Pyridazin-3(2H)-ones: the versatile pharmacophore of medicinal significance

Synthesis, α-Glucosidase inhibitory activity and docking studies of Novel Ethyl 1,2,3-triazol-4-ylmethylthio-5,6-diphenylpyridazine-4-carboxylate derivatives

In this work, a novel series of pyridazine-triazole hybrid molecules were prepared and evaluated as inhibitors of rat intestinal α-glucosidase enzyme. Amongst all newly synthesized compounds, 10k showed good inhibition in the series with IC₅₀ value of 1.7 µM which is 100 folds stronger than positive control, acarbose. The cytotoxicity revealed that this compound is not toxic against normal cell line, HDF. The docking studies showed that triazole ring plays an important role in the binding interactions with the active site. The insertion of compound 10k into the active pocket of α-glucosidase and formation of hydrogen bonds with Leu677 was observed from docking studies. The kinetic studies revealed that this compound has uncompetitive mode of inhibition against α-glucosidase enzyme.

Synthesis and evaluation of novel thiazole moiety-containing compounds as antibreast cancer agents

Progesterone receptor (PR) agonists represent pivotal agents in trapping breast cancer cells through modulating the expression of estrogen receptor (ER). The present investigation aimed to test three novel thiadiazole-containing compounds as antibreast cancer agents. Test compounds were synthesized and abbreviated as 2-{(5-amino-1, 3, 4-thiazole-2-yl) amino}-4-(4-chloro-3-methylphenyl)-4-oxobutanoic acid (TAB), 4-(4-chloro-3-methylphenyl)-4-oxo 2-[(5-sulfanyl-1, 3, 4-thiadiazol-2-yl)] sulfanyl-butanoic acid (TSB) and 4-(4-chloro-3-methylphenyl)-4-oxo 2-[(5-sulfanyl-1, 3, 4-thiadiazol-2-yl)] sulphonyl-botanic acid (TSSB). Molecular docking of the test compounds with PR was simulated. The IC 50 of the test compounds against both Michigan cancer foundation-7 (MCF-7) and HepG2 was determined. Ehrlich solid tumor (EST) was grown in the right thigh of the mouse as a model of breast cancer in vivo . Hepatic and renal functions, besides hematological indicators, were tested. The expression of ER and ER genes in EST was determined using real-time PCR. Immunohistochemistry was carried out for the determination of Ki-67 and cyclin-dependent kinase 1 (CDK-1) in EST. Our results revealed that TAB, TSB and TSSB reduced Ehrlich tumor size by 48, 64 and 52%, respectively, compared to the EST control group. The docking scores achieved by TAB, TSB and TSSB with PR were -9.29, -9.41 and -9.24 kcal/mol, respectively. The most potent compound against MCF-7 was TSB, with an IC 50 of 3.9 g/ml. The administration of test compounds suppressed Ki-67 and CDK1, and the best effect was observed at TSB. Our findings suggest that test compounds are applicants to be antibreast cancer agents.

A combination screening to identify enhancers of para-aminosalicylic acid against Mycobacterium tuberculosis

Para-aminosalicylic acid (PAS) is an antibiotic that was largely used for the multi-therapy of tuberculosis in the twentieth century. To try to overcome the inconvenience of its low efficacy and poor tolerance, we searched for novel chemical entities able to synergize with PAS using a combination screening against growing axenic Mycobacterium tuberculosis. The screening was performed at a sub-inhibitory concentration of PAS on a library of about 100,000 small molecules. Selected hit compounds were analyzed by dose–response and further probed with an intracellular macrophage assay. Scaffolds with potential additive effect with PAS are reported, opening interesting prospects for mechanism of action studies. We also report here evidence of a yet unknown bio-activation mechanism, involving activation of pyrido[1,2-a]pyrimidin-4-one (PP) derivatives through the Rv3087 protein.

N-Heterocyclic Carbene-Promoted [4+2] Annulation of α-Chloro Hydrazones with α-Chloro Aliphatic Aldehydes to Access Enantioenriched Dihydropyridazinones

An expeditious protocol for the assembly of chiral 4,5-dihydropyridazin-3(2H)-ones from α-chloro hydrazones and α-chloro aliphatic aldehydes via N-heterocyclic carbene (NHC) catalysis is outlined. These in situ-generated 1,2-diaza-1,3-dienes undergo asymmetric [4+2] annulation with NHC-bound enolates to afford the desired products bearing a stereogenic center at the C4 position. The notable features of this approach include good to excellent enantioselectivities, high functional group tolerance, mild reaction conditions, simple operating procedures, and compatibility with gram-scale synthesis.

