I2-Mediated Oxidative C–N and N–S Bond Formation in Water: A Metal-Free Synthesis of 4,5-Disubstituted/N-Fused 3-Amino-1,2,4-triazoles and 3-Substituted 5-Amino-1,2,4-thiadiazoles

Structural modification strategies of triazoles in anticancer drug development

The triazole functional group plays a pivotal role in the composition of biomolecules with potent anticancer activities, including numerous clinically approved drugs. The strategic utilization of the triazole fragment in the rational modification of lead compounds has demonstrated its ability to improve anticancer activities, enhance selectivity, optimize pharmacokinetic properties, and overcome resistance. There has been significant interest in triazole-containing hybrids in recent years due to their remarkable anticancer potential. However, previous reviews on triazoles in cancer treatment have failed to provide tailored design strategies specific to these compounds. Herein, we present an overview of design strategies encompassing a structure-modification approach for incorporating triazoles into hybrid molecules. This review offers valuable references and briefly introduces the synthesis of triazole derivatives, thereby paving the way for further research and advancements in the field of effective and targeted anticancer therapies.

Synthesis of 3,4,5-Trisubstituted 1,2,4-Triazoles via I2-Catalyzed Cycloaddition of Amidines with Hydrazones

A general and practical method for the construction of various 3,4,5-trisubstituted 1,2,4-triazoles via I2-catalyzed cycloaddition of N-functionalized amidines with hydrazones is reported. This strategy features cheap and readily available catalyst and starting materials, broader substrate scope, and moderate-to-good yields. The mechanism study shows that the existence of hydrogen on the nitrogen of hydrazones is crucial for this transformation.

Sodium Carbonate-Promoted Formation of 5-Amino-1,2,4-thiadiazoles and 5-Amino-1,2,4-selenadiazoles with Elemental Sulfur and Selenium

Sodium carbonate-promoted facile synthesis of 5-amino-1,2,4-thiadiazoles and 5-amino-1,2,4-selenadiazoles with elemental sulfur and selenium, respectively, was developed. This method was carried out with O2 in the air as the green oxidant, and it has several advantages, including low cost, low toxicity, and stable sulfur and selenium sources, good to excellent yields with water as the sole byproduct, simple operation, and a broad substrate scope. Preliminary mechanistic studies indicate that the formation of the 1,2,4-thiadiazole ring and the 1,2,4-selenadiazole ring undergoes different processes.

Base-promoted one-pot three-component desulphurization cross-coupling access to 4-cyanoimidazole

A novel, straightforward, and scalable base-mediated one-pot three-component desulphurization cross-coupling strategy is reported for the synthesis of 4-cyanoimidazole derivatives. Over 35 examples are provided and achieved yields exceeding 85%. Notably, the majority of these readily available compounds can be isolated through simple filtration, thereby circumventing the need for laborious column chromatography. Besides, the present protocol can be scaled up to 10 mmol with a yield of 87%, demonstrating promising potential for industrial applications.

Iodine-Catalyzed Synthesis of Benzo-β-carbolines through Desulfurative Cyclization of 2-(1H-Indol-3-ylsulfanyl)-phenylamines with Aryl Methyl Ketones

A novel transition metal-free strategy for the synthesis of benzene-fused β-carboline scaffolds has been developed. This protocol offers a rapid and direct pathway to access the benzene fused β-carboline from 2-(1H-indol-3-ylsulfanyl)-phenylamines and aryl methyl ketones using an efficient catalytic system of I2/DMSO. The present mild protocol proceeds through the sequential reactions of Kornblum oxidation, Pictet-Spengler cyclization, and desulfurization to afford the desired products in excellent yields up to 99%. Moreover, this method has a wide range of substrate tolerance and is operationally simple and applicable in gram-scale synthesis.

Nucleophilic Addition/Electrocyclization Strategy toward Polyheterocyclic-Fused Quinoline-2-thiones in Green Solvent

A metal-free and base-free cyclization reaction of ortho-heteroaryl anilines with isothiocyanatobenzene for the synthesis of diverse polyheterocyclic-fused quinoline-2-thiones was developed in PEG-200. This protocol features green solvent, lack of requirement for a metal and base, short reaction time consumption, and facile isolation via simple filtration. Furthermore, this protocol is easy to scale up which demonstrates outstanding synthetic scalability.

Access to 3-Amino-[1,2,4]-triazolo Pyridines and Related Heterocycles via Electrochemically Induced Desulfurative Cyclization

An efficient, one-pot approach has been established for synthesizing a wide range of 3-amino-[1,2,4]-triazolo pyridines and related heterocycles from the electrochemically induced desulfurative cyclization of 2-hydrazinopyridines with isothiocyanates. The protocol allows for the formation of C-N bonds under simple conditions without transition metals or external oxidants. The practicability of this strategy is demonstrated by its broad substrate scope, good functional group compatibility, and gram-scale synthesis. The late-stage modification of 3-amino-[1,2,4]-triazolo pyridines enables us to obtain several molecules with potent anticancer activity.

