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The corrosion behavior of Al in 1 M HCl solution with and without thiophene derivatives is studied utilizing altered chemical and electrochemical methods. Thiophene derivatives have been prepared and characterized by infrared (IR), proton nuclear magnetic resonance (1H NMR) and mass spectral studies. The corrosion data were obtained using weight reduction and electrochemical techniques. The outcome data revealed that the efficiency rises with improving the dose of thiophene derivatives in aggressive solution, while it lowered with the rise of temperature. The adsorption of the studied thiophene derivatives on the surface of Al follows Langmuir isotherm. The thermodynamic parameters such as adsorption constant Kads and free energy of adsorption ( $$\Delta G_{{{\text{ads}}}}^{^\circ }$$ ) are calculated and discussed. Polarization curves indicated that the thiophene derivatives are mixed-kind inhibitors. The quantum calculation such as EHOMO, ELUMO and ΔE were obtained and related to the experimental data. The biological effect of these derivatives also discussed.

A photo-active gellan gum (Gel) derivative was developed by amide bond combination with trans-4-[p-(amino)styryl]pyridine (SP). The SP-Gel was cross-linked by UV curing via the intermolecular 2π + 2π cycloaddition of the inserted SP–CH=CH- moieties. The chemical structure of the obtained photo-crosslinkable biopolymer was investigated before and after the UV curing and the progress of the performed 2π + 2π cycloaddition-based cross-linking was detected via UV–visible light spectra. SP-Gel was evaluated as a polymeric matrix for the immobilization of catalase via entrapment technique. The synthesized biopolymer was mixed with the catalase and molded in the form of membranes that were UV cured to encapsulate the enzyme. The membranes were able to entrap 0.75 mg/cm2 with retained activity reached above 95%. The immobilized catalase displayed higher thermal stability and higher resistance toward the environmental pH disturbances compared to the free enzyme. Also, despite the observed lower catalase-H2O2 affinity upon the entrapment that was indicated from the performed kinetic studies, the reusability and storage stability experiments revealed the economic value of the entire process by preserving around 95% and 83% of the initial catalase activity after the fifth and tenth operation cycles, respectively.

Heterocycles incorporating a pyrimidopyrimidine scaffold have aroused great interest from researchers in the field of medical chemistry because of their privileged biological activities; they are used as anti-bacterial, antiviral, anti-tumor, anti-allergic, antihypertensive, anticancer, and hepatoprotective agents. Therefore, the present study aims to investigate the chemistry of heterocycles incorporating pyrimido[1,6-a]pyrimidine and pyrimido[1,6-c]pyrimidine skeletons and their biological characteristics. The main sections discuss (1) the synthetic routes to obtain substituted pyrimidopyrimidines, pyrimido[1,6-a]pyrimidin-diones, pyrimidoquinazolines, tricyclic, tetracyclic, and binary systems; (2) the reactivity of the substituents attached to the pyrimidopyrimidine skeleton, including thione and amide groups, nucleophilic substitutions, condensations, ring transformations, and coordination chemistry; (3) compounds of this class of heterocycles containing a significant characteristic scaffold and possessing a wide range of biological characteristics.

The present review highlights the synthetic procedures reported for the preparation of oxazolo[3,2-a]pyridines as a class of 5-6 bicyclic heterocycles with a nitrogen atom at the ring junction. The...

The present study provides an overview of the chemistry and biological significance of pyrimido[4,5-d]pyrimidine and pyrimido[5,4-d]pyrimidine analogs as types of bicyclic [6 + 6] systems. The main sections include: (1) synthesis methods; (2) the reactivities of the substituents linked to the ring carbon and nitrogen atoms; and (3) biological applications. A discussion demonstrating the proposed mechanisms of unexpected synthetic routes is intended. The aim of this study is to discuss the synthetic significance of the titled compounds and to establish the biological characteristics of this class of compounds as studied to date, where the compounds have been applied on a large scale in the medical and pharmaceutical fields. This survey will help researchers in the fields of synthetic organic and medicinal chemistry to undertake and improve new approaches for the construction of new standard biological components.

This review describes the chemistry of 2,3-dihydroxynaphthalene and the related analogues. The synthetic routes reported to obtain the investigated structures are discussed. In addition, the reacti...

