The therapeutic journey of pyridazinone

Design and Synthesis of Edaravone Derivatives Containing 6-(4-aminophenyl)-4,5-dihydropyridazin-3(2H)-one as Bifunctional Anti-ischemic Stroke Agents

Ischemic stroke gravely endangers human health. To develop novel drugs with antiplatelet and neuroprotective functions for ischemic stroke, edaravone derivatives CT01-CT20, containing 6-(4-aminophenyl)-4,5-dihydropyridazin-3(2H)-one, were synthesized from materials like dimethyl butynedioate, ethyl acetoacetate, and diethyl 1,3-acetonedicarboxylate, via cyclization, hydrolysis, and condensation. Among them, CT16 exhibited outstanding antiplatelet activity (IC50 = 6.72 µM), absent in edaravone. It also surpassed edaravone in 1,1-diphenyl-2-picrylhydrazyl radical scavenging (EC50 = 30.80 µM) and protecting PC12 cells from H₂O₂ damage. In vivo, CT16 effectively reduced carotid artery thrombosis in rats and enhanced blood flow. In the middle cerebral artery occlusion reperfusion injury model, it shrank infarct size, improved neurological scores, increased cerebral blood flow, and lessened brain edema. Preliminary safety tests indicated CT16 didn't alter rat blood biochemistry or organ pathology, with a low bleeding risk as an antiplatelet agent. Molecular docking suggested it may inhibit phosphodiesterase 3A to achieve an antiplatelet effect. In conclusion, CT16 has both antiplatelet aggregation and neuroprotective effects and is a potential candidate compound for the treatment of ischemic stroke.

Therapeutic Potential of Tricyclic Pyridazinone-Based Molecules: An Overview

Pyridazin-3(2H)one-based molecules have always attracted the attention of medicinal chemists due to their different pharmacological properties. The incorporation of such nuclei in therapeutically active molecules either as monocyclic units or as fused bi- or tricyclic scaffolds results in a wide range of pharmacological effects such as anti-inflammatory, analgesic, anticancer, antimicrobial, antiviral, cardiovascular-protective, antiulcer, and many other useful pharmacological activities. In accordance with our consolidated experience gained over the years in the chemistry and biology of tricyclic pyridazin-3(2H)ones, this review summarizes SAR studies of such pyridazinone-based polycyclic compounds endowed with various biological and therapeutic properties.

7-(4-Chlorophenyl)-1-hydroxy-5-methylpyrido[3,4-d]pyridazin-4(3H)-one: synthesis, solvatomorphism, in vitro anti-inflammatory and cytotoxic activity studies and in silico analysis

The newly obtained compound 7-(4-chlorophenyl)-1-hydroxy-5-methylpyrido[3,4-d]pyridazin-4(3H)-one (CPM) was crystallized as two new variable solvates, namely, the dimethyl sulfoxide monosolvate, C14H10ClN3O2·C2H6SO (I), and the sesquisolvate, C14H10ClN3O2·1.5C2H6SO (II), and their structures were confirmed by single-crystal X-ray diffraction analysis. In previous work, 1-hydroxy-5-methyl-7-phenylpyrido[3,4-d]pyridazin-4(3H)-one (PM) was found to display anticancer activity. In the next step of our studies, we synthesized a new derivative of PM, introducing a Cl atom into the PM structure, obtaining CPM, which showed not only anticancer but also anti-inflammatory activity. CPM and the new semi-products of each step of the synthesis were examined by 1H NMR, 13C NMR and FT-IR spectroscopic analyses, and mass spectrometry. CPM forms (I) and (II) crystallize in the triclinic P1 and monoclinic C2/c space groups, respectively, and differ in the stoichiometry of the CPM and DMSO molecules in the crystal lattice, being 1:1 and 1:1.5 for (I) and (II), respectively. A powder X-ray diffraction analysis was performed only for solvate (I) due to the lack of stability of solvate (II). The potential cytotoxicity of CPM was evaluated against the normal cell lines L929 and RPTEC, as well as the cancer cell lines A172, AGS, CACO-2 and HepG2. The anti-inflammatory activity of CPM was also evaluated using colorimetric assay for the inhibition of COX-1 and COX-2. The same biological tests were carried out for PM to compare the activities of both compounds. The biological studies revealed that CPM does not exhibit more activity than PM. Moreover, in silico analysis of the bioavailability and molecular docking were performed.

Development of 1,2,3-Triazolopyridazinone Derivatives as Potential Caspase 3 and Apoptosis Inducers: Design, Synthesis and Anticancer Activity Studies

Herein, the synthesis, anticancer activity and apoptotic pathways of 1,2,3-triazolopyridazinones compounds, which are similar to DNA bases not previously found in the literature have been investigated. To achieve this goal, it is designed the hybrid molecules combining triazole and pyridazinone/pyridazithione structures, bearing a lipophilic group (benzyl/phenyl) at the one position and benzene with electron withdrawing or donating groups at five positions, with high pharmacophoric properties on the same scaffold structure. The representative compounds in this series 5a, 5c, 6a and 8c exhibited higher anticancer activity than other compounds and cisplatin control against breast (MCF-7) and lung (A549) cell lines. These compounds were less toxic when tested against the noncancerous L929 cell line. In addition, the apoptotic effect mechanisms of these compounds were confirmed by AO/EB staining and caspase 3 activity results. These findings indicate that some derivatives of these compounds could be effective therapeutic agents for the treatment of cancer disease with an apoptosis-promoting.