Carbene-catalyzed enantioselective annulation of dinucleophilic hydrazones and bromoenals for access to aryl-dihydropyridazinones and related drugs

4,5-Dihydropyridazinones bearing an aryl substituent at the C6-position are important motifs in drug molecules. Herein, we developed an efficient protocol to access aryl-dihydropyridazinone molecules via carbene-catalyzed asymmetric annulation between dinucleophilic arylidene hydrazones and bromoenals. Key steps in this reaction include polarity-inversion of aryl aldehyde-derived hydrazones followed by chemo-selective reaction with enal-derived α,β-unsaturated acyl azolium intermediates. The aryl-dihydropyridazinone products accessed by our protocol can be readily transformed into drugs and bioactive molecules.

Polarity inversion of arylidene hydrazones to react with bromoenals via carbene organic catalysis is disclosed. The reaction enantioselectively affords 6-aryl-4,5-dihydropyridazinones and related drugs with proven commercial applications.

Synthesis, in-vitro evaluation, molecular docking, and kinetic studies of pyridazine-triazole hybrid system as novel α-glucosidase inhibitors

In this study, we reported the discovery of pyridazine based 1,2,3-triazole derivatives as inhibitors of α-glucosidase. All target compounds exhibited significant inhibitory activities against yeast and rat α-glucosidase enzymes compared to positive control, acarbose. The most potent compound 6j, ethyl 3-(2-(1-(4-nitrobenzyl)-1H-1,2,3-triazol-4-yl)ethyl)-5,6-diphenylpyridazine-4-carboxylate exhibited IC₅₀ values of 58, and 73 µM. Docking studies indicated the responsibility of hydrophobic and hydrogen bonding interactions in the ligand-enzyme complex stability. The in-vitro safety against the normal cell line was observed by toxicity evaluation of the selected compounds.

Azolo[d]pyridazinones in medicinal chemistry

Azolo[d]pyridazinone is a privileged structure and versatile pharmacophore whose derivatives are associated with diverse biological activities, in particular antidiabetic, antiasthmatic, anticancer, analgesic, anti-inflammatory, antithrombotic, antidepressant and antimicrobial activities. The importance of this scaffold against some targets like PDE, COX and DPP-4 has been reviewed in detail previously. In the present review, we have summarized comprehensive information on azolo[d]pyridazinone derivatives investigated by many researchers for their diverse pharmacological activities, structure-activity relationship and molecular modeling studies since 2000. The review may lead scientists in the research fields of organic synthesis, medicinal chemistry and pharmacology to the strategic design and development of azolo[d]pyridazinone-based drug candidates in the future.

[4 + 2] Annulation Reaction of In Situ Generated Azoalkenes with Azlactones: Access to 4,5-Dihydropyridazin-3(2H)-Ones

An unprecedented [4 + 2] annulation reaction between in situ formed azoalkenes and azlactones has been developed. This reaction provides a facile access to an array of 4,5-dihydropyridazin-3(2H)-one derivatives, which are very promising in medicinal applications as potential biologically active candidates. Notably, these dihydropyridazinones could also be synthesized via a one-pot reaction protocol by using the in situ formed azlactones from N-acyl amino acids and in situ generated azoalkenes from α-halogeno hydrazones. The potential applications of the methodology were also demonstrated by gram-scale experiments and the versatile conversions of the products into other nitrogen-containing compounds.

Experimental and Computational Approaches for Solubility Measurement of Pyridazinone Derivative in Binary (DMSO + Water) Systems

The current research work was performed to evaluate the solubilization behavior, solution thermodynamics, and solvation behavior of poorly soluble pyridazinone derivative i.e., 6-phenyl-pyridazin-3(2H)-one (PPD) in various binary solvent systems of dimethyl sulfoxide (DMSO) and water using experimental and various computational approaches. The solubility of PPD in various binary solvent system of DMSO and water was investigated within the temperature range T = 298.2 K to 318.2 K at constant air pressure p = 0.1 MPa, by employing an isothermal technique. The generated solubility data of PPD was computationally represented by five different cosolvency models including van't Hoff, Apelblat, Yalkowsky-Roseman, Jouyban-Acree, and Jouyban-Acree-van't Hoff models. The performance of each computational model for correlation studies was illustrated using root mean square deviations (RMSD). The overall RMSD value was obtained <2.0% for each computational model. The maximum solubility of PPD in mole fraction was recorded in neat DMSO (4.67 × 10-1 at T = 318.2 K), whereas the lowest one was obtained in neat water (5.82 × 10-6 at T = 298.2 K). The experimental solubility of PPD in mole fraction in neat DMSO was much higher than its ideal solubility, indicating the potential of DMSO for solubility enhancement of PPD. The computed values of activity coefficients showed maximum molecular interaction in PPD-DMSO compared with PPD-water. Thermodynamic evaluation showed an endothermic and entropy-driven dissolution of PPD in all the mixtures of DMSO and water. Additionally, enthalpy-entropy compensation evaluation indicated an enthalpy-driven mechanism as a driven mechanism for the solvation property of PPD.

