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Heterocyclic compounds are crucial for medicinal chemistry and the development of therapeutic agents like broad-spectrum antibiotics. This study devised a facile procedure to synthesize novel antimicrobial bicyclic heterocycles from 2-mercapto-3-phenylquinazolin-4(3H)-one. Advanced analytical techniques including 1H and 13C NMR, elemental analysis, and FT-IR spectroscopy characterized the intricate chemical structures of the products. In vitro assays tested the heterocycles against aerobic and anaerobic bacterial strains using fluconazole and ciprofloxacin as antifungal and antibacterial controls. Results demonstrated the formidable broad-spectrum antibacterial and antifungal activities of the synthesized compounds, with growth inhibition approaching that of the positive controls. These findings highlight the immense potential of these novel heterocyclic compounds as antimicrobial agents. Further research can optimize their drug-like properties for eventual clinical use in combating drug-resistant infections. [ABSTRACT FROM AUTHOR]

The process of midazolam ring closure was studied from the thermodynamic and kinetic points of view by means of quantum-chemical methods. B3LYP/6–311 + + G(d,p) model was employed for gas phase and water environment (polarizable continuum model) calculations. It was concluded that the reaction rate determining step is the first step—carbinolamine formation from amine and carbonyl ends of the opened benzodiazepine ring. The Gibbs free energy of activation was calculated as 35.1 kcal/mol for gas- phase and 33.9 kcal/mol for water environment. Intrinsic reaction coordinate calculations were performed to verify that the transition state really connects the substrate and product. Thermodynamically, this reaction is endoergic with ΔG = 9.6 kcal/mol for gas phase and 10.0 kcal/mol for water environment. However, the next step—carbinolamine protonation with immediate water molecule loss is expected to be fast and activation barrierless, which enables further progress of the ring closure, despite the positive ΔG of the fist step. Next, the protonated imine undergoes deprotonation to final closed ring, pharmacologically active molecule of midazolam. The whole chain of reaction is exoergic with ΔG equal to − 5.6 kcal/mol for gas phase and − 7.7 kcal/mol for water environment. In order to understand the role of other than benzodiazepine/imidazole molecular fragments on the ring closure process, a model was build which contains only benzodiazepine and imidazole rings. The activation barrier for the carbinolamine formation of the model is similar to midazolam in the gas phase but higher by about 10 kcal/mol for water environment. The most interesting difference is however that for the model, the carbinolamine formation step is exoergic with ΔG equal to − 2.2 kcal/mol for gas phase and − 1.8 kcal/mol for water environment. This difference can be connected to complicated conformational shape of the midazolam molecule, which during the ring closure undergoes unfavorable deformations with accompanying rise of the energy of the molecule. The protonation sites for both midazolam and the model were also studied. In the case of midazolam, the preferred protonation site is the imidazole ring nitrogen atom, but in the case of the model it is the benzodiazepine ring nitrogen atom. The aromaticity of the 5- and 7-membered rings were analyzed using two aromaticity—HOMA and pEDA. It follows that larger stability of the cation protonated at the benzodiazepine ring is accompanied with substantial increase of the 7-ring aromaticity in the model of midazolam. The complexes of midazolam and its model with a water molecule were analyzed because they are needed for evaluation of the energy of the whole process of ring closure. In the case of midazolam, the water molecule preferentially connects to imidazole ring, but in the case of the model, complexes with both imidazole and benzodiazepine rings have similar stability. [ABSTRACT FROM AUTHOR]

Benzene-1,3,5-tricarboxylic acid-functionalized MCM-41 (MCM-41-Pr-BTA), as a novel hybrid organosilica, was prepared and properly characterized by the Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller, thermal gravimetric analysis and energy-dispersive X-ray spectroscopy to evaluate the functional groups, crystallinity, surface area, morphology, particle size distribution and loading of functional groups. Interestingly, the 1,3-propylene linker used in this study incorporates appropriate catalytic activity into the MCM-41 framework compared to the more known trialkoxypropyl silanes. This new organosilica can be used as a hybrid nanocatalyst for the expeditious and efficient synthesis of 2,3-dihydroquinazolin-4(1H)-one derivatives, as an important pharmaceutical scaffold, in aqueous media via a three-component one-pot condensation of isatoic anhydride and aromatic aldehydes with primary amines or ammonium salts. This method has several advantages such as low catalyst loading, high to excellent yields, short reaction times, working under green conditions and simple workup. [ABSTRACT FROM AUTHOR]

Previously synthesized 9-aryl-5 H-imidazo[2,1- d][1,2,5]triazepin-6(7 H)-ones have been used as starting materials for the synthesis of three new tricyclic ring systems, where an imidazotriazepine is condensed with an imidazole, triazole or tetrazole ring. These novel compounds could be potential drug candidates for central nervous system diseases because of their closely related structure to known tricyclic derivatives with anticonvulsant activity. Graphical Abstract : [ABSTRACT FROM AUTHOR]

1,4-Diaryl-5 H-pyrrolo[2,1- d][1,2,5]triazepines were prepared by two different pathways. In the first case, the condensation reaction of the appropriate diketones with hydrazine monohydrate was applied for the construction of the seven-membered triazepine ring. In the second case, previously prepared intermediates, 1-aryl-3 H-pyrrolo[2,1- d][1,2,5]triazepine-4(5 H)-thiones were used as starting materials. The arylation of these thioamides were carried out with boronic acids in Liebeskind-Srogl palladium-catalysed cross-coupling reaction. Graphical abstract: [ABSTRACT FROM AUTHOR]