Synthesis, Characterization, and Molecular Modeling Studies of Novel Indenopyridazine-thiazole Molecular Hybrids

Background:

Previous studies have reported various biological activities of indeno-pyridazine and thiazole derivatives, including antiviral activity and CoV-19 inhibition. In this paper, the authors aimed to design, synthesize, and characterize a novel series of indenopyridazinethiazoles, starting with 2-(4-cyano-3-oxo-2,3-dihydro-9H-indeno[2,1-c]pyridazin-9-ylidene)-hydrazine-1-car-bothioamide and available laboratory reagents.

Methods:

The strategy involved the synthesis of indeno[2,1-c]pyridazincarbothioamide, followed by its reaction with various hydrazonoyl chlorides and α-halocompounds (phenacyl bromides and α-chloroketones) to obtain the desired indenopyridazinethiazole derivatives. The synthesized structures were confirmed using IR, NMR, mass spectra, elemental analysis, and alternative synthesis when possible. Docking scores and poses of thirteen synthesized compounds were examined using Auto-Dock4.2.6 software against multiple targets of SARS-CoV-2, including 3C-like protease (3CLpro), helicase, receptor binding domain (RBD), papain-like protease (PLpro), neuropilin-1 (NRP-1), RNA-dependent RNA polymerase (RdRp), and human angiotensin‐converting enzyme 2 (ACE2).

Results:

Docking predictions revealed that compound 13d exhibited high potency against 3CLpro and helicase, with docking scores of -10.9 and -10.5 kcal/mol, respectively. Compound 10c showed su-perior docking scores against RBD and ACE2, with values of -8.7 and -11.8 kcal/mol, respectively. Compounds 10a, 13c, and 7b demonstrated excellent docking scores against RdRp, PLpro, and NRP-1, with values of -10.3, -10.4, and -8.6 kcal/mol, respectively.

Conclusion:

The authors recommend further experimental assessments of compounds 13d, 10c, 10a, 13c, and 7b against SARS-CoV-2 multi-targets, considering their promising docking scores.

Pyridazine and pyridazinone compounds in crops protection: a review

Pyridazine and pyridazinone belong to the same group of six-membered heterocyclic compounds, and both structurally feature two adjacent nitrogen atoms. Pyridazine and pyridazinone derivatives are frequently used as core structures in the development of new green agrochemicals due to their high activity and environmental friendliness, attracting significant attention from researchers in recent years. Over the past 20 years, significant developments have occurred in the field of pyridazine and pyridazinone derivatives, which exhibit insecticidal, fungicidal, herbicidal, antiviral, and plant growth regulating activities. Hence, summarizing the process of creating novel molecules with pyridazine and pyridazinone structures through design concepts, understanding structure-activity relationships, and mechanisms of action is an important undertaking. This review aims to provide a comprehensive overview of these advancements, shedding light on the discovery and mechanism of action of novel pesticides in the pyridazine and pyridazinone categories.

Novel pyridazinone derivatives bind to KSRP: Synthesis, anti-tumor biological evaluations and modelling insights

Pyridazinone derivatives have been extensively used as anticancer agents. IMB5036 is a structure specific pyridazinone compound with potential antitumor activity via targeting KSRP protein which controls gene expression at multiple levels. In this study, fifteen IMB5036 analogues were synthesized and preliminary structure-activity relationships were explored. Among them, compounds 8 and 10 exhibited remarkably anti-proliferation of various cancer cells and a good cancer cell selectivity (against human fetal hepatocyte L02 cells). More detailed investigation was included that both 8 and 10 inhibited colony formation and migration in concentration-dependent mode against MCF-7 cells. Additionally, 8 and 10 induced apoptosis and cell cycle arrest, decreased mitochondrial membrane potential, damaged DNA, and increased reactive oxygen species. Moreover, 8 displayed a potent antitumor efficacy (TGI = 74.2 %, at a dose of 30 mg/kg) in MCF-7 xenograft model by i.p. injection. Further, we synthesized a biotinylated probe 16 for identifying the detail domain of KSRP. Through pull down assay and molecular docking study, we validated that the KH23 domain functioned as the binding pocket for the compounds. Thus, compound 8 was identified as a novel targeting KSRP pyridazinone-based compound and exhibited excellent antitumor activity both in vitro and in vivo.

Novel Dual Acetyl- and Butyrylcholinesterase Inhibitors Based on the Pyridyl-Pyridazine Moiety for the Potential Treatment of Alzheimer's Disease

Background: Alzheimer's disease (AD) is characterized by cholinergic dysfunction, making the inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) critical for improving cholinergic neurotransmission. However, the development of effective dual inhibitors remains challenging. Objective: This study aims to synthesize and evaluate novel pyridazine-containing compounds as potential dual inhibitors of AChE and BuChE for AD treatment. Methods: Ten novel pyridazine-containing compounds were synthesized and characterized using IR, 1H NMR, and 13C NMR. The inhibitory activities against AChE and BuChE were assessed in vitro, and pharmacokinetic properties were explored through in silico ADME studies. Molecular dynamics simulations were performed for the most active compound. Results: Compound 5 was the most potent inhibitor, with IC50 values of 0.26 µM for AChE and 0.19 µM for BuChE, outperforming rivastigmine and tacrine, and showing competitive results with donepezil. Docking studies revealed a binding affinity of -10.21 kcal/mol to AChE and -13.84 kcal/mol to BuChE, with stable interactions confirmed by molecular dynamics simulations. In silico ADME studies identified favorable pharmacokinetic properties for compounds 5, 8, and 9, with Compound 5 showing the best activity. Conclusions: Compound 5 demonstrates strong potential as a dual cholinesterase inhibitor for Alzheimer's disease, supported by both in vitro and in silico analyses. These findings provide a basis for further optimization and development of these novel inhibitors.

