Synthesis of Pyridazine Derivatives via Aza-Diels-Alder Reactions of 1,2,3-Triazine Derivatives and 1-Propynylamines

Diazotization of o-Aminoamidoximes for the Preparation of Energetic 6,5,6-Fused 1,2,3-Triazine-3-oxides

Two 6,5,6-fused 1,2,3-triazine-3-oxides (4 and 6) were designed and synthesized via the reaction of o-aminoamidoximes with sodium nitrite. In addition, the ring-opening products (5, 7, and 8) derived from 1,2,3-triazine-3-oxides were isolated and characterized. A comprehensive exploration of the reaction mechanism governing the ring-opening process was performed through a combination of theoretical and experimental studies. Notably, compound 4 exhibited commendable detonation properties and low sensitivity, demonstrating its promising potential as an energetic material.

Evaluation of Novel Spiro-pyrrolopyridazine Derivatives as Anticancer Compounds: In Vitro Selective Cytotoxicity, Induction of Apoptosis, EGFR Inhibitory Activity, and Molecular Docking Analysis

Cancer, characterized by uncontrolled cell proliferation, remains a global health challenge. Despite advancements in cancer treatment, drug resistance and adverse effects on normal cells remain challenging. The epidermal growth factor receptor (EGFR), a transmembrane tyrosine kinase protein, is crucial in controlling cell proliferation and is implicated in various cancers. Here, the cytotoxic and apoptotic potential of 21 newly synthesized spiro-pyrrolopyridazine (SPP) derivatives was investigated on breast (MCF-7), lung (H69AR), and prostate (PC-3) cancer cells. XTT assay was used for cytotoxicity assessment. Flow cytometry and western blot (WB) analyses were conducted for apoptosis detection. Additionally, the EGFR inhibitory potential of these derivatives was evaluated via a homogeneous time-resolved fluorescence (HTRF) assay, and WB and molecular docking studies were conducted to analyze the binding affinities of SPP10 with EGFR. SPPs, especially SPP10, exhibit significant cytotoxicity across MCF-7, H69AR, and PC-3 cancer cells with IC50 values of 2.31 ± 0.3, 3.16 ± 0.8, and 4.2 ± 0.2 μM, respectively. Notably, SPP10 demonstrates selective cytotoxicity against cancer cells with a low impact on nontumorigenic cells (IC50 value: 26.8 ± 0.4 μM). Flow cytometric analysis demonstrated the potent induction of apoptotic cell death by SPP10 in all of the tested cancer cells. Western blot analysis revealed the involvement of key apoptotic proteins, with SPP10 notably inhibiting antiapoptotic Bcl-2 while inducing pro-apoptotic Bax and cytochrome c. SPP10 exhibited significant EGFR kinase inhibitory activity, surpassing the efficacy of the reference drug erlotinib. Molecular docking studies support these findings, revealing strong binding affinities of SPP10 with both wild-type and mutated EGFR. The study underscores the significance of heterocyclic compounds, particularly spiro-class heterocyclic molecules, in advancing cancer research. Overall, SPP10 emerges as a promising candidate for further investigations in cancer treatment, combining potent cytotoxicity, apoptotic induction, and targeted EGFR inhibition.

Pyridazine derivatives as selective COX-2 inhibitors: A review on recent updates

Selective cyclooxygenase (COX)-2 inhibitors have several advantages over nonselective COX inhibitors (nonsteroidal anti-inflammatory drugs [NSAIDs]), including the absence of adverse effects (renal and hepatic disorders) associated with the long-term use of standard NSAIDs, as well as an improved gastrointestinal profile. The pyridazine nucleus is regarded as a promising scaffold for the development of powerful COX-2 inhibitors, particularly when selectively functionalized. This article summarizes some methods for the synthesis of pyridazine derivatives. Furthermore, it covers all of the pyridazine derivatives that have appeared as selective COX-2 inhibitors, making it useful as a reference for the rational design of novel selective COX-2 inhibitors.

Copper-catalysed dehydrogenative self-coupling/cyclization of 5-aminopyrazoles: synthesis and photophysical study of pyridazines

An interesting self-coupling/cyclization of 5-aminopyrazoles is revealed, which provides a variety of pyridazine cores in reasonable yields. In this reaction, C(sp²)-C(sp²) and N-N bond formation occurs simultaneously in one reaction vessel. The photophysical properties of the synthesized compounds were also studied and some of them exhibited fluorescence properties with good quantum yields. A radical mediated reaction mechanism is proposed with the help of control experiments.

Photoinduced Decarbonylative Rearrangement of Diazabicyclo[2.2.2]Octenones: A Photochemical Approach of Diazabicyclo[4.1.0]heptene Skeleton from Masked o-Benzoquinone

We report a photoinduced decarbonylative rearrangement of diazabicyclo[2.2.2]octenone in the facile synthesis of a functionalized diazabicyclo[4.1.0]heptene skeleton, a unique derivative of the hydropyridazine type structure which could be found in a variety of biologically active natural products. The scope of functional group compatibility in the photoreaction was examined by taking advantage of the easy access of the heterobicyclo[2.2.2] structure from the Diels-Alder reaction of masked o-benzoquinones. 4-Phenyl-1,2,4-triazoline-3,5-dione served as the dienophile which provided the adjacent N-N unit in hexahydropyridazine-type products of subsequent photorearrangement.

Triazines: Syntheses and Inverse Electron-demand Diels-Alder Reactions

Triazines are an important class of six-membered aromatic heterocycles possessing three nitrogen atoms, resulting in three types of regio-isomers: 1,2,4-triazines (a-triazines), 1,2,3-triazines (v-triazines), and 1,3,5-triazines (s-triazines). Notably, the application of triazines as cyclic aza-dienes in inverse electron-demand Diels-Alder (IEDDA) cycloaddition reactions has been established as a unique and powerful method in N-heterocycle synthesis, natural product preparation, and bioorthogonal chemistry. In this review, we comprehensively summarize the advances in the construction of these triazines via annulation and ring-expansion reactions, especially emphasizing recent developments and challenges. The synthetic transformations of triazines are focused on IEDDA cycloaddition reactions, which have allowed access to a wide scope of heterocycles, including pyridines, carbolines, azepines, pyridazines, pyrazines, and pyrimidines. The utilization of triazine IEDDA reactions as key steps in natural product synthesis is also discussed. More importantly, a particular attention is paid on the bioorthogonal application of triazines in fast click ligation with various strained alkenes and alkynes, which opens a new opportunity for studying biomolecules in chemical biology.