Synthesis, Characterization and Solubility Determination of 6-Phenyl-pyridazin-3(2H)-one in Different Pharmaceutical Solvents

The current research work proposed the solubility data and solution thermodynamic properties of the cardiovascular agent 6-phenylpyridazin-3(2H)-one [PPD] in twelve pharmaceutical solvents at "T = 298.2 K to 318.2 K" and "p = 0.1 MPa". The measured solubilities of PPD were regressed well with "van't Hoff and Apelblat models". The solid phases of pure and equilibrated PPD were characterized using differential scanning calorimetry and powder X-ray differactometry, and the results suggested no transformation of PPD into solvates/hydrates/polymorphs after equilibrium. The solubilities of PPD in a mole fraction at "T = 318.2 K" were noted at a maximum in dimethyl sulfoxide (DMSO, 4.73 × 10^-1), followed by polyethylene glycol-400 (PEG-400, 4.12 × 10^-1), Transcutol^® (3.46 × 10^-1), ethyl acetate (EA, 81 × 10^-2), 2-butanol (2.18 × 10^-2), 1-butanol (2.11 × 10^-2), propylene glycol (PG, 1.50 × 10^-2), isopropyl alcohol (IPA, 1.44 × 10^-2), ethylene glycol (EG, 1.27 × 10^-2), ethanol (8.22 × 10^-3), methanol (5.18 × 10^-3) and water (1.26 × 10^-5). Similar tendencies were also noted at other studied temperatures. The results of the "apparent thermodynamic analysis" showed an endothermic and entropy-driven dissolution of PPD in all pharmaceutical solvents. The results of the activity coefficients suggested a maximum interaction at the molecular level in PPD-DMSO, PPD-PEG-400 and PPD-Transcutol, compared with other combination of the solute and solvents.

Novel compounds of hybrid structure pyridazinone–coumarin as potent inhibitors of platelet aggregation

Aim: The current limitations of antiplatelet therapy promote the search for new antithrombotic agents. Here we describe novel platelet aggregation inhibitors that combine pyridazinone and coumarin scaffolds in their structure. Results: The target compounds were synthesized in good yield from maleic anhydride, following a multistep strategy. The in vitro studies demonstrated significant antiplatelet activity in many of these compounds, with IC50 values in the low micromolar range, revealing that the activity was affected by the substitution pattern of the two selected cores. Additional studies point out their effect as inhibitors of glycoprotein (Gp) IIb/IIIa activation. Conclusion: This novel hybrid structure can be considered a good prototype for the development of potent platelet aggregation inhibitors.

In Vitro Antimicrobial Activities of 6-Substituted-3(2H)- pyridazinone-2-acetyl-2- (substituted/nonsubstitutedbenzal/ acetophenone) Hydrazone Derivatives

Aim: In vitro antibacterial activity of 6-substituted-3(2H)-pyridazinone-2-acetyl-2-(substituted/nonsubstitutedbenzal/ acetophenone) hydrazone derivatives were tested in common species causing hospital-acquired infections. Material and Method: Antimicrobial activities of the compounds were performed by determining minimum inhibitory concentration (MIC) value against four Gram-positive, five Gram-negative and four Candida species fungi. Modified serial microdilution method was carried out. Reference strains of American Type Culture Collection (ATCC) were used. Results: In general, eleven compounds exhibited considerable activity. Comparatively, compound 3 exhibited strong activity against Enterobacter hormaechei and 5, 11 were the most active against Acinetobacter baumannii at 31.25 μg/mL. Compounds 1,2,3,4,8 and 10 were found to be as active as positive control ampicillin trihidrate against Stenotrophomonas maltophilia. On the other hand, compounds 1,2,3,4,7,8,9,10 and 11 showed strong antifungal activitiy as much as fluconazole against Candida tropicalis. Compound 1 was mostly active against Candida albicans, Candida glabrata, Candida parapsilosis and Candida tropicalis. It was also revealed that the antifungal activity of compounds 1, 6, 7, 8 and 9 were higher than the others. Compound 1 and 8 exhibited the best activity against Candida glabrata and Candida parapsilosis respectively. Conclusions: All tested compounds showed better activity against Gram-negative bacteria and yeast than Gram-positive bacteria. These compounds may be considered as alternative antimicrobial agents in the treatment of multiple drug resistant Gram-negative, Gram-positive bacteria and fungal pathogens. Especially, we suggested that Compound 1 and 8 might be a promising candidate of new antifungal agents