Innovations in Nuclear Medicine Imaging for Reactive Oxygen Species: Applications and Radiopharmaceuticals

Reactive oxygen species (ROS) are generated during normal cellular energy production and play a critical role in maintaining cellular function. However, excessive ROS can damage cells and tissues, contributing to the development of diseases such as cardiovascular, inflammatory, and neurodegenerative disorders. This review explores the potential of nuclear medicine imaging techniques for detecting ROS and evaluates various radiopharmaceuticals used in these applications. Radiopharmaceuticals, which are drugs labeled with radionuclides, can bind to specific biomarkers, facilitating their identification in vivo using nuclear medicine equipment, i.e., positron emission tomography and single photon emission computed tomography, for diagnostic purposes. This review includes a comprehensive search of PubMed, covering radiopharmaceuticals such as analogs of fluorescent probes and antioxidant vitamin C, and biomarkers targeting mitochondrial complex I or cystine/glutamate transporter.

Synthesis, crystal structure and Hirshfeld surface analysis of 2-{4-[(2-chloro-phen-yl)meth-yl]-3-methyl-6-oxopyridazin-1-yl}-N-phenyl-acetamide

In the title mol-ecule, C20H18ClN3O2, the 2-chloro-phenyl group is disordered to a small extent [occupancies 0.875 (2)/0.125 (2)]. The phenyl-acetamide moiety is nearly planar due to a weak, intra-molecular C-H⋯O hydrogen bond. In the crystal, N-H⋯O hydrogen bonds and π-stacking inter-actions between pyridazine and phenyl rings form helical chains of mol-ecules in the b-axis direction, which are linked by C-H⋯O hydrogen bonds and C-H⋯π(ring) inter-actions. A Hirshfeld surface analysis was performed, which showed that H⋯H, C⋯H/H⋯C and O⋯H/H⋯O inter-actions to dominate the inter-molecular contacts in the crystal.

Bacterial Hydrazine Biosynthetic Pathways Featuring Cupin/Methionyl tRNA Synthetase-like Enzymes

Nitrogen-Nitrogen (N-N) bond-containing functional groups in natural products and synthetic drugs play significant roles in exerting biological activities. The mechanisms of N-N bond formation in natural organic molecules have garnered increasing attention over the decades. Recent advances have illuminated various enzymatic and nonenzymatic strategies, and our understanding of natural N-N bond construction is rapidly expanding. A group of didomain proteins with zinc-binding cupin/methionyl-tRNA synthetase (MetRS)-like domains, also known as hydrazine synthetases, generates amino acid-based hydrazines, which serve as key biosynthetic precursors of diverse N-N bond-containing functionalities such as hydrazone, diazo, triazene, pyrazole, and pyridazinone groups. In this review, we summarize the current knowledge on hydrazine synthetase mechanisms and the various pathways employing this unique bond-forming machinery.

Discovery of Novel Hybrids of Edaravone and 6-Phenyl-4,5-dihydropyridazin-3(2H)-one with Antiplatelet Aggregation and Neuroprotection for Ischemic Stroke Treatment

Drugs with anti-platelet aggregation and neuroprotection are of great significance for the treatment of ischemic stroke. A series of edaravone and 6-phenyl-4,5-dihydropyridazin-3(2H)-one hybrids were designed and synthesized. Among them, 6g showed the most effective cytoprotective effect against oxygen-glucose deprivation/reoxygenation-induced damage in BV2 cells and an excellent inhibitory effect on platelet aggregation induced by adenosine diphosphate and arachidonic acid. Additionally, 6g could prevent thrombosis caused by ferric chloride in rats and pose a lower risk of causing bleeding compared with aspirin. It provides better protection against ischemia/reperfusion injury in rats compared with edaravone and alleviates the oxidative stress related to cerebral ischemia/reperfusion by increasing the GSH and SOD levels and decreasing the MDA concentration. Finally, molecular docking results showed that 6g probably acts on PDE3 A and plays an anti-platelet aggregation effect. Overall, 6g could be a potential candidate compound for the treatment of ischemic stroke.

Dinuclear Zn-Catalytic System as Brønsted Base and Lewis Acid for Enantioselectivity in Same Chiral Environment

Zinc (Zn) is a crucial element with remarkable significance in organic transformations. The profusion of harmless zinc salts in the Earth's outer layer qualifies zinc as a noteworthy contender for inexpensive and eco-friendly reagents and catalysts. Recently, widely recognized uses of organo-Zn compounds in the field of organic synthesis have undergone extensive expansion toward asymmetric transformations. The ProPhenol ligand, a member of the chiral nitrogenous-crown family, exhibits the spontaneous formation of a dual-metal complex when reacted with alkyl metal (R-M) reagents, e.g., ZnEt2. The afforded Zn complex possesses two active sites, one Lewis acid and the other Brønsted base, thereby facilitating the activation of nucleophiles and electrophiles simultaneously within the same chiral pocket. In this comprehensive analysis, we provide a thorough account of the advancement and synthetic potential of these diverse catalysts in organic synthesis, while emphasizing the reactivity and selectivities, i.e., dr and ee due to the design/structure of the ligands employed.

Anti-Inflammatory and Antioxidant Pyrrolo[3,4-d]pyridazinone Derivatives Interact with DNA and Bind to Plasma Proteins-Spectroscopic and In Silico Studies

From the point of view of the search for new pharmaceuticals, pyridazinone derivatives are a very promising group of compounds. In our previous works, we have proved that newly synthesized ligands from this group have desirable biological and pharmacokinetic properties. Therefore, we decided to continue the research evaluating the activity of pyrrolo[3,4-dpyridazinone derivatives. In this work, we focused on the interactions of five pyridazinone derivatives with the following biomolecules: DNA and two plasma proteins: orosomucoid and gamma globulin. Using several of spectroscopic methods, such as UV-Vis, CD, and fluorescence spectroscopy, we proved that the tested compounds form stable complexes with all biomacromolecules selected for analysis. These findings were also confirmed by the results obtained by molecular modeling. All tested pyridazinone derivatives bind to the ctDNA molecule via groove binding mechanisms. All these molecules can also be bound and transported by the tested plasma proteins; however, the stability of the complexes formed is lower than those formed with serum albumin.

