Synthesis of 3-aminobenzo-1,2,4-triazine 4-oxides

o-Quinone monooxime guanylhydrazones, obtained from copper complexes of o-nitrosophenols, are cyclized to give the previously unknown 3-aminobenzo-1,2,4-triazine 4-oxides.     

From 3-chloromethyl-1,2,4-triazine 4-oxides to various substituted pyridines and 1,2,4-triazines

An efficient strategy for the synthesis of new pyridine and 1,2,4-triazine derivatives starting from available 6-aryl-3-chloromethyl-1,2,4-triazine 4-oxides was proposed. The deoxygenative nucleophilic hydrogen substitution in the triazine-oxide ring, nucleophilic substitution of the chlorine atom in the side chain, and transformations of the 1,2,4-triazine ring into the pyridine ring via the inverse-electron-demand Diels-Alder reactions, being used in different orders, are a rather flexible tool for the functionalization of the titled heterocycles. The cyanide anion, indoles, thiophenols, amines, and triphenylphosphine were used as nucleophiles. The direct introduction of indole residues into the 1,2,4-triazine ring followed by the substitution of the chlorine atom by a residue of the primary or secondary aliphatic amine was found to be the most convenient method for the library synthesis. Dedicated to Academician N. S. Zefirov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2122–2131, September, 2005.     

Lithiacarboranes and 1,2,4-triazine 4-oxides: S N H reactions and ring transformations

The reactions of 1-lithia-1,2- or 1,7-dicarba-closo-dodecaborane with 1,2,4-triazine 4-oxides can follow two competitive pathways: deoxygenative nucleophilic substitution of hydrogen to form 1-(1,2,4-triazin-5-yl)-1,2- or 1,7-dicarba-closo-dodecaboranes and the transformation of the 1,2,4-triazine ring into the triazoline ring giving rise to 1-(2-acetyl-1-aroyl-3-aryl-1,2,4-triazolin-5-yl)-1,2-dicarba-closo-dodecaboranes. Introduction of the electron-withdrawing triazine ring into the carborane cage substantially facilitates deboronation to give 1-(1,2,4-triazin-5-yl)-1,2-1,7-dicarba-nido-undecaboranes.     

Effect of substituent in pyridine-2-carbaldehydes on their heterocyclization to 1,2,4-triazines and 1,2,4-triazine 4-oxides

A series of substituted pyridine-2-carbaldehydes were brought into heterocyclization with isonitrosoacetophenone hydrazones, followed by aromatization by the action of oxidants or by dehydration in boiling acetic acid. As a result, substituted 3-(pyridin-2-yl)-1,2,4-triazines or 3-(pyridin-2-yl)-1,2,4-triazine 4-oxides were formed. 6-Formylpyridine-2-carbonitrile failed to undergo heterocyclization, 6-methylpyridine-2-carbaldehyde and methyl 6-formylpyridine-3-carboxylate can be converted to both 1,2,4-triazine and 1,2,4-triazine 4-oxide derivative, and only 1,2,4-triazine 4 oxides were obtained from 6-bromopyridine-2-carbaldehyde and 6-formyl-3-phenylpyridine-2-carbonitrile. Convenient procedures were proposed for the synthesis of some initial pyridinecarbaldehydes.     

S N H reactions of pyrazine N-oxides and 1,2,4-triazine 4-oxides with CH-active compounds

Nucleophilic substitution of hydrogen in pyrazine N-oxides under the action of CH-active compounds requires activation with acylating agents. This activation facilitates aromatization of intermediate ^H adducts via elimination of the acid residue to form substituted pyrazines. More electrophilic 1,2,4-triazine 4-oxides react with carbanions derived from CH-active compounds without additional activation according to a scheme, which has previously been unknown for azine N-oxides. This scheme involves aromatization of ^H adducts through elimination of water by the E1cb mechanism. The reaction products occur in DMSO-d₆ solutions predominantly as 6-methylene-1,6-dihydropyrazines and 5-methylene-4,5-dihydro-1,2,4-triazines.     