Solubility and Thermodynamics of 6-Phenyl-4,5-dihydropyridazin-3(2H)-one in Various (PEG 400+Water) Mixtures

The aim of this study was to determine the solubility of pyridazinone derivative 6-phenyl-4,5-dihydropyridazin-3(2H)-one (PDP-6) in different “polyethylene glycol 400 (PEG 400)+water” mixtures at temperatures “T=293.2 K to 313.2 K” and pressure “p=0.1 MPa”. The solubilities of PDP-6 were determined using an isothermal method and correlated with Apelblat, van’t Hoff and Yalkowsky–Roseman models. The maximum solubilities of PDP-6 in mole fraction were obtained in neat PEG 400 (8.46×10−2 at T=313.2 K). However, the minimum one was recorded in neat water (7.50×10−7 at T=293.2 K). Apparent thermodynamic analysis showed an endothermic dissolution of PDP-6 in all (PEG 400 water) mixtures. Based on the solubility data of the current study, PDP-6 has been considered as practically insoluble in water and soluble in PEG 400.

Efficient 1,3,4-Thiadiazole-4,5-dihydropyridazin-3(2H)-ones as Antimicrobial Agents

A set of novel series of 1,3,4-thiadiazolyl-sulfanyl-4,5-dihydropyridazin-3(2H)-ones with anticipated antimicrobial activity has been synthesized. The synthetic protocol of the targeted compounds was accomplished by treating β-aroylacrylic acid 1 with 5-amino-1,3,4-thiadiazole-2-thiol (2) to afford the thia-Michael adduct 3. Afterwards, the obtained thia-Michael adduct 3 was cyclized to 4,5-dihydropyridazin-3(2H)-ones 4a-d and the non-cyclized product hydrazone 5 by using different hydrazines. Moreover, adduct 3 was reacted with esters like diethyl malonate and ethyl acetoacetate affording 1,3,4-thiadiazolobutanamides 6a, b. Furthermore, the concurrent reaction of later butamides 6a, b with the hydrazine derivatives furnished thiadiazolopyridazin-3(2H)-ones 7a-d, 8, and butanoic acid 9.

Development of novel pyridazinone-based adenosine receptor ligands

With the aim of finding new adenosine receptor (AR) ligands, a preliminary investigation focusing on the thieno[2,3-d]pyridazin-5(4H)-one scaffold was undertaken. The synthesized compounds 1-11 were evaluated for their binding at hA₁, hA_2A and hA₃ ARs and efficacy at hA_2B subtype in order to determine the affinity at the human adenosine receptor subtypes. Small structural changes on this scaffold highly influenced affinity; compound 5 (5-ethyl-7-(thiazol-2-yl)thieno[2,3-d]pyridazin-4(5H)-one) emerged as the best of this series. The simplicity of the synthetic process, the capability of the scaffold to be easily decorated, together with the predicted ADME properties confirm the role of these compounds as promising hits. A molecular docking investigation at the hA₁AR crystal structure was performed to rationalize the SARs of the herein reported thienopyridazinones.

Recent Progress in the Chemistry of Pyridazinones for Functional Group Transformations

While N-hetereocycles have received significant attention in organic synthesis and other research fields, the chemistry of pyridazine, a six-membered aromatic ring with two adjacent nitrogen atoms, and its derivatives has been relatively little understood. This Synopsis describes recent progress made in the synthesis of pyridazine derivatives-particularly, pyridazin-3(2H)-ones-and their utility as efficient and recyclable functional group carriers for various important organic reactions.