One-Pot Synthesis of Polycyclic 4,5-Dihydropyridazine-3(2H)-ones by Inverse Electron-Demand Diels-Alder (IEDDA) Reactions from Alkenes

In the classical Inverse Electron-Demand Diels-Alder (IEDDA) reactions between alkenes and tetrazines, 4,5-dihydropyridazines are formed. 4,5-Dihydropyridazines are rapidly converted to the more energetically stable 1,4-dihydropyridazines by 1,3-prototropic isomerization. In this study, instead of 1,4-dihydropyridazines, 4,5-dihydropyridazine-3(2H)-ones were obtained as a result of IEDDA reactions between tetrazines with leaving groups at the 3,6-positions, and norbornene and barrelene-derived polycyclic alkenes in the presence of moisture in air or solvent. To show that this new method works not only on strained polycyclic alkenes but also on monocyclic and linear alkenes, the corresponding 4,5-dihydropyridazine-3(2H)-ones were obtained in high yields from the reactions performed with styrene and cyclopentene as well. The chemical structures of the polycyclic 4,5-dihydropyridazine-3(2H)-ones were determined by NMR and HRMS analyses. In addition, the exact structures of the polycyclic 4,5-dihydropyridazine-3(2H)-ones were also experimentally proven by converting them to pyridazine-3(2H)-ones known in the literature.

A visible light-driven direct synthesis of industrially relevant glutaric acid diesters from aldehydes

A straightforward and practical method has been developed to access α-substituted glutaric diesters from acrylates and aldehydes using visible light, with Eosin Y facilitating hydrogen atom transfer (HAT) and subsequent Giese-type addition. Also, sunlight has been successfully used as an alternative sustainable light source. The method has also been explored to access substituted 4,5-dihydro-2H-pyridazinones, which have potential biological and industrial applications. Comprehensive mechanistic investigations have been carried out.

Exploring Three Avenues: Chemo- and Regioselective Transformations of 1,2,4-Triketone Analogs into Pyrazoles and Pyridazinones

A convenient approach to substituted pyrazoles and pyridazinones based on 1,2,4-triketones is presented. Chemo- and regiocontrol in condensations of t-Bu, Ph-, 2-thienyl-, and CO2Et-substituted 1,2,4-triketone analogs with hydrazines are described. The direction of preferential nucleophilic attack was shown to be switched depending on the substituent nature in triketone as well as the reaction conditions. The acid and temperature effects on the selectivity of condensations were revealed. Regiochemistry of heterocyclic core formation was confirmed by NMR and XRD studies. The facile construction of heterocyclic motifs bearing acetyl and (or) carbethoxy groups suggests them as promising mono- or bifunctional building blocks for subsequent transformations.

Oxygen-Promoted 6-endo-trig Cyclization of β,γ-Unsaturated Hydrazones/Ketoximes with Diazonium Tetrafluoroborates for Pyridazin-4(1H)-ones/Oxazin-4(1H)-ones

An oxidative 6-endo-trig cyclization and [2 + 2] cycloaddition of β,γ-unsaturated hydrazones/ketoximes and diazonium tetrafluoroborates for a synthetic strategy to pyridazin-4(1H)-ones/oxazin-4(1H)-ones under metal-free conditions is presented in a one-pot procedure. This protocol features excellent functional group tolerance and remarkable regioselectivity. A mechanistic study has been verified via 18O labeling and the H218O labeling method, in which O2 acts as both a reaction component and an oxidant.

Privileged Scaffolds for Potent and Specific Inhibitors of Mono-ADP-Ribosylating PARPs

The identification of new targets to address unmet medical needs, better in a personalized way, is an urgent necessity. The introduction of PARP1 inhibitors into therapy, almost ten years ago, has represented a step forward this need being an innovate cancer treatment through a precision medicine approach. The PARP family consists of 17 members of which PARP1 that works by poly-ADP ribosylating the substrate is the sole enzyme so far exploited as therapeutic target. Most of the other members are mono-ADP-ribosylating (mono-ARTs) enzymes, and recent studies have deciphered their pathophysiological roles which appear to be very extensive with various potential therapeutic applications. In parallel, a handful of mono-ARTs inhibitors emerged that have been collected in a perspective on 2022. After that, additional very interesting compounds were identified highlighting the hot-topic nature of this research field and prompting an update. From the present review, where we have reported only mono-ARTs inhibitors endowed with the appropriate profile of pharmacological tools or drug candidate, four privileged scaffolds clearly stood out that constitute the basis for further drug discovery campaigns.