4-Formylphenyl benzoate was utilized as a versatile precursor for the construction of new series of heterocyclic scaffolds that contain thiazole and thiazolidin-5-one rings. The antibacterial activity of these scaffolds against two types of bacteria was screened and most of them exhibited good activity. Among the synthesized thiazole derivatives, compounds 5, 6, and 8a showed antibacterial activity close to the standard chemotherapeutic (Ampicillin).

An enantio-selective l -histidine imprinted polymeric resin was fabricated and evaluated for enantiomeric resolution of histidine racemate. The polymerizable chiral salicyloyl- l -histidine amide was first synthesized and anchored onto a polymeric resin network via condensation polymerization with resorcinol and formaldehyde. l -histidine template molecules were then extracted out of the resin texture via alkaline hydrolysis of the amide bond using sodium hydroxide. The synthetic steps were monitored by means of instrumental techniques including elemental analysis; mass spectra along with both Fourier transform infrared and nuclear magnetic resonance spectroscopy. In addition, the surface morphologies of both imprinted and non-imprinted resins were visualized using scanning electron microscope and the images indicated a relatively rougher surface in case of the imprinted resin. Also, the complete extraction of the template l -histidine molecules was assured using energy-dispersive X-ray spectroscopy, which indicated the absence of nitrogen upon alkaline treatment of the synthesized l -histidine containing resin. Selective adsorption experiments indicated that the maximum adsorption was achieved at pH 8 and followed the pseudo-second-order kinetic model with extracted amounts of 165 ± 1 and 90 ± 1 mg/g with respect to l - and D-histidine, respectively. Moreover, Langmuir model displayed the best fit with the experimentally obtained isotherm data and the maximum adsorption capacities were 195 ± 1 and 102 ± 1 mg/g with respect to l - and d - histidine, respectively. The enantiomeric resolution of d / l -histidine racemate was also carried out utilizing a column backed with the imprinted resin and the outlet collected solution displayed an optical activity related to 36% d -histidine enantiomeric excess.

In a continuation of our program to develop a new class of antimicrobial and antioxidant agents, 13 novel 3-substituted indole derivatives incorporating biologically active heterocycles were synthesized and evaluated for their in vitro antimicrobial activity. Among the synthesized compounds, 3-(7H-imidazo[2,1-c][1,2,4]triazol-5-yl)-1H-indole showed activity against E. faecalis equal to that of ampicillin and 50% higher activity than ampicillin against S. aureus and B. subtilis. Also, 3-(7H-imidazo[2,1-c][1,2,4]triazol-5-yl)-1H-indole was found to exhibit strong in vitro antifungal activity against Candida albicans, Aspergillus niger, and Penicillium sp. The antioxidant activity of the obtained indole derivatives was also studied using 2,2'-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid).

This review described the synthetic methods, chemical reactivity and biological applications of furan carboxamide compounds. Furan-carboxamides are reported to have important and variable biologica...

The present study provides an overview of the chemistry and biological significance of pyrimido[4,5

The versatile hitherto reported 3-(1H-indol-3-yl)-1H-pyrazol-5-amine () was synthesized by the reaction of 3-cyanoacetylindole () with hydrazine hydrate in refluxing ethanol and used as a key intermediate for the synthesis of novel pyrazolo[1,5-a]pyrimidines via its reactions with appropriate 1,3-biselectrophilic reagents or through three-component condensations with triethyl orthoformate and compounds possessing an activated methylene group. Besides, the applicability and synthetic potency of () to attain polyfunctionally substituted imidazo[1,2-b]pyrazole, pyrazolo[1,5-a][1,3]diazepine and pyrazolo[1,5-c][1,3,5]thiadiazine derivatives of an expected pharmaceutical interest have been investigated. The mechanistic aspects for the formation of the newly synthesized compounds are discussed.

This review describes a literature survey of 1,3,5-triazepines. The investigated heterocycles were the monocyclic and fused 1,3,5-triazepines. The different sections of the paper cover: theoretical methods, spectroscopy aspects, thermodynamic aspects, synthesis and reactions of the monocyclic and fused heterocycles incorporated into the 1,3,5-triazepine moiety. The biological evaluation of the target compounds are also described as well as their synthetic applications. The reaction mechanisms are discussed.

