Imidazoline Derivatives Research Articles

Alpha‐2 Adrenergic Receptor Homology Models using Rhodopsin or Beta‐2 Adrenergic Receptor Templates

Alpha‐2 adrenergic receptor agonists are used as adjuncts to general anesthetics and in the pharmacological treatment of many disorders, including hypertension and attention‐deficit hyperactivity disorder. Clinically available alpha‐2 agonists are not subtype‐selective and their use is limited by adverse effects resulting from actions at non‐targeted subtypes. To develop subtype‐selective ligands for alpha‐2A, ‐2B, or ‐2C receptors, more binding site structural information is needed; however, the only high‐resolution crystal structures of GPCRs are of bovine rhodopsin and modified human beta‐2 and turkey beta‐1 adrenergic receptors. Our goal was to develop homology models of the alpha‐2 receptor subtypes, using either the rhodopsin or beta‐2 receptor crystal structure as a template, that are capable of identifying characteristics important in ligand binding. Alpha‐2A and ‐2C amino acid sequences were each aligned with each template sequence and homology models were created using Sybyl7.1. Fifteen alpha‐2 agonists, including catecholamines and imidazoline derivatives, were docked into the models using FlexiDock. A comparison of calculated binding energies with experimental binding affinities resulted in poor correlations in models of alpha‐2A (r2 = 0.396 and 0.606 for rhodopsin‐ and beta‐2‐based, respectively) and alpha‐2C (r2 = 0.349 and 0.338).Supported by a gift from Procter and Gamble.

2-(4,5-Dihydro-1H-imidazol-2-yl)pyridine

In the mol­ecule of the title compound, C8H9N3, a new imidazoline derivative, the six- and five-membered rings are slightly twisted away from each other, forming a dihedral angle of 7.96 (15)°. In the crystal structure, neighbouring mol­ecules are linked together by inter­molecular N—H⋯N hydrogen bonds into extended one-dimensional chains along the a axis. The pyridine N atom is in close proximity to a carbon-bound H atom of the imidazoline ring, with an H⋯N distance of 2.70 Å, which is slightly shorter than the sum of the van der Waals radii of these atoms (2.75 Å). The crystal structure is further stabilized by inter­molecular C—H⋯π and π–π inter­actions (centroid-to-centroid distance 3.853 Å).

Synergistic inhibition behaviour of methylbenzyl quaternary imidazoline derivative and iodide ions on mild steel in H 2SO 4 solutions

The inhibition behaviour of 2-undecyl-1-ethylamino-1-methylbenzyl quaternary imidazoline (2UMQI) and KI on mild steel in 1.0 M H 2SO 4 solutions was investigated at 25 °C using electrochemical methods. The results indicated that 2UMQI inhibited the corrosion of mild steel and the extent of inhibition increased with 2UMQI concentrations. The inhibition action in the presence of 2UMQI is due to physical adsorption of 2UMQI. A mixed-inhibition mechanism is proposed for the inhibitive effects of 2UMQI. Inhibition efficiency of 2UMQI was enhanced by the addition of iodide ions. In the presence of KI, the potentials of unpolarization, E u was observed and increased with KI concentration.

Discovery of substituted 2,4,4-triarylimidazoline derivatives as potent and selective neuropeptide Y Y5 receptor antagonists

Novel imidazoline derivatives were discovered to be potent neuropeptide Y Y5 receptor antagonists. High-throughput screening of Merck sample collections against the human Y5 receptor resulted in the identification of 2,4,4-triphenylimidazoline ( 1), which had an IC 50 of 54 nM. Subsequent optimization led to the identification of several potent derivatives.

Corrosion inhibition of mild steel by ethylamino imidazoline derivative in CO 2-saturated solution

The corrosion inhibition and adsorption behaviour of 2-undecyl-1-ethylamino imidazoline (2UEI) on N80 mild steel in CO 2-saturated 3% NaCl solutions was investigated using potentiodynamic polarization, electrochemical impedance spectroscopy techniques and SEM observation. Inhibitor efficiency increased with increase in 2UEI concentration. Temperature studies revealed an increase in inhibition efficiency with rise in temperature and corrosion activation energies decreased in the presence of 2UEI. A mechanism of chemical adsorption of 2UEI on the metal’s surface is proposed. The adsorption characteristics of the inhibitor were approximated by Temkin isotherm. The inhibition efficiency of 2UEI was enhanced in the presence of iodide ions.