Synthesis, crystal structure, DFT, Hirshfeld surface analysis, energy framework, docking and molecular dynamic simulations of (E)-4-(4-methylbenzyl)-6-styrylpyridazin-3(2H)-one as anticancer agent

In this work, a novel crystal, (E)-4-(4-methylbenzyl)-6-styrylpyridazin-3(2H)-one (E-BSP) was synthesized via Knoevenagel condensation of benzaldehyde and (E)-6-(4-methoxystyryl)-4,5-dihydropyridazin-3(2H)-one. The molecular structure of E-BSP was confirmed by using FT-IR, 1H-NMR, 13C-NMR, UV-vis, ESI-MS, TGA/DTA thermal analyses and single crystal X-ray diffraction. The DFT/B3LYP methods with the 6-311++G(d,p) basis set were used to determine the vibrational modes over the optimized structure. Potential energy distribution (PED) and the VEDA 4 software were used to establish the theoretical mode assignments. The same approach was used to compute the energies of frontier molecular orbitals (HOMO-LUMO), global reactivity descriptors, and molecular electrostatic potential (MEP). Additionally, experimental and computed UV spectral parameters were determined in methanol and the obtained outputs were supported by FMO analysis. Molecular docking and molecular dynamics (MD) simulation analyses of the E-BSP against six proteins obtained from different cancer pathways were carried out. The proteins include; epidermal growth factor receptor (EGFR), Estrogen receptor (ERα), Mammalian target of rapamycin (mTOR), Progesterone receptor (PR) (Breast cancer), Human cyclin-dependent kinase 2 (CDK2) (Colorectal cancer), and Survivin (Squamous cell carcinoma/Non-small cell lung cancer). The results of the analyses showed that the compound had less binding energies ranging between -6.30 to -9.09 kcal/mol and formed stable complexes at the substrate-binding site of the proteins after the 50 ns MD simulation. Therefore, E-BSP was considered a potential inhibitor of different cancer pathways and should be used for the treatment of cancer after experimental validation and clinical trial.Communicated by Ramaswamy H. Sarma.

A Natural Dihydropyridazinone Scaffold Generated from a Unique Substrate for a Hydrazine-Forming Enzyme

Nitrogen-nitrogen bond-containing functional groups are rare, but they are found in a considerably wide class of natural products. Recent clarifications of the biosynthetic routes for such functional groups shed light onto overlooked biosynthetic genes distributed across the bacterial kingdom, highlighting the presence of yet-to-be identified natural products with peculiar functional groups. Here, the genome-mining approach targeting a unique hydrazine-forming gene led to the discovery of actinopyridazinones A (1) and B (2), the first natural products with dihydropyridazinone rings. The structure of actinopyridazinone A was unambiguously established by total synthesis. Biosynthetic studies unveiled the structural diversity of natural hydrazines derived from this family of N-N bond-forming enzymes.

Anti-inflammatory activity of pyridazinones: A review

The pyridazinone core has emerged as a leading structure for fighting inflammation, with low ulcerogenic effects. Moreover, easy functionalization of various ring positions of the pyridazinone core structure makes it an attractive synthetic and therapeutic target for the design and synthesis of anti-inflammatory agents. The present review surveys the recent advances of pyridazinone derivatives as potential anti-inflammatory agents to provide insights into the rational design of more effective anti-inflammatory pyridazinones.

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.

Pyridazinone Derivatives Limit Osteosarcoma-Cells Growth In Vitro and In Vivo

Simple Summary

There is a dire need for novel therapeutic interventions to treat osteosarcoma. Pyridazinone derivatives have proven some efficacy in several cancer models, but their effect on osteosarcoma is yet to be evaluated. Our goal was to synthesize and evaluate, both in vitro and in vivo, some pyridazinone derivatives to provide a proof of concept of their potential as anti-osteosarcoma molecules. We demonstrated that our newly synthesized pyridazinone scaffold-based molecules might be hit-candidates to develop new therapeutic avenues for multi-therapy purposes.

Abstract

Osteosarcoma is a rare primary bone cancer that mostly affects children and young adults. Current therapeutic approaches consist of combining surgery and chemotherapy but remain unfortunately insufficient to avoid relapse and metastases. Progress in terms of patient survival has remained the same for 30 years. In this study, novel pyridazinone derivatives have been evaluated as potential anti-osteosarcoma therapeutics because of their anti-type 4 phosphodiesterase activity, which modulates the survival of several other cancer cells. By using five—four human and one murine osteosarcoma—cell lines, we demonstrated differential cytotoxic effects of four pyridazinone scaffold-based compounds (mitochondrial activity and DNA quantification). Proapoptotic (annexin V positive cells and caspase-3 activity), anti-proliferative (EdU integration) and anti-migratory effects (scratch test assay) were also observed. Owing to their cytotoxic activity in in vitro conditions and their ability to limit tumor growth in a murine orthotopic osteosarcoma model, our data suggest that these pyridazinone derivatives might be hit-candidates to develop new therapeutic strategies against osteosarcoma.

Catalytic Asymmetric (3 + 3) Cycloaddition of Oxyallyl Zwitterions with α-Diazomethylphosphonates

The unique structure of oxyallyls represents a significant challenge for their catalytic asymmetric applications. Herein, an unprecedented chiral imidodiphosphoric acid-catalytic enantioselective (3 + 3) cycloaddition between oxyallyl zwitterions generated in situ from α-haloketones and α-diazomethylphosphonates was developed. Pharmaceutically interesting chiral pyridazine-4(1H)-ones were obtained in up to 98% yields with excellent stereoselectivities (up to 99% ee, > 99:1 dr).

Pyridazinones containing dithiocarbamoyl moieties as a new class of selective MAO-B inhibitors

A novel class of potential MAO-B inhibitors was designed and synthesized in good yield by combining the pyridazinone moiety with the dithiocarbamate framework, two relevant pharmacophores for drug discovery. The biological results obtained for the different pyridazinone/dithiocarbamate hybrids (compounds 8-14) indicated that most of them reversibly and selectively inhibit the hMAO-B in vitro with IC₅₀ values in the µM range and exhibit not significant cellular toxicity. The analogues 9a₁, 11a₁, 12a₂, 12b₁ and 12b₂, which present the dithiocarbamate fragment derivatized with a piperidin-1-yl or pyrrolidin-1-yl group and placed at C3 or C4 of the diazine ring, were the most attractive compounds of these series. Molecular modeling studies were performed to analyze the binding mode to the enzyme and the structure activity relationships of the titled compounds, as well as to predict their drug-like properties.