External oxidant-free and transition metal-free synthesis of 5-amino-1,2,4-thiadiazoles as promising antibacterials against ESKAPE pathogen strains

A new route to 5-amino-1,2,4-thiadiazole derivatives via reaction of N-chloroamidines with isothiocyanates has been proposed. The advantages of this method are high product yields (up to 93%), the column chromatography-free workup procedure, scalability and the absence of additive oxidizing agents or transition metal catalysts. The 28 examples of 5-amino-1,2,4-thiadiazole derivatives obtaining via the proposing protocol were evaluated in vitro against ESKAPE pathogens strains (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter cloacae). It was found that compounds 5ba, 5bd, 6a, 6d and 6c have potent antibacterial activity (MIC values 0.09-1.5 μg mL^-1), which is superior to the activity of commercial antibiotics such as pefloxacin (MIC 4-8 μg mL^-1) and streptomycin (MIC 2-32 μg mL^-1). The additional cytotoxic assay of hit compounds on PANC-1 cell line demonstrated the low or non-cytotoxicity activity at the same level of concentrations. Thus, these 5 compounds are promising starting point for further antimicrobial drug development.

Novel 1, 2, 4-Triazoles as Antifungal Agents

The development of innovative antifungal agents is essential. Some fungicidal agents are no longer effective due to resistance development, various side effects, and high toxicity. Therefore, the synthesis and development of some new antifungal agents are necessary. 1,2,4-Triazole is one of the most essential pharmacophore systems between five-membered heterocycles. The structure-activity relationship (SAR) of this nitrogen-containing heterocyclic compound showed potential antifungal activity. The 1,2,4-triazole core is present as the nucleus in a variety of antifungal drug categories. The most potent and broad activity of triazoles have confirmed them as pharmacologically significant moieties. The goal of this review is to highlight recent developments in the synthesis and SAR study of 1,2,4-triazole as a potential fungicidal compound. In this study, we provide the results of a biological activity evaluation using various structures and figures. Literature investigation showed that 1, 2, 4-triazole derivatives reveal the extensive span of antifungal activity. This review will assist researchers in the development of new potential antifungal drug candidates with high effectiveness and selectivity.

Toxicity of Ribavirin to Spodoptera litura by Inhibiting the Juvenile Hormone

Ribavirin is an antiviral drug showing high and delayed toxicity to the destructive agricultural pest Spodoptera litura. Larvae fed with artificial diets containing ribavirin could not molt successfully and showed abnormal phenotypes, including cuticle melanization and heavy wrinkle of the newly formed procuticle. RNA-Seq analysis suggested that ribavirin has great negative influence on cuticle. Quantitative real-time-polymerase chain reaction results indicated that ribavirin treatment decreased the expression of key genes in juvenile hormone (JH) biosynthesis (CYP15C1 and JH acid methyltransferase) and most cuticle protein genes, whereas the genes in melanin biosynthesis and bursicon genes were upregulated by ribavirin treatment. These results coincided with the decreased titer of JH I, JH II, and JH III determined by enzyme-linked immunosorbent assay, the much thinner procuticle layer exhibited by histopathological examination, and the cuticle melanization after ribavirin treatment. These results provided a valuable theoretical basis for the creation of green insecticides targeting JH and the development of new insecticide derivatives from 1,2,4-triazole.

Metal- and Oxidant-Free Green Three-Component Desulfurization and Deamination Condensation Approach to Fully Substituted 1H-1,2,4-Triazol-3-amines and Their Photophysical Properties

A metal- and oxidant-free three-component desulfurization and deamination condensation of amidines, isothiocyanates, and hydrazines for the synthesis of structurally diverse fully substituted 1H-1,2,4-triazol-3-amines is described. The reaction proceeds without the requirement of any external catalysts, metals, ligands, or oxidants. This [2 + 1 + 2] cyclization strategy involves C-N and C-S bond cleavage and the formation of new C-N bonds in one pot. This transformation provides a series of full substituted 1H-1,2,4-triazol-3-amines with advantages of a broad substrates scope, mild reaction conditions, environmental friendliness, and easy gram-scale applications. The fluorescence and aggregation-induced emission (AIE) properties of selected products were further tested. These synthesized 1H-1,2,4-triazol-3-amines may be worth investigating for further applications in the fields of organic chemistry, medicinal chemistry, and optical materials.

Iodine Catalyzed Oxidative Coupling of Diaminoazines and Amines for the Synthesis of 3,5-Disubstituted-1,2,4-Triazoles

A simple, convenient, transition metal-free one pot synthesis of 3,5-disubstituted-1,2,4-triazoles has been established. The innovation in this reaction is the use of easily available 1,1-diaminoazines as substrates. This method provides the products with wider substrate scope, at an expedited rate, and with relatively better yields in comparison to the reported methods. The reaction mechanism involves an initial intermolecular nucleophilic addition (facilitated by I₂) followed by intramolecular nucleophilic cyclization.