Synthesis, molecular docking and biological evaluation of some newer 2-substituted-4-(benzo[d][1,3]dioxol-5-yl)-6-phenylpyridazin-3(2H)-ones as potential anti-inflammatory and analgesic agents

A new series of 2-substituted-4-(benzo[d][1,3]dioxol-5-yl)-6-phenylpyridazin-3(2H)-one derivatives has been synthesized and studied. The in vivo anti-inflammatory and analgesic activities of the synthesized compounds were evaluated using carrageen rat paw edema model and acetic acid induced writhing model, respectively. Side effect profile of the newly synthesized pyridazinones was assessed by gastric ulcerogenic and anti-platelet activity. The compounds were further evaluated for their inhibitory activity against cyclooxygenase enzyme (COX-1/COX-2) by in vitro colorimetric COX (ovine) inhibitor screening assay method. The p-flourophenylpiperazine substituted analogue 14 exhibited most potent anti-inflammatory and analgesic activities with lower ulcer index and extremely good selectivity towards COX-2 versus COX-1 enzyme with a selectivity index of 10. Molecular docking studies showed appreciable binding of new pyridazinone analogues with the amino acids present at the active site of hCOX-2 enzyme.

Pyridazinone: an attractive lead for anti-inflammatory and analgesic drug discovery

In spite of the availability of a large number of anti-inflammatory and analgesic agents, fighting pain and inflammation remains a common problem. The current review article discusses the need of novel therapeutic targets for risk-free anti-inflammatory and analgesic therapy and summarizes some new agents in various stages of drug discovery pipeline. Pyridazin-3(2H)-ones are nitrogen-rich heterocyclic compounds of considerable medicinal interest due to their diverse biological activities. The current review article focuses on progressive development of this attractive scaffold for the design and synthesis of new pyridazinone-based anti-inflammatory and analgesic agents. Mechanistic insights into the anti-inflammatory and analgesic properties of pyridazinone derivatives and various synthetic techniques used for their synthesis are also described.

N-Heterocyclic carbene-catalyzed [3 + 3] cyclocondensation of bromoenals with hydrazones: highly enantioselective synthesis of dihydropyridazones

The N-heterocyclic carbene-catalyzed [3 + 3] cyclocondensation of bromoenals and hydrazones is developed to give the corresponding chiral 4,5-dihydropyridazones in good yields with excellent enantioselectivities.

N-Heterocyclic Carbene-Catalyzed Oxidative Annulations of α,β-Unsaturated Aldehydes with Hydrazones: Selective Synthesis of Optically Active 4,5-Dihydropyridazin-3-ones and Pyridazin-3-ones

A novel and efficient method for the highly enantioselective synthesis of chiral 4,5-dihydropyridazin-3-one derivatives has been developed based on the chiral N-heterocyclic carbene-catalyzed oxidative annulation between α,β-unsaturated aldehydes and hydrazones. Meanwhile, the selective synthesis of either 4,5-dihydropyridazin-3-ones or pyridazin-3-one derivatives from the same reactants has been achieved by simply varying catalytic and reaction conditions.

Solid-state Reaction of Azolium Hydrohalogen Salts with Silver Dicyanamide--Unexpected Formation of Cyanoguanidine-azoles, Reaction Mechanism and Their Hypergolic Properties

Cyanoguanidines as well as azoles are important bioactive groups, which play an important role in the medical application; meanwhile, the high nitrogen content makes them excellent backbones for energetic materials. A Novel and simple method that combined these two fragments into one molecular compound was developed through the transformation of dicyanamide ionic salts. In return, compounds 4–11 were synthesized, and fully characterized by IR, MS, NMR and elemental analysis. Meanwhile, the structures of compounds 4, 8 and 11 were confirmed by X-ray crystal diffraction. Detailed reaction mechanisms were studied through accurate calculations on the reaction energy profiles of the azolium cations and DCA anion, which revealed the essence of the transformation proceeding. Meanwhile, compound 8 exhibits excellent hypergolic property, which could be potentially novel molecular hypergolic fuel.

Tautomerism in pyridazin-3(2H)-one: a theoretical study using implicit/explicit solvation models

The tautomeric conversion of pyridazin-3(2H)-one 1 into pyridazin-3-ol 2 has been theoretically studied using density functional theory (DFT) methods at the B3LYP/6-311++G** level. Two mechanisms have been considered for this process: (i) one in which the hydrogen is directly transferred through TS12; and (ii) another one in which a double hydrogen transfer takes place via TS1122 upon formation of the corresponding dimer. The former requires a very high activation energy of 42.64kcal/mol as a consequence of the strain associated with the formation of the four-membered TS12, while the latter requires a much lower activation energy, 14.66kcal/mol. Implicit, explicit, and a combination of both implicit and explicit solvation models, using both protic and aprotic polar solvents, have been considered for the first mechanism. This study allows the establishment of the requirement to use protic polar solvents in order to reduce the high activation energy associated with TS12.