The inhibition of CO 2 corrosion of N80 mild steel in single liquid phase and liquid/particle two-phase flow by aminoethyl imidazoline derivatives

The inhibitory behaviour of 2-undecyl-1-aminoethyl imidazoline (AEI-11) and 2-undecyl-1-aminoethyl-1-hydroxyethyl quaternary imidazoline (AQI-11) on CO 2 corrosion of N80 mild steel in single liquid phase and liquid/particle two-phase flow was investigated using weight loss, linear polarization, potentiodynamic polarization, EIS methods and SEM observations. The two compounds inhibited the CO 2 corrosion of N80 steel and the extent of inhibition was dependent on the flow conditions and particulate content. In both phases, AQI-11 exhibited better inhibition ability than AEI-11 due to the polycentric adsorption sites on its structure. Theoretical calculation on the inhibition abilities of the compounds and their modes of adsorption are reported.

QSAR study of selective I1-imidazoline receptor ligands

Selective imidazoline1-receptor (I1-R) ligands are used clinically to reduce blood pressure. Thus, there is significant interest in developing new imidazoline analogs with high selectivity and affinity for I1 receptors. A quantitative structure–activity relationship (QSAR) study was carried out on 11 potent I1-R ligands (derivatives of imidazoline, oxazoline and pyrroline) using a multiple linear regression (MLR) procedure. The selected compounds have been studied using B3LYP/3–21G(d, p) and B3LYP/6–31G(d, p) methods. Among the 42 descriptors that were considered in generating the QSAR model, three descriptors (partial atomic charges of nitrogen in the heterocyclic moiety (N-2 charge), log D and the dipole moment of the ligands) resulted in a statistically significant model with r 2 > 0.874 and > 0.802. The QSAR models were validated through cross-validation and external test set prediction. The aim of the developed MLR models for the I1-R ligands was to link the structures to their reported I1-R binding affinity log(1/Ki). The proposed QSAR models indicate that an increase in log D and the dipole moment value and a decrease in N-2 charge in the heterocyclic moiety are predictors of better selectivity and affinity for I1 receptors. The developed QSAR model is intended to predict the I1-R binding affinity of related compounds and aid in the rational design of new potent and selective I1-R ligands.

QSAR and Molecular Design of Imidazoline Derivatives as Corrosion Inhibitors

QSAR and Molecular Design of Imidazoline Derivatives as Corrosion Inhibitors

New analogues of agmatine with higher affinity to imidazoline receptors

Compilation of agmatine structure and imidazoline ring leads to a new family of imidazoline/α 2-adrenoceptor ligands, 4(5)-(2-aminoethyl)imidazoline derivatives. Constraining of the guanidine moiety into heterocyclic ring improved the affinities of the resultant fusion compounds in comparison to agmatine itself. In this work, the synthetic approach and results for I 1, I 2, and α 2-adrenoceptors affinities are reported.

Evidence that some imidazoline derivatives inhibit peripherally the vasopressor sympathetic outflow in pithed rats

Imidazoline derivatives (e.g. clonidine and moxonidine) and α 2-adrenoceptor agonists (e.g. B-HT 933) have been shown to inhibit sympathetically-induced [ 3H]noradrenaline release in several isolated blood vessels. The present study has compared the potential capability of agonists at imidazoline I 1/2 receptors and/or α 1/2-adrenoceptors to inhibit the sympathetically-induced vasopressor responses in pithed rats. For this purpose, male Wistar rats were pithed and prepared for measurement of diastolic blood pressure and heart rate. Then, the vasopressor responses induced by either selective electrical stimulation (2 ms, 60 V; 0.03, 0.1, 0.3, 1 and 3 Hz) of the vascular sympathetic outflow (T 7–T 9) or i.v. bolus injections of exogenous noradrenaline (0.03, 0.1, 0.3, 1 and 3 μg/kg) were determined before and during i.v. continuous infusions of the agonists B-HT 933 (α 2), clonidine (α 2, I 1), moxonidine (α 2, I 1), cirazoline (α 1, I 2), agmatine (putative endogenous ligand of imidazoline receptors) and methoxamine (α 1), or equivalent volumes of physiological saline. Electrical sympathetic stimulation elicited frequency-dependent vasopressor responses which were significantly inhibited during the continuous infusions of B-HT 933, clonidine, moxonidine, cirazoline and agmatine, but not of physiological saline. Interestingly, the vasopressor responses to exogenous noradrenaline, which remained unaffected during the infusions of physiological saline, B-HT 933, moxonidine, cirazoline and agmatine, were significantly blocked during the infusions of clonidine or methoxamine. These results suggest that B-HT 933, moxonidine, cirazoline and agmatine induced a prejunctional inhibition of the vasopressor sympathetic outflow in pithed rats, whilst clonidine inhibited the vasopressor sympathetic outflow by both prejunctional and postjunctional mechanisms.