Revisiting applications of molecular iodine in organic synthesis

Molecular iodine contributes significantly to organic transformations in synthetic organic chemistry. It works effectively due to its mild Lewis acidic character, ability as an oxidizing agent, good moisture stability, and easy availability.

Design and synthesis of coumarin-triazole hybrids: biocompatible anti-diabetic agents, in silico molecular docking and ADME screening

The current study demonstrates the synthesis of coumarin-triazole hybrids 8 (a-e) in four steps starting from substituted salicylaldehyde 1 (a-e), and diethyl malonate 2. The spectroscopic studies provide the structure proofs of the new compounds, and the molecular structure of an intermediate 3a by crystallographic studies. The crystal structure analysis revealed the C–H...O, C–H... π, C–O...π and π...π molecular interactions. Further, the intermolecular interactions were quantified using Hirshfeld surface analysis and the DFT method B3LYP functional with 6–311++ G (d,p) basis set was employed to optimize the molecular geometry. The synthesized new coumarin-triazole hybrids, 8 (a–e) were screened for their α-amylase inhibitory potentials, and the results suggest that amongst the series, compounds 8c, and 8e show the promising inhibition of the enzyme, and might act as lead molecules for anti-diabetic activities. To understand the mode of action in silico molecular docking and ADME screening were performed.

Molecular Iodine-Promoted [3 + 2] Oxidative Cyclization for the Synthesis of Heteroarene-Fused [1,2,4] Thiadiazoles/Selenadiazoles

Two new classes of heteroarene-fused [1,2,4]thiadiazole and [1,2,4]selenadiazole are synthesized through the iodine-mediated [3 + 2] oxidative cyclization of 2-aminoheteroarenes and isothiocyanates/isoselenocyanates. This oxidative [3 + 2] annulation strategy is highly regiospecific to proceed a selective C-N bond formation at the endo-nitrogen of 2-aminoheteroarenes followed by an intramolecular oxidative N-S/N-Se bond formation. It is the first example of an I₂-mediated oxidative nitrogen-selenium (N-Se) bond formation.

Iodine-Catalyzed Regioselective Oxidative Cyclization of Aldehyde Hydrazones with Electron-Deficient Olefins for the Synthesis of Mefenpyr-Diethyl

A regioselective synthesis of polysubstituted dihydropyrazoles and pyrazoles through an iodine-catalyzed oxidative cyclization strategy of aldehyde hydrazones with electron-deficient olefins is described. The protocol adopts very mild reaction conditions and provides desirable yields. The reaction is supposed to proceed via a cascade C-H functionalization, C-N bond formation, and oxidation sequential processes. The overall simplicity and regioselectivity of the catalytic system make this approach a valuable and step-economical tool to construct a C-C bond for the synthesis of Mefenpyr-Diethyl.

I2-Catalyzed oxidative synthesis of N,4-disubstituted quinazolines and quinazoline oxides

An easy and efficient approach to the synthesis of N,4-disubstituted quinazoline-2-amine and oxides is described. This transformation proceeds smoothly in the presence of molecular iodine. The metal-free protocol presented here is insensitive to air moisture and operationally simple. This versatile and synthetic methodology is broadly applicable to a variety of N,4-disubstituted quinazoline-2-amines and oxides, which are synthesized in good to excellent yields starting from readily available inexpensive precursors.

Transition-metal-free S–N bond formation: synthesis of 5-amino-1,2,4-thiadiazoles from isothiocyanates and amidines

A novel and green method for the synthesis of 5-amino-1,2,4-thiadiazoles has been developed by the reaction of isothiocyanates with amidines.

Oxidative C(sp3)–H functionalization of methyl-azaheteroarenes: a facile route to 1,2,4-triazolo[4,3-a]pyridines

An oxidative [4 + 1] annulation for triazolo[4,3-a]pyridine–quinoline linked diheterocycle synthesis via functionalization of the sp³ C–H bonds of 2-methyl-azaheteroarenes has been developed.

Copper-Catalyzed Aerobic Oxidative [3+2] Annulation for the Synthesis of 5-Amino/Imino-Substituted 1,2,4-Thiadiazoles through C-N/N-S Bond Formation

A copper-catalyzed aerobic oxidative annulation reaction of 2-aminopyridine/amidine with isothiocyanate has been reported. This strategy involving C-N/N-S bond formations provides various 5-amino/imino-substituted 1,2,4-thiadiazole derivatives under a Cu/O₂ catalytic system. This method has demonstrated high reactivity, mild reaction conditions, and a broad substrate scope. Furthermore, the synthetic utilities of the approach are demonstrated by further modifications.