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This review focuses on the cytotoxic effect of new synthetic pyrazolo[4,3-e][1,2,4]triazine derivatives against different tumor cell lines. Some annulated pyrazolotriazines i.e., pyrazolo[4,3-e][1,2,4]triazolo[4,3-b][1,2,4]triazines and pyrazolo[4,3-e]tetrazolo[1,5-b][1,2,4]triazine demonstrated significant broad cytotoxic activity in micromolar range concentration, which could have excellent potential to be new candidate therapeutic agents in cancer chemotherapy.

A simple general synthesis of 1-aryl-6-azaisocytosine-5-carbonitriles 4 is described. This method is based on coupling diazonium salts with cyanoacetylcyanamide 2 and then cyclization of the formed 2-arylhydrazono-2-cyanoacetylcyanamides 3. The 6-azaisocytosines 4 were studied with respect to tautomeric equilibrium and the transformation of functional groups, and used in the synthesis of the condensed heterocyclic compounds: Purine isosteric imidazo[2,1-c]-[1,2,4]triazine 8 and the 1,2,4-triazino[2,3-a]quinazolines 9&ndash, 12.

The synthesis, the antitumor activity, the SAR and, whenever described, the possible mode of action of 1,2,4-triazine derivatives, their N-oxides, N,. N'-dioxides as well as the benzo- and hetero-fused systems are reported. Herein are treated derivatives disclosed to literature from the beginning of this century up to 2016. Among the three possible triazine isomers, 1,2,4-triazines are the most studied ones and many derivatives having remarkable antitumor activity have been reported in the literature and also patented reaching advanced phases of clinical trials.

In the title molecular salt, C5H9N4+·C13H10NO2−·C5H8N4, the asymmetric unit consists of a 6-amino-3,4-dimethyl-1,2,4-triazin-1-ium cation, a 2-anilinobenzoate anion and a neutral 3-amino-5,6-dimethyl-1,2,4-triazine molecule. The typical intramolecular N...H—O hydrogen bond is observed in the 2-anilinobenzoate anion. In the crystal, the protonated N atom and the 3-amino group are hydrogen bonded to the carboxylate oxygen atomsviaa pair of N—H...O hydrogen bonds, forming anR22(8) ring motif. These motifs are further linked with adjacent neutral 3-amino-5,6-dimethyl-1,2,4-triazine molecules by N—H...O and N—H...N hydrogen bonds to produce centrosymmetric six-membered units, enclosingR22(8) andR34(9) ring motifs. They are reinforced by a C—H...N hydrogen bond and stack up theb-axis direction.

Substituted 3,4-dihydro-1,8-naphthyridin-2(1H)-ones have been synthesized with the inverse electron-demand Diels–Alder reaction from 1,2,4-triazines bearing an acylamino group with a terminal alkyne side chain. Alkynes were first subjected to the Sonogashira cross-coupling reaction with aryl halides, the product of which then underwent an intramolecular inverse electron-demand Diels–Alder reaction to yield 5-aryl-3,4-dihydro-1,8-naphthyridin-2(1H)-ones by an efficient synthetic route.

On interacting α-bromoacetophenones with aromatic carboxylic acid hydrazides, the formation of two reaction products was observed in certain cases, the expected 1,2,4-triazine and the phenylglyoxal dihydrazone as an unexpected product. The effect of substituents in the initial substrates and of the conditions of carrying out the synthesis on the direction of the reaction have been studied. © 2013 Springer Science+Business Media New York.

The 'triazine' methodology for the synthesis of functionalized pyridine ligands proved to be a convenient method for the preparation of a luminescent Pt(II) complex. The key ligand can be assembled easily starting from readily accessible reagents. Further cycloplatination and post-functionalization led to the ready-to-go luminescent 'tag' 2 for peptide labeling. © 2012 Elsevier Ltd. All rights reserved.

A series of new 7-substitued-4H-1,3,4-thiadiazolo[2,3-c][1,2,4]- triazin-4-oneswere synthesized in good yields by the reaction of 4-amino-3- mercapto-1,2,4-triazin-5(4H)-one with various aromatic carboxylic acids in the presence of phosphorus oxychloride. All the synthesized compounds were confirmed by FT-IR, NMR (1H and 13C), ESI-MS spectroscopic techniques and analytical methods.

This paper presents a method for introducing toluene and bromobenzene moieties into 1,2,4-triazines as an alternative to cross-coupling reactions. It is demonstrated that the C=N bond of a wide range of 1,2,4-triazines undergoes addition of arenes in the presence of AlCl3. © 2014 Verlag der Zeitschrift für Naturforschung.

WOS: 000344472600001, PubMed ID: 25438754, A series of 1,2,4-triazine derivatives bearing piperazine amide moiety has been synthesized and investigated for their potential anticancer activities. 1-[4-(5,6-Bis(4-subtituted phenyl)-1,2,4-triazin-3-yl) piperazin- 1-yl]-2-[4-(3-substituted phenyl) piperazin-1-yl] ethanone derivative (1-32) compounds were synthesized by a four step synthetic procedure. The activity studies were evaluated using XTT method, BrdU method and flow cytometric analysis on MCF-7 breast cancer cells and NIH/3T3 (mouse embryonic fibroblast cells) healthy cells. Compounds 5 with 3-chlorophenyl and compound 7 with 4-chlorophenyl substitutions were found to be promising antiproliferative agents comparing with an effective anticancer drug, cisplatin

The selectively 15N labeled azido-1,2,4-triazine 2*A and azidopyrimidine 4*A were synthesized by treating hydrazinoazines with 15N-labeled nitrous acid. The synthesized compounds were studied by 1H, 13C, and 15N NMR spectroscopy in DMSO, TFA, and DMSO/TFA solutions, where the azide-tetrazole equilibrium could lead to the formation of two tetrazoles (T, T′) and one azide (A) isomer for each compound. The incorporation of the 15N label led to the appearance of long-range 1H-15N coupling constants (JHN), which can be measured easily by using amplitude-modulated 1D 1H spin-echo experiments with selective inversion of the 15N nuclei. The observed JHN patterns enable the unambiguous determination of the mode of fusion between the azole and azine rings in the two groups of tetrazole isomers (2*T′, 4*T′ and 2*T, 4*T), even for minor isoforms with a low concentration in solution. However, the azide isomers (2*A and 4*A) are characterized by the absence of detectable J HN coupling. The analysis of the JHN couplings in 15N-labeled compounds provides a simple and efficient method for direct NMR studies of the azide-tetrazole equilibrium in solution. © 2013 American Chemical Society.

An efficient method for the preparation of cycloalkene-anellated derivatives of monoazatriphenylenes based on an aza-Diels—Alder reaction of triazine (III) with 1-morpholinocycloalkenes is presented.

Intramolecular inverse electron demand cycloadditions of isatin-derived 1,2,4-triazines with acetylenic dienophiles tethered by amidations or transesterifications proceed in excellent yields to produce lactam- or lactone-fused α-carbolines. Beginning with various isatins and alkynyl dienophiles, a pilot-scale library of eighty-eight α-carbolines was prepared by using this robust methodology for biological evaluation.