4-(Thiazol-2-yldiazenyl)-1H-pyrazole-3,5-diamine (2) was prepared by the reaction of 2-thiazolylazomalononitrile (1) with hydrazine hydrate in boiling ethanol and used as key intermediate for the synthesis of polyfunctionally substituted pyrazolo[1,5-a]pyrimidines via its reactions with reagents having 1,3-dielectrophilic centers. Structures of the newly synthesized compounds were established by elemental analysis and spectral data. Representative compounds of the synthesized products were tested and evaluated as antioxidant agents. The results revealed that compounds (3), (4), (5), and (9) displayed promising antioxidant activity compared to the activity of ascorbic acid.

2-Thiazolylhydrazonomalononitrile (1) was used as key intermediate for the synthesis of polyfunctionally substituted heterocycles (e.g. pyridazine, tetrazole, pyrimidines, 1,5-benzo diazepine, benzoimidazo[1,2-a]pyrimidine, triazolo[4,3-a]pyrimidine, pyrazole, pyrazolo[1,5-a]triazines, pyrazolo[1,5-a]pyrimidine and 1,5-benzoxazocine) incorporating thiazole moiety via its reactions with some carbon and nitrogen nucleophiles. Structures of the newly synthesized compounds were established by elemental analysis and spectral data. The mechanistic aspects for the formation of the new compounds were also discussed.

3-(1H-Indol-3-yl)-1H-pyrazol-5-amine 3 was prepared in a quantitative yield by heating 3-(1H-indol-3-yl)-3-oxopropanenitrile 2 in dry ethanol with hydrazine hydrate, and utilized as key intermediate for the synthesis of some new pyrazolo[1,5-a]pyrimidines and pyrazolo[5,1-c]triazines. Structures of the newly synthesized compounds were established by elemental analysis and spectral data and evaluated as antioxidant agents. Most of the tested compounds belonging to the pyrazolo[1,5-a]pyrimidine series exhibited better activities than members of the pyrazolotriazine one.

2-(4-Oxo-1-phenyl-4,5-dihydro-1H-pyrazolo[3,4-d]pyrimidin-6-yl)acetonitrile was used as the key intermediate for the synthesis of polyfunctionally substituted heterocycles (e.g., pyrazoles, pyridine, tetrazole, thiazoles, thiophenes, and chromene) incorporating the pyrazolo[3,4-d]pyrimidin-4-one moiety. Representative compounds of the synthesized series were tested and evaluated as antioxidants. Two of the tested compounds (pyrazole and thiophene derivatives) showed antioxidant activity nearly equal to that of ascorbic acid.

A novel multicomponent synthesis of highly substituted pyrazolo[1,5-a]pyrimidine derivatives starting from simple and readily available reactants is described. Three-component condensation of 4-(thiazol-2-yldiazenyl)-1H-pyrazole-3,5-diamine with triethyl orthoformate and carbonyl compounds or nitriles containing an activated methylene group gave substituted pyrazolo[1,5-a]pyrimidines. An analogous reaction of 4-(thiazol-2-yldiazenyl)-1H-pyrazole-3,5-diamine with ethyl acetoacetate and benzaldehyde in an effective one-pot process furnished ethyl 2-amino-5-methyl-7-phenyl-3-(thiazol-2-yldiazenyl)-4,7-dihydropyrazolo[1,5-a]pyrimidine-6-carboxylate.

This review highlighted the methods used for the synthesis of different heterocyclic compounds derived from 3-(1H-indol-3-yl)-3-oxopropanenitrile. The reactivity and their synthetic importance were investigated. In this context, recent progress in the synthesis and use of 3-(1H-indol-3-yl)-3-oxopropanenitrile as precursors for heterocyclic compounds is reviewed.

