thymidylatesynthetase (TSase), thymidine phosphorylase (TPase) and reverse transcriptase (RTase). In the present study involves synthesis of 6-Substituted pyrimidine 2,4-diones derivatives. The synthesized compounds were subjected to antimicrobial activity against Gram negative E. coli (MTCC 40) and S. aureus (MTCC 87). The synthesized compounds possessed good to moderate antibacterial activity. Compounds 1, 2, 3a possessed good antibacterial activity when compared with standard however the compounds 2a, 2b, 2d, 1b, 1d, 1e possessed moderate activity. 1c, 1d, 1a, 2e, 2c were observed to be totally inactive compounds. The derivatives with electron withdrawing substituent on the phenyl ring at para position had poor activity in comparison to derivatives possessing no or electron donating substituents. The structures of the synthesized compounds were established by IR and NMR spectral studies.

Removal of selected heterocyclic organic compounds from water and possibilities of system optimization

Removal of selected heterocyclic organic compounds from water and possibilities of system optimization

Structural analysis of metal chelation of the metalloproteinase thermolysin by 1,10-phenanthroline

Metalloproteases and their inhibitors are important in numerous fundamental biochemical phenomena and medical applications. The heterocyclic organic compound, 1,10-phenanthroline, forms a complex with transition metal ions and is a Zn2+-chelating metalloprotease inhibitor; however, the mechanism of 1,10-phenanthroline-based chelation inhibition has not been fully elucidated. This study aimed to understand the structural basis of zinc metalloproteinase inhibition by 1,10-phenanthroline. Herein, the crystal structure of thermolysin was determined in the absence and presence of 1,10-phenanthroline at 1.5 and 1.8 Å, respectively. In native thermolysin, Zn2+ at the active site is tetrahedrally coordinated by His142, His146, Glu166, and water molecule and contains three Ca2+ ions, which are involved in thermostability. In the crystal structure of 1,10-phenanthroline-treated thermolysin crystal, seven 1,10-phenanthroline molecules were observed on the surface of thermolysin. These molecules are stabilized by π- π stacking interactions with aromatic amino acids (Phe63, Tyr66, Tyr110, His216, and Try251) or between the 1,10-phenanthrolines. Moreover, interactions with Ser5 and Arg101 were also observed. In this structure, Zn2+ at the active site was completely chelated, but no large conformational changes were observed in Zn2+ coordination with amino acid residues. Ca2+ at the Ca3 site exposed to the solvent was chelated by 1,10-phenanthroline, resulting in a conformational change in the side chain of Asp56 and Gln61. Based on the surface structure, for 1,10-phenanthroline to chelate a metal, it is important that the metal is exposed on the protein surface and that there is no steric hindrance impairing 1,10-phenanthroline access by the amino acids around the metal.

Biological Importance of Oxazoles

ing five and six member rings having hetero atoms such as N, O, S, P, Si and B etc. Many heterocyclic compounds are employed in the treatment of infectious diseases due to their specific antimicrobial activity. Heterocyclic compounds have attracted the attention of medicinal chemists because of having broad spectrum of pharmacological activities and hence it continues to yield new therapeutic agents. One such medicinal important heterocyclic nucleus is oxadiazole moiety. Oxazole is the parent compound for a vast class of heterocyclic aromatic organic compounds. These are azoles with an oxygen and a nitrogen separated by one carbon Oxazoles are aromatic compounds but less so than the thiazoles. Oxazole is a weak base

Electrolytic Oxidation of 1,8-Diazabicyclo[5.4.0]undec-7-ene in Hot-Compressed Water on a Titanium Electrode

The nitrogen-containing heterocyclic organic compound, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), was chosen to prepare a model solution to represent nitrogen-containing industrial waste streams. A ...