The results of studies aimed at producing and developing a new methodology of synthesis of functional derivatives of benzoazacrown ethers by stepwise transformation of the benzocrown macrocycle are generalized. The comprehensive study of the spatial structure and complexation properties of the starting benzocrown ethers, target benzoazacrown ethers, and their nearest structural analogs shows that the N-alkylbenzoazacrown derivatives exhibit a much higher ability to bind metal and ammonium cations compared to the corresponding N-phenylazacrown ethers. They are comparable with benzocrown ethers in complexation properties and exceed them in some cases. A new approach to the synthesis of dinitrodibenzodiazacrown ethers is proposed based on the one-step transformation of the macrocycle of the dinitrodibenzo18-crown-6 cis-isomer under the action of aliphatic diamines. The synthesis of styryl dyes containing the N-methylbenzoazacrown fragment is described. The detailed studies by electron spectroscopy, NMR spectroscopy, and X-ray diffraction analysis revealed a high potential of these dyes as optical molecular sensors for alkaline and alkaline-earth metal cations. [ABSTRACT FROM AUTHOR]

Formation of thiophene-substituted isoxazoles by reaction of chalcone dibromides and 1,3-diketones with hydroxylamine hydrochloride has been examined under different conditions. Use of KOH as base in the reaction of dibromide chalcone analogs with hydroxylamine hydrochloride yields mixtures of isomeric isoxazoles in modest yields. Replacement of KOH with pyridine affords negligible amounts of isoxazoles only, the intermediate 2-bromoprop-2-en-1-one being isolated from the reaction as the major product. Substitution of the β-bromine atom from a chalcone dibromides with a methoxy group by solvolysis occurred when no base was used. Mixtures of isomeric isoxazoles in which the isoxazole that had a 2-thienyl group at position 5 were always major components, were obtained in good yields from reaction of thiophene-containing 1,3-diketones with hydroxylamine hydrochloride, irrespective of reaction pH. At low pH, regioselectivity was poorer than that observed for reaction of chalcone dibromides with hydroxylamine hydrochloride, but yields were substantially better. At high pH, yields were comparable with those at low pH and regioselectivity for 3-aryl-5-(2-thiophenyl)isoxazole was slightly enhanced, but the dioxime corresponding to the initial 1,3-diketone was also produced in low yields as a mixture of stereoisomers. [ABSTRACT FROM AUTHOR]

Success of ring closure reactions of substrates having two terminal alkenes through olefin metathesis depends on a number of factors such as catalysts, nature and size of the rings to be formed and the substituents/functional groups present on the alkenes as well as at the allylic position. This article presents an overview of these influencing factors with illustrative examples. [ABSTRACT FROM AUTHOR]

Temperature induced conformational changes of various alkanes were studied. n-Hexane was studied in order to demonstrate its ability to be involved in C and C ring closure reactions, while long chain alkanes, such as C, C and C, were investigated with the aim to calculate their temperature dependent molecular diameter controlling their penetration ability into zeolite channels. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Monthly / Monatshefte für Chemie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chemical Monthly / Monatshefte für Chemie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chemical Monthly / Monatshefte für Chemie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Meldrum's acid ( 2) is acylated by diketen affording the acyl Meldrum's acid 3. In aqueous bicarbonate its 3-oxogroup is selectively reduced by sodium tetrahydroborate giving the alcohol 4, which readily undergoes cyclization in refluxing dioxane leading to the title pyrone 7. Under identical conditions 3 produces the pyrone 6 with the pyrone carboxylic acid 5 as intermediate. [ABSTRACT FROM AUTHOR]

4H-3,1-Benzothiazin-4-ones are accessible by various preparative routes mostly starting from anthranilic acid derivatives. These facile synthetic entries allow for the introduction of diverse substituents at positions 2 and 5–8. In this review, representative methods to generate 4H-3,1-benzothiazin-4-ones and the biological activities of the resulting products are highlighted.4H-3,1-Benzothiazin-4-ones are accessible by various preparative routes mostly starting from anthranilic acid derivatives. These facile synthetic entries allow for the introduction of diverse substituents at positions 2 and 5–8. In this review, representative methods to generate 4H-3,1-benzothiazin-4-ones and the biological activities of the resulting products are highlighted.4H-3,1-Benzothiazin-4-ones are accessible by various preparative routes mostly starting from anthranilic acid derivatives. These facile synthetic entries allow for the introduction of diverse substituents at positions 2 and 5–8. In this review, representative methods to generate 4H-3,1-benzothiazin-4-ones and the biological activities of the resulting products are highlighted.4H-3,1-Benzothiazin-4-ones are accessible by various preparative routes mostly starting from anthranilic acid derivatives. These facile synthetic entries allow for the introduction of diverse substituents at positions 2 and 5–8. In this review, representative methods to generate 4H-3,1-benzothiazin-4-ones and the biological activities of the resulting products are highlighted.4H-3,1-Benzothiazin-4-ones are accessible by various preparative routes mostly starting from anthranilic acid derivatives. These facile synthetic entries allow for the introduction of diverse substituents at positions 2 and 5–8. In this review, representative methods to generate 4H-3,1-benzothiazin-4-ones and the biological activities of the resulting products are highlighted. [ABSTRACT FROM AUTHOR]

Copyright of Chemical Monthly / Monatshefte für Chemie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)