Chiral palladium-pincer complex catalyzed asymmetric condensation of sulfonimines and isocyanoacetate

The asymmetric condensation of isocyanoacetate and sulfonimines was studied. Chiral BINOL and biphenantrol-based palladium-pincer complexes proved to be efficient catalysts affording 2-imidazoline derivatives with up to 86% ee. The level of enantioselectivity was clearly dependent on the γ-substituents of the BINOL ring. The best results were obtained by using biphenantrol-based pincer-complex catalysts. Some of the complexes induced the selective formation of the anti-diastereomer of the 2-imidazoline. The diastereo- and enantioselectivity showed an interesting solvent dependence as well. It was found that the application of diglyme as a solvent instead of THF leads to preferential formation of the anti product with a slight decrease of the enantioselectivity.

Molecular dynamics and density functional theory study on relationship between structure of imidazoline derivatives and inhibition performance

The inhibition performance of two imidazoline derivatives, 3-ethylamino-2-undecyl imidazoline (EUI) and chloride-3-ethylamino-3-(2,3-two hydroxyl) propyl-2-undecyl imidazoline sodium phosphate(CEPIP), for Q235 steel in CO 2 saturated solution at 298 K have been tested by weight loss experiment and electrochemical techniques. The adsorption behavior of the two inhibitors on Fe surface has been studied using molecular dynamics (MD) method and density functional theory. The results indicated that the two imidazoline derivatives could both adsorb on the Fe surface firmly through the imidazoline ring and heteroatoms, the two inhibitors both have excellent corrosion inhibition performance.

Fate and effects of amphoteric surfactants in the aquatic environment

Amphoteric surfactants form part of specialty surfactants available for formulators to improve or design new formulations in response to environmental, toxicity, safety and performance demands. Nevertheless, limited information on the ecological properties of amphoterics is available. In the present work, the aerobic and anaerobic biodegradability and the aquatic toxicity of different types of amphoteric surfactants (three alkyl betaines, one alkylamido betaine and three alkyl imidazoline derivatives) were studied. The amphoteric surfactants tested were readily biodegradable under aerobic conditions (CO 2 headspace test) and alkylamido betaines and alkyl imidazoline derivatives were also easily biodegradable under anaerobic conditions (test based on the ECETOC method). Toxicity to Photobacterium phosphoreum and Daphnia magna increased with the fatty chain length of the surfactant. The EC 50 toxicity values of the amphoterics tested were higher than 5 mg/L, and alkyl imidazoline derivatives, with EC 50 values from 20 to > 200 mg/L, showed the lowest aquatic toxicity.

Inhibition Mechanismof Imidazoline Derivative Inhibitor for Q235 Steel in Saltwater Saturated with CO<SUB>2</SUB>

Inhibition Mechanismof Imidazoline Derivative Inhibitor for Q235 Steel in Saltwater Saturated with CO<SUB>2</SUB>

The Synthesis of Imidazoline Derivative Compounds as Corrosion Inhibitor towards Carbon Steel in 1% NaCl Solution

Oleic imidazoline is one of the nitrogen containing heterocyclic compounds that has been widely used as commercial corrosion inhibitor, especially in minimizing the carbon dioxide induced corrosion process in oilfield mining. In this present work, some imidazoline derivative compounds have been synthesized utilizing both conventional and microwave assisted organic synthesis (MAOS) methods, in order to determine their corrosion inhibition properties on carbon steel surface. The MAOS method is more effective in synthesizing these compounds than the conventional method regarding to the higher chemical yields of products (91% to 94%) and the shorter reaction times (7 to 10 minutes). The characterization of corrosion inhibition activities of the synthesized products towards carbon steel in 1% NaCl solution was determined by the Tafel plot method. The corrosion inhibition activities of compound 1b ((Z)-2-(2-(heptadec- 8-enyl)-4,5-dihydroimidazol-1-yl)ethanamine), 2b ((Z)-2-(2-(heptadec-8-enyl)- 4,5-dihydroimidazol-1-yl)ethanol) and 3b (2-(2-heptadecyl-4,5-dihydroimidazol- 1-yl)ethanamine) at 8 ppm concentration in 1% NaCl solution are, respectively, 32.18%, 39.59% and 12.73%. The heptadec-8-enyl and hydroxyethyl substituents at C(2) and N(1) position of imidazoline ring, respectively, gave the most effective corrosion inhibition activity towards carbon steel compared to the presence of other substituents. The increase in concentrations of compound 1b, 2b and 3b in 1% NaCl solution tends to improve their corrosion inhibition activities. Based on the analysis of the free Gibbs adsorption energy (ΔG 0 ads) values of compound 1b, 2b and 3b (-32.97, -34.34 and -31.27 kJ/mol, respectively), these compounds have the potential to interact with carbon steel through semi-physiosorption or semi-chemisorption.