Novel Ring Systems: Spiro[Cycloalkane] Derivatives of Triazolo- and Tetrazolo-Pyridazines

In orderto synthesize new pyridazine derivatives anellated with different nitrogen heterocyclic moieties, spiro[cycloalkane]pyridazinones were transformed into the corresponding thioxo derivatives via a reaction with phosphorus pentasulfide. The reaction of the formed 2,3-diazaspiro[5.5]undec-3-ene-1-thiones with hydrazine provided the corresponding 1-hydrazono-2,3-diazaspiro[5.5]undec-3-ene, whose diazotization led to the desired spiro[cyclohexane-1,8′-tetrazolo[1,5-b]pyridazines. The reaction of dihydropyridazinethiones with benzhydrazide afforded the corresponding 7H-spiro[[1,2,4]triazolo[4,3-b]pyridazin-8,1′-cyclohexanes]. As a result of our work, seven new pyridazinethione intermediates were prepared, which served as starting materials for the synthesis of two kinds of new ring systems: tetrazolo-pyridazines and triazolo-pyridazines. The six new annulated derivatives were characterized by physicochemical parameters. The new N-heterocycles are valuable members of the large family of pyridazines.

Synthesis, spectroscopy, crystal structure, TGA/DTA study, DFT and molecular docking investigations of (E)-4-(4-methylbenzyl)-6-styrylpyridazin-3(2H)-one

In this study, we present the synthesis of novel pyridazin-3(2H)-one derivative namely (E)-4-(4-methylbenzyl)-6-styrylpyridazin-3(2H)-one (MBSP). The chemical structure of MBSP was characterized using spectroscopic techniques such as FT-IR, 1H NMR, 13C NMR, UV-Vis, ESI-MS, and finally, the structure was confirmed by single X-ray diffraction studies. The DFT calculation was performed to compare the gas-phase geometry of the title compound to the solid-phase structure of the title compound. Furthermore, a comparative study between theoretical UV-Vis, IR, 1H- and 13C NMR spectra of the studied compound and experimental ones have been carried out. The thermal behavior and stability of the compound were analyzed by using TGA and DTA techniques which revealed that the compound is thermostable up to its melting point. Finally, the in silico docking and ADME studies are performed to investigate whether MBSP is a potential therapeutic for COVID-19.

Synthesis, Cytotoxicity and Anti-Proliferative Activity Against AGS Cells of New 3(2H)-Pyridazinone Derivatives Endowed with a Piperazinyl Linker

Novel twenty-three 3(2H)-pyridazinone derivatives were designed and synthesized based on the chemical requirements related to the anti-proliferative effects previously demonstrated within this scaffold. The introduction of a piperazinyl linker between the pyridazinone nucleus and the additional (un)substituted phenyl group led to some compounds endowed with a limited cytotoxicity against human gingival fibroblasts (HGFs) and good anti-proliferative effects against gastric adenocarcinoma cells (AGS) as evaluated by MTT and LDH assays, using doxorubicin as a positive control. Successive analyses revealed that the two most promising representative compounds (12 and 22) could exert their effects by inducing oxidative stress as demonstrated by the hydrogen peroxide release and the morphological changes (cell blebbing) revealed by light microscopy analysis after the haematoxylin-eosin staining. Moreover, to further assess the apoptotic process induced by compounds 12 and 22, Bax expression was measured by flow cytometry. These findings enlarged our knowledge of the structural requirements in this scaffold to display valuable biological effects against cancerous cell lines.

Pyridazine as a privileged structure: An updated review on anticancer activity of pyridazine containing bioactive molecules

Identification of potent anticancer agents with high selectivity and low toxicity remains on the way to human health. Pyridazine featuring advantageous physicochemical properties and antitumor potential usually is regarded as a central core in numerous anticancer derivatives. There are several approved pyridazine-based drugs in the market and analogues currently going through different clinical phases or registration statuses, suggesting pyridazine as a promising drug-like scaffold. The current review is intended to provide a comprehensive and updated overview of pyridazine derivatives as potential anticancer agents. In particular, we focused on their structure-activity relationship (SAR) studies, design strategies, binding modes and biological activities in the hope of offering novel insights for further rational design of more active and less toxic anticancer drugs.

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.

New Spiro[cycloalkane-pyridazinone] Derivatives with Favorable Fsp3 Character

The large originator pharmaceutical companies need more and more new compounds for their molecule banks, because high throughput screening (HTS) is still a widely used method to find new hits in the course of the lead discovery. In the design and synthesis of a new compound library, important points are in focus nowadays: Lipinski’s rule of five (RO5); the high Fsp3 character; the use of bioisosteric heterocycles instead of aromatic rings. With said aim in mind, we have synthesized a small compound library of new spiro[cycloalkane-pyridazinones] with 36 members. The compounds with this new scaffold may be useful in various drug discovery projects.