Mass spectra of some 1,2,4-triazine 1- and 2-oxides

A study of the fragmentation patterns of a variety of substituted 1,2,4-triazine 1- and 2-oxides has been undertaken. It is shown that the fragmentation patterns of the 1- and 2-oxides are extremely similar with the relative peak intensities varying with the type of substituents present.     

Nucleophile-induced transformations of 1,2,4-triazines. 3. Anrorc constriction of the ring in the reaction of 6-aryl-3-dimethylamino-1,2,4-triazine 4-oxides with KCN

Reaction of 6-aryl-3-dimethylamino-1,2,4-triazine 4-oxides with KCN results in constriction of the heterocycle and formation of 3-amino-5-aryl-4-nitrosopyrazoles. Several methods including labelled K¹³C¹⁵N are used to demonstrate that the reaction proceeds through the ANRORC mechanism. Dedicated to Professor Henk van der Plas on his 70th birthday. For No. 2, see [1]. Urals State Technical University, Ekaterinburg 620002, Russia; e-mail: mike@htf.ustu.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 532–535, April, 1999.     

Rearrangement of 4-aryl-1,2,4-triazine into the 4-amino derivatives

The action of hydrazine on 3-methylmercapto-5-oxo-4-aryl-4,5-dihydro-1,2,4-triazines led to a novel rearrangement and gave 3-arylamino-4-amino-5-oxo-4,5-dihydro-1,2,4-triazines. The mechanism of this rearrangement was discussed.     

Reactions of 4-nitroso-1,2,4-triazine with derivatives of hydrazine

The action of hydrazine on 4-nitroso-6-phenyl-1,2,4-triazine-3(2H)-thione-5-one results in the cleavage of the nitroso group. The action of phenylhydrazine results in the reduction of the double bond in the triazine ring together with the cleavage of the nitroso group. The spectral characteristics of the compounds are considered, and the reaction mechanism is proposed.Sumy State University, Sumy, 244007. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1421–1423, October, 1996. Original article submitted May 20, 1996.     

Anti-oxidative properties of bi-1,2,4-triazine bisulphides

The anti-oxidative properties of bitriazines (BTs) were evaluated using HPLC and cyclic voltammetry. In the first case, a RP-HPLC assay was made, using a fluorescence detector, hydroxyl radicals generated in Fenton reaction, and terephthalic acid as a spin trap. The measurements were performed using aqueous or methanolic solutions. It was found that when the BTs were dissolved in water they were antioxidants, while dissolved in methanol they were pro-oxidants. Their different physicochemical properties in both solvents were confirmed by voltammetric, chromatographic as well as spectrophotometric measurements.     

Nucleophilic substitution of hydrogen in the reaction of 1,2,4-triazin-4-oxides with cyanamide

It was shown that cyanamide can successfully be used in reactions of nucleophilic substitution of hydrogen with 1,2,4-triazin-4-oxides in the presence of a base to give 5-cyanoimino-1,2,4-triazines. It was found by¹³C NMR spectroscopy that these compounds and their alkylation products at the cyclic nitrogen atom exist in the form of 5-cyanoimino-2,5-dihydro-1,2,4-triazines. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1128–1130, June, 2000.     

Condensed imidazo-1,2,4-azines. 4. Synthesis of 1,4-Dihydroimidazo[1,5-c]-1,2,4-triazine derivatives

The reaction of 2-methyl-4(5)-nitro- and 2-methyl-4(5)-nitro-5(4)-bromoimidazoles with -halo ketones was investigated, during which a number of 1-acylmethyl-substituted 2-methyl-4-nitro- and 2-methyl-4-nitro-5-bromoimidazoles were obtained. 1,4-Dihydro derivatives of imidazo[1,5-c]-1,2,4-triazine were synthesized by reaction of the latter with hydrazine and its monosubstituted derivatives. The structures of the 1-acylmethyl-substituted 2-methyl-4-nitro-5-bromoimidazoles and 1,4-dihydro derivatives of imidazo[1,5-c]-1,2,4-triazine were confirmed by their IR, PMR, and mass spectra.See [1–3] for Communications 1–3, respectively.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 833–837, June, 1981.