Palladium Pincer Complex‐Catalyzed Condensation of Sulfonimines and Isocyanoacetate to Imidazoline Derivatives. Dependence of the Stereoselectivity on the Ligand Effects

AbstractPalladium‐catalyzed condensation reactions of sulfonimines with isocyanoacetate were performed using various PCP, SCS, SeCSe and NCN pincer complexes as catalysts. The reactions proceeded rapidly (2 h) at room temperature using only 1 mol % pincer complex catalyst without any additives. The electron‐deficient and relatively bulky PCP complex provides imidazoline derivatives with a very high syn diastereoselectivity. The applied PCP catalyst proved to be very robust under the applied reaction conditions, as it could be recovered without any decomposition after the completed catalytic process. The stereoselectivity of the condensation reactions is reversed by employing the electron‐rich SeCSe type of complexes. Simple palladium salts, such as palladium acetate, Pd(OAc)2, catalyze the reaction with a poor stereoselectivity. The stereoselectivity of the PCP complex‐catalyzed process does not depend significantly on the steric bulk of the sulfonimine component. Mechanistic studies revealed that the PCP complex‐catalyzed reaction proceeds via an η1‐coordinated palladium isocyanoacetate pincer intermediate. This intermediate could also be isolated and its structure was determined by X‐ray diffraction. The X‐ray structure of this reaction intermediate indicates a surprisingly strong carbon‐metal bond between the palladium atom and the coordinated isocyanoacetate molecule. Our mechanistic studies show that the pincer complex catalyst does not undergo redox reactions and, thus it retains a +2 oxidation state under the catalytic process.

A Facile Synthesis of Oxazolines, Thiazolines, and Imidazolines Using α,α‐Difluoroalkylamines.

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Corrosion inhibition of aluminium in acid solutions by some imidazoline derivatives

2-Pentadecyl-1,3-imidazoline (PDI), 2-Undecyl-1,3-imidazoline (UDI), 2-Heptadecyl-1,3-imidazoline (HDI), 2-Nonyl-1,3-imidazoline (NI) were synthesized and characterized by FT-IR and NMR Studies. The corrosion inhibition properties of these compounds on aluminium in 1 M HCl and 0.5 M H2SO4 were investigated by weight loss, potentiodynamic polarization, electrochemical impedance and scanning electron microscopic techniques. The weight loss study showed that the inhibition efficiency increases with increase in the concentration of the inhibitor and was found to be inversely related to time and temperature while it shows no significant change with increase in acid concentration. The effectiveness of these inhibitors were in the order of UDI > NI > PDI > HDI .The values of activation energy, free energy of adsorption, heat of adsorption, enthalpy of activation and entropy of activation were also calculated to elaborate the mechanism of corrosion inhibition. The adsorption of these compounds on aluminium surface follows the Langmuir adsorption isotherm. The potentiodynamic polarization data show that the compounds studied are mixed type inhibitors. Electrochemical impedance was used to investigate the mechanism of corrosion inhibition. The surface characteristics of inhibited and uninhibited metal samples were investigated by scanning electron microscopy (SEM).

Imidazole and Imidazoline Derivatives as N‐Donor Ligands for Palladium‐Catalyzed Mizoroki—Heck Reaction.

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Evaluation of inhibition efficiency of an imidazoline derivative in CO 2-containing aqueous solution

The inhibition efficiency of an imidazoline derivative for API X65 steel in CO 2-saturated 5% NaCl solution has been studied by using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements. This imidazoline derivative acts as a mixed-type inhibitor, which suppresses both cathodic and anodic processes by its adsorption on the electrode surface according to Langmuir adsorption isotherm, together with a slight positive shift in corrosion potential ( E corr). The adsorbed inhibitor on the surface of electrode affects the kinetic processes of cathodic and anodic reactions and increases the reaction activation energy. Both potentiodynamic polarization and EIS measurements reveal that this imidazoline derivative inhibits the corrosion of API X65 steel in CO 2-saturated 5% NaCl solution and that the inhibition efficiency increases with increasing of the inhibitor concentration. The Nyquist plot of uninhibited electrode at E corr is characterized by a depressed semicircle from high to medium frequencies and an inductive loop at low frequencies while the inhibited ones emerge “degradation” phenomena with simple depressed capacitive loops. The semicircles representing the inhibitor film merge with the charge transfer loops. The inhibitor films form gradually and the inhibition efficiency increases with increase of immersion time.