New insights on the arylpiperazinylalkyl pyridazinone ET1 as potent antinociceptive and anti-inflammatory agent

Pyridazine derivatives, such as arylpiperazinylalkyl pyridazinones, display antinociceptive effects to thermal and chemical stimuli. Here, we extended our previous knowledge on the pharmacological profile of 4-amino-6-methyl-2-(3-(4-(4-methylcyclohexa-1,3-dien-1-yl)piperazin-1-yl)propyl)-5-vinylpyridazin-3(2H)-one, here referred as ET1, paving the way for the comprehension of its complete mechanism of action. To this aim, we have evaluated the mouse behavioural responses in several animal models of pain, the effect of ET1 in the murine model of zymosan-induced paw oedema and air-pouch, assessing the cytokines and the cellular phenotype and finally, an in vitro radioligand binding study was performed on a panel of 30 different receptors. In the formalin test, ET1 reduced both neurogenic and inflammatory phase of nociception induced by the aldehyde. Similarly, ET1 strongly reduced paw licking response in the capsaicin test, the abdominal stretching in the writhing test and the carrageenan-induced thermal hyperalgesia. ET1 also evoked a long-lasting reduction of thermal hyperalgesia. Furthermore, ET1 produced a long-lasting anti-inflammatory effect in the zymosan-induced mouse paw oedema and air-pouch through the selective inhibition of inflammatory monocytes recruitment and the modulation of IL-1β, IL-6, TNF-α and MCP-1. Binding experiments confirmed an inhibitory effect on adrenergic α_1A, α_1B and α_2A receptors subtypes and, for the first time, a moderate affinity was observed for the following receptors: histamine H₁, imidazoline I₂, sigma non-opioid intracellular receptor 1 and σ2. These results prompt ET1 as a potent analgesic and anti-inflammatory agent, and support the possibility that it may be suitable for clinical applications in a wide-range of inflammatory-based diseases.

[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.

Synthesis of Spiro[cycloalkane-pyridazinones] with High Fsp3 Character

Background:

owadays, in course of the drug design and discovery much attention is paid to the physicochemical parameters of a drug candidate, in addition to their biological activity. Disadvantageous physicochemical parameters can hinder the success of a drug candidate.

Objective:

Lovering et al. introduced the Fsp3 character as a measure of carbon bond saturation, which is related to the physicochemical paramethers of the drug. The pharmaceutical research focuses on the synthesis of compounds with high Fsp3 character.

Methods:

To improve the physicochemical properties (clogP, solubility, more advantageous ADME profile, etc.) of drug-candidate molecules one possibility is the replacement of all-carbon aromatic systems with bioisoster heteroaromatic moieties, e.g. with one or two nitrogen atom containing systems, such as pyridines and pyridazines, etc. The other option is to increase the Fsp3 character of the drug candidates. Both of these aspects were considered in the design the new spiro[cycloalkanepyridazinones], the synthesis of which is described in the present study.

Results:

Starting from 2-oxaspiro[4.5]decane-1,3-dione or 2-oxaspiro[4.4]nonane-1,3-dione, the corresponding ketocarboxylic acids were obtained by Friedel-Crafts reaction with anisole or veratrole. The ketocarboxylic acids were treated by hydrazine, methylhydrazine or phenylhydrazine to form the pyridazinone ring. N-Alkylation reaction of the pyridazinones resulted in the formation of further derivatives with high Fsp3 character.

Conclusion:

A small compound library was obtained incorporating compounds with high Fsp3 characters, which predicts advantageous physico-chemical parameters (LogP, ClogP and TPSA) for potential applications in medicinal chemistry.

Synthesis, molecular modelling and biological activity of some pyridazinone derivatives as selective human monoamine oxidase-B inhibitors

BACKGROUND

Since brain neurotransmitter levels are associated with the pathology of various neurodegenerative diseases like Parkinson and Alzheimer, monoamineoxidase (MAO) plays a critical role in balancing these neurotransmitters in the brain. MAO isoforms appear as promising drug targets for the development of central nervous system agents. Pyridazinones have a broad array of biological activities. Here, six pyridazinone derivatives were synthesized and their human monoamine oxidase inhibitory activities were evaluated by molecular docking studies, in silico ADME prediction and in vitro biological screening tests.

METHODS

The compounds were synthesized by the reaction of different piperazine derivatives with 3 (2H)-pyridazinone ring and MAO-inhibitory effects were investigated. Docking studies were conducted with Maestro11.8 software.

RESULTS

Most of the synthesized compounds inhibited hMAO-B selectively except compound 4f. Compounds 4a-4e inhibited hMAO-B selectively and reversibly in a competitive mode. Compound 4b was found as the most potent (k_i = 0.022 ± 0.001 µM) and selective (SI (Ki _{hMAO-A/hMAO-B}) = 206.82) hMAO-B inhibitor in this series. The results of docking studies were found to be consistent with the results of the in vivo activity studies. Compounds 4a-4e were found to be non-toxic to HepG2 cells at 25 μM concentration. In silico calculations of ADME properties indicated that the compounds have good pharmacokinetic profiles.

CONCLUSION

It was concluded that 4b is possibly recommended as a promising nominee for the design and development of new pyridazinones which can be used in the treatment of neurological diseases.

Polymorphism of 2-(5-benzyl-6-oxo-3-phenyl-1,6-di-hydro-pyridazin-1-yl)acetic acid with two monoclinic modifications: crystal structures and Hirshfeld surface analyses

Two polymorphs of the title compound, C19H16N2O3, were obtained from ethano-lic (polymorph I) and methano-lic solutions (polymorph II), respectively. Both polymorphs crystallize in the monoclinic system with four formula units per cell and a complete mol-ecule in the asymmetric unit. The main difference between the mol-ecules of (I) and (II) is the reversed position of the hy-droxy group of the carb-oxy-lic function. All other conformational features are found to be similar in the two mol-ecules. The different orientation of the OH group results in different hydrogen-bonding schemes in the crystal structures of (I) and (II). Whereas in (I) inter-molecular O-H⋯O hydrogen bonds with the pyridazinone carbonyl O atom as acceptor generate chains with a C(7) motif extending parallel to the b-axis direction, in the crystal of (II) pairs of inversion-related O-H⋯O hydrogen bonds with an R 2 2(8) ring motif between two carb-oxy-lic functions are found. The inter-molecular inter-actions in both crystal structures were analysed using Hirshfeld surface analysis and two-dimensional fingerprint plots.