4-(4-oxo-4H-benzo[d][1,3]oxazin-2-yl)phenyl-4-methylbenzenesulfonate 2 was prepared and reacted with some nitrogen and sulfur nucleophiles. The prepared products were evaluated as antioxidant and corrosion inhibitors for gasoline lubricating oil in which compounds, 4-(3-amino-4-oxo-3,4-dihydroquinazolin-2-yl)phenyl-4-methylbenzene sulfonate 12, 4-(3-(3-chloro-2-oxo-4-phenylazetidin-1-yl)-4-oxo-3,4-dihydroquinazolin-2-yl)phenyl 4-methylbenzenesulfonate 14, 4-(4-oxo-3-(4-oxo-2-phenylthiazolidin-3-yl)-3,4-dihydroquinazolin-2-yl)phenyl 4-methylbenzenesulfonate 15, and 4-(3-(1,3-dioxoisoindolin-2-yl)-4-oxo-3,4-dihydroquinazolin-2-yl)phenyl 4-methylbenzenesulfonate 18 exhibited the highest antioxidant activity. It was interesting also to study the effect of concentration of additive 15 to find the optimum concentration recommended to be used, 0.1 g for 1 L oil of additive 15 was the more effective concentration to be used. Also, measurements of thermal analyses were carried out.

An enantioselective S-mandelic acid (S-MA) imprinted chitosan (SMIC) was prepared by cross-linking of chitosan using formaldehyde cross-linker, in the presence of S-MA as an imprint template molecule and 0.5% acetic acid solution as a solvent. Non-imprinted cross-linked chitosan (NIC) as control was also prepared by the same procedure in absence of template molecules. The surface morphology of both SMIC and NIC were examined by scanning electron microscope (SEM). SMIC particles were applied to determine the optimum operational condition for S-MA separation from dilute aqueous solution. In adsorption step, optimum pH and retention time were 3.5 and 60 min, while corresponding values in extraction step were 1 and 40 min, respectively. Also, the adsorption isotherms indicated that the maximum adsorption capacities of S- and R-MA on SMIC were 100 ± 0.5 and 64 ± 0.8 mg/g, respectively, while in the case of NIC, both R- and S-MA present the same maximum adsorption.

2-Thiazolylhydrazonomalononitrile (1) was used as key intermediate for the synthesis of polyfunctionally substituted heterocycles (e.g. pyridazine, tetrazole, pyrimidines, 1,5-benzo diazepine, benzoimidazo[1,2-a]pyrimidine, triazolo[4,3-a]pyrimidine, pyrazole, pyrazolo[1,5-a]triazines, pyrazolo[1,5-a]pyrimidine and 1,5-benzoxazocine) incorporating thiazole moiety via its reactions with some carbon and nitrogen nucleophiles. Structures of the newly synthesized compounds were established by elemental analysis and spectral data. The mechanistic aspects for the formation of the new compounds were also discussed.

The starting oxazolone 1 was reacted with p-aminophenol in glacial acetic acid to afford imidazolone 2, which afforded Mannich base 3 via the reaction with piperidine and paraformaldehyde. Moreover, the reaction of 2 with ethylchloroacetate or chloroacetic acid in dry acetone gave the corresponding imidazolones 4 and 5, respectively. Compound 4 reacted with benzylamine or 4-chlorobenzaldehyde to furnish 6 and 7, respectively. On the other hand, oxazolone 1 reacted with hydrazines in glacial acetic acid to afford the 1,2,4-triazines 11–15. Representative compounds of the synthesized products were established and evaluated as antioxidant and corrosion inhibitors for gasoline lube oils.

This review presents a systematic and comprehensive survey of the methods ofpreparation and the chemical reactivity of 3-(2-haloacyl)indoles. These compounds are important intermediates for the synthesis of a variety of otherwise difficult to obtain synthetically useful and novel heterocyclic systems. The data published over the past few years are reviewed here for the first time.

A novel multicomponent synthesis of highly substituted pyrazolo[1,5-a]pyrimidine derivatives starting from simple and readily available reactants is described. Three-component condensation of 4-(thiazol-2-yldiazenyl)-1H-pyrazole-3,5-diamine with triethyl orthoformate and carbonyl compounds or nitriles containing an activated methylene group gave substituted pyrazolo[1,5-a]pyrimidines. An analogous reaction of 4-(thiazol-2-yldiazenyl)-1H-pyrazole-3,5-diamine with ethyl acetoacetate and benzaldehyde in an effective one-pot process furnished ethyl 2-amino-5-methyl-7-phenyl-3-(thiazol-2-yldiazenyl)-4,7-dihydropyrazolo[1,5-a]pyrimidine-6-carboxylate.

This review describes the synthesis and reactions of 2-amino-3-carbethoxythiophenes as building blocks for the syntheses of poly functionalized heterocyclic compounds.