Design, Synthesis, and Structure–Activity Relationships of a Novel Series of 5-Alkylidenepyridazin-3(2H)-ones with a Non-cAMP-Based Antiplatelet Activity

Design, synthesis, and biological evaluation of some new 2-phenyl-3,6-pyridazinedione derivatives as PDE-5 inhibitors

Various 2-phenyl-3,6-pyridazinedione derivatives 4a-j, 5a-c, 6a,b, 7a-c, 8, 9, 10a-d, and 11a-d, were effectivelysynthesized, and tested for their potential inhibition of phosphodiesterase enzyme at 10 µM. Then fourteen compounds exhibiting the highest inhibition 4b, 4d, 4e, 4g, 4h, 4i, 5a, 6a,b, 7c, 10a,b, 11a, and 11d were selected for screening their PDE-5 inhibition, where compounds 4b,g,h, and 11a revealed promising PDE-5 inhibition having IC50 values = 25, 53, 22, and 42 nM, respectively in comparison with Sildenafil (IC50 = 16 nM). Additionally, these four most active compounds were safe to normal fibroblast cell line WI-38. Moreover, 4f, 4h, 4j, 10d, and 11d had almost the same anti-proliferative effect against the aortic cell line as Sildenafil. Furthermore, molecular docking illustrated that the binding of the target compounds with the key amino acids in the binding site of PDE-5 (PDB 2H42) was like to that of the cocrystallized ligand Sildenafil. Additionally, molecular dynamics simulation for the most active compound 4h revealed high stability of the 4h -PDE5 complex explaining its promising activity as a PDE-5 inhibitor. Therefore, the 2-phenyl-3,6-pyridazinedione scaffold can be considered an important core for designing more promising PDE-5 inhibitors.

Synthesis of Tetrasubstituted 1,4-Dicarbonyl (Z)-2,3-Dihaloalkenes via Electrophilic Halogenation of Alkynyl Hydrazones

A highly practical and stereoselective route to 1,4-dicarbonyl 2,3-dihaloalkenes is presented. The strategy involves bench-stable unprotected alkynyl hydrazones and commercially available N-halosuccinimides that provide γ-oxo-α,β-(Z)-dihaloenoates in excellent yields with complete Z-selectivity. The protocol also furnishes vicinal dihaloalkenes with two different halogen atoms. Also, a straightforward one-pot synthesis of dihaloenoates from readily accessible 2-oxo-3-butynoate is demonstrated. In addition, potential synthetic transformations of 4-oxo-2,3-dibromoenoates are explored, which include the synthesis of valuable five- and six-membered heterocycles.

Synthesis and vasodilator activity of some pyridazin-3(2H)-one based compounds

Aim: Hypertension is a major health problem worldwide resulting in high death rates due to its consequences and complications. Therefore, searching for new vasorelaxants is a must to find new vasodilators efficient for the treatment of different cardiovascular diseases. Methodology: Different 6-phenyl-3-pyridazinone based derivatives were synthesized and screened for their vasorelaxant activity according to the reported method using hydralazine as a standard. Results: The tested compounds revealed potent to mild activity with EC50 values 0.339–114.300 μM compared with hydralazine EC50 = 18.210 μM. Conclusion: The most active compounds were the acid 5, its ester analog 4 and 4-methoxyphenylhydrazide derivative 10c (EC50 = 0.339, 1.225 and 1.204 μM, respectively). Therefore, 6-phenylpyridazin-3(2 H)-one can be a hit for structural optimization to obtain promising vasorelaxants.

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.

5-[(tert-Butyl-diphenyl-sil-yloxy)meth-yl]pyridazin-3(2H)-one

In the title compound, C₂₁H₂₄N₂O₂Si, a new pyridazin-3(2H)-one derivative, the carbonyl group of the heterocyclic ring and the O atom of the silyl ether are located on the same side of the pyridazinone ring and the C—C—O—Si torsion angle is −140.69 (17)°. In the crystal, mol­ecules are linked by pairs of strong N—H⋯O hydrogen bonds into centrosymmetric dimers with graph-set notation R₂²(8). Weak C—H⋯π inter­actions are also observed.

Synthesis and complete assignment of the 1H and 13C NMR spectra of 6-substituted and 2,6-disubstituted pyridazin-3(2H)-ones

Several pyridazin-3(2H)-one derivatives were synthesized starting from alkyl furans using oxidation with singlet oxygen to give 4-methoxy or 4-hydroxybutenolides, key intermediates of the synthetic strategy followed. For all pyridazinones reported, a complete assignment of the (1)H and (13)C NMR spectra using one- and two-dimensional NMR spectroscopic methods, which included NOE, DEPT, COSY, HSQC and HMBC experiments, was accomplished. Correlations between the chemical shifts of the heterocyclic ring atoms and substituents at N-2 and C-6 were analyzed.

Methyl 4-{[6-(4-bromo-phen-yl)-3-oxo-2,3,4,5-tetra-hydro-pyridazin-4-yl]methyl}benzoate

The structure of the title compound, C₁₉H₁₇BrN₂O₃, consists of two cyclic groups, viz. 4-(meth­oxy­carbon­yl)phenyl and 6-(4-bromo­phen­yl)-3-oxo-2,3,4,5-dihydro­pyridazin-4-yl, which are linked by a methyl­ene spacer. The pyridazine ring is twisted and the dihedral angle between its mean plane and that of the bromo­phenyl mean plane is 17.2 (2)°. The 4-(meth­oxy­carbon­yl)phenyl group shows a quasi-planar conformation, where the dihedral angle between the mean planes of the phenyl ring and carboxyl­ate ester group is 7.9 (4)°. Centrosymmetric inter­molecular N—H⋯O hydrogen bonds form dimers. These are linked by C—Br⋯O=C inter­actions [Br⋯O = 3.10 (1) Å] to form a one-dimensional polymeric structure running along the [10] direction.

Silica-supported aluminum chloride-assisted solution phase synthesis of pyridazinone-based antiplatelet agents

A solution phase protocol that enabled the synthesis of three diverse libraries of pyridazin-3-ones incorporating α,β-unsaturated moieties at position 5 of the heterocyclic core has been developed using silica-supported aluminum trichloride as a heterogeneous and reusable catalyst. This robust procedure has facilitated the hit to lead process for these series of compounds and allowed the identification of new potent derivatives that elicit antiplatelet activity in the low micromolar range.