Crystal structure, Hirshfeld surface analysis and DFT studies of 2-[5-(4-methyl-benz-yl)-6-oxo-3-phenyl-1,6-di-hydro-pyridazin-1-yl]acetic acid

The title pyridazinone derivative, C20H18N2O3, is not planar. The phenyl ring and the pyridazine ring are inclined to each other by 10.55 (12)°, whereas the 4-methyl-benzyl ring is nearly orthogonal to the pyridazine ring, with a dihedral angle of 72.97 (10)°. In the crystal, mol-ecules are linked by pairs of O-H⋯O hydrogen bonds, forming inversion dimers with an R 2 2(14) ring motif. The dimers are linked by C-H⋯O hydrogen bonds, generating ribbons propagating along the c-axis direction. The inter-molecular inter-actions were additionally investigated using Hirshfeld surface analysis and two-dimensional fingerprint plots. They revealed that the most significant contributions to the crystal packing are from H⋯H (48.4%), H⋯O/O⋯H (21.8%) and H⋯C/C⋯H (20.4%) contacts. Mol-ecular orbital calculations providing electron-density plots of HOMO and LUMO mol-ecular orbitals and mol-ecular electrostatic potentials (MEP) were also computed, both with the DFT/B3LYP/6-311 G++(d,p) basis set.

Crystal structure, Hirshfeld surface analysis and DFT studies of 6-[(E)-2-(thio-phen-2-yl)ethenyl]-4,5-di-hydro-pyridazin-3(2H)-one

In the title compound, C10H10N2OS, the five atoms of the thio-phene ring are essentially coplanar (r.m.s. deviation = 0.0037 Å) and the pyridazine ring is non-planar. In the crystal, pairs of N-H⋯O hydrogen bonds link the mol-ecules into dimers with an R 2 2(8) ring motif. The dimers are linked by C-H⋯O inter-actions, forming layers parallel to the bc plane. The theoretical geometric parameters are in good agreement with XRD results. The inter-molecular inter-actions were investigated using a Hirshfeld surface analysis and two-dimensional fingerprint plots. The Hirshfeld surface analysis of the title compound suggests that the most significant contributions to the crystal packing are by H⋯H (39.7%), C⋯H/H⋯C (17.3%) and O⋯H/H⋯O (16.8%) contacts.

Crystal structure and Hirshfeld surface analysis of (E)-6-(4-hy-droxy-3-meth-oxy-styr-yl)-4,5-di-hydro-pyridazin-3(2H)-one

In the title com-pound, C13H14N2O3, the dihydropyridazine ring (r.m.s. deviation = 0.166 Å) has a screw-boat conformation. The dihedral angle between its mean plane and the benzene ring is 0.77 (12)°. In the crystal, inter-molecular O-H⋯O hydrogen bonds generate C(5) chains and N-H⋯O hydrogen bonds produce R 2 2(8) motifs. These types of inter-actions lead to the formation of layers parallel to (12). The three-dimensional network is achieved by C-H⋯O inter-actions, including R 2 4(8) motifs. Inter-molecular inter-actions were additionally investigated using Hirshfeld surface analysis and two-dimensional fingerprint plots. The most significant contributions to the crystal packing are by H⋯H (43.3%), H⋯C/C⋯H (19.3%), H⋯O/H⋯O (22.6%), C⋯N/N⋯C (3.0%) and H⋯N/N⋯H (5.8%) contacts. C-H⋯π inter-actions and aromatic π-π stacking inter-actions are not observed.

Crystal structures and Hirshfeld surface analyses of 4-benzyl-6-phenyl-4,5-di-hydro-pyridazin-3(2H)-one and methyl 2-[5-(2,6-di-chloro-benz-yl)-6-oxo-3-phenyl-1,4,5,6-tetra-hydropyridazin-1-yl]acetate

The asymmetric units of the title compounds both contain one nonplanar mol-ecule. In 4-benzyl-6-phenyl-4,5-di-hydro-pyridazin-3(2H)-one, C17H14N2O, (I), the phenyl and pyridazine rings are twisted with respect to each other, making a dihedral angle of 46.69 (9)°; the phenyl ring of the benzyl group is nearly perpendicular to the plane of the pyridazine ring, the dihedral angle being 78.31 (10)°. In methyl 2-[5-(2,6-di-chloro-benz-yl)-6-oxo-3-phenyl-1,4,5,6-tetra-hydropyridazin-1-yl]acetate, C20H16Cl2N2O3, (II), the phenyl and pyridazine rings are twisted with respect to each other, making a dihedral angle of 21.76 (18)°, whereas the phenyl ring of the di-chloro-benzyl group is inclined to the pyridazine ring by 79.61 (19)°. In the crystal structure of (I), pairs of N-H⋯O hydrogen bonds link the mol-ecules into inversion dimers with an R 2 2(8) ring motif. In the crystal structure of (II), C-H⋯O hydrogen bonds generate dimers with R 1 2(7), R 2 2(16) and R 2 2(18) ring motifs. The Hirshfeld surface analyses of compound (I) suggests that the most significant contributions to the crystal packing are by H⋯H (48.2%), C⋯H/H⋯C (29.9%) and O⋯H/H⋯O (8.9%) contacts. For compound (II), H⋯H (34.4%), C⋯H/H⋯C (21.3%) and O⋯H/H⋯O (16.5%) inter-actions are the most important contributions.