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.     

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.     

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.     

The tert-butyl-NNO-azoxy group in the synthesis of 1,2,4-benzotriazin-3(4H)-one 1-oxides

Treatment of 2-(tert-butyl-NNO-azoxy)anilines with phosgene at 20 °C was proposed as a novel route to 1,2,4-benzotriazin-3(4H )-one 1-oxides. This method involves a new reaction, viz., an intramolecular interaction of the tert-butyl-NNO-azoxy group with a C-electrophile (leading to the formation of the N(2)—C(3) bond of the triazine ring) followed by elimination of the tert-butyl group. Complete assignment of the signals in the ¹H and ¹³C NMR spectra of the compounds obtained was performed. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1507–1509, August, 2007.     

Synthesis of 1-amino-1,2,4-triazolium 4-nitroimides and their reactions with electrophiles

A procedure was developed for the preparation of 1-amino-1,2,4-triazolium 4 nitroimides by amination of triethylammonium salts of 4-nitramino-1,2,4-triazoles with O-picrylhydroxylamine. The resulting nitroimides reacted with electrophilic reagents (acyl chlorides, aldehydes, phenyl isocyanate, NO₂BF₄, etc.) at the amino group.     

Synthesis and structures of 4,6-disubstituted 2-(5-methyl-1,2,4-oxadiazol-3-yl)-1,3,5-triazines

New 1,2,4-oxadiazolyl-1,3,5-triazines were synthesized from amidoximes derived from sym-triazine mononitriles. The structure of one of the resulting compounds was studied in detail by X-ray diffraction. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1845–1850, August, 2005.     

Reaction of 4-Amino-3-methylthio-5-oxo-6-R-4,5-dihydro-1,2,4-triazines with Sulfonylacetic Acid Nitriles

The reactions of 4-amino-3-methylthio-5-oxo-6-R-4,5-dihydro-1,2,4-triazines with arylsulfonylacetonitriles and with dinitriles of sulfonyldiacetic acid and methylenebis(sulfonylacetic) acid have been studied. 7-Amino-3-R-8-(R'-sulfonyl)-1,4-dihydropyrazolo[5,1-c][1,2,4]triazin-4-ones have been synthesized and these are the first representatives of geminal sulfones in which the heterocyclic ring is bound directly to the sulfur atoms of the sulfonyl groups.     

Tandem of nucleophilic substitution of hydrogen and cyclocondensation with participation of nitro group in the synthesis of fluorine-containing 3-amino-1,2,4-benzotriazines

Reactions of 3-fluoro-1-nitrobenzenes with guanidine hydrochloride in THF in the presence of Bu^tOK gave isomeric 5-and 7-fluoro-containing 3-amino-1,2,4-benzotriazines. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1196–1200, July, 2006.     

Synthesis of 2-amino-4-arylamino-6-benzo[<Emphasis Type="Italic">b</Emphasis>]furan-2-yl-1,3,5-triazines

The alkylation of salicylaldehyde and o-hydroxyacetophenone with 2-amino-4-arylamino-6-chloromethyl-1,3,5-triazines is accompanied by intramolecular condensation and affords 2-aryl-4-arylamino-6-benzo[b]furan-2-yl-1,3,5-triazines.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2758–2759, December, 2004.     

New 1,2,4-triazine-containing podands: synthesis and properties

A method of one-step C-C coupling of 1,5-bis(2,6-dimethylphenoxy)-3-oxapentane (1a) and 1,8-bis(2,6-dimethylphenoxy)-3,6-dioxaoctane (1b) with 3-methylthio- (2) and 3-amino-1,2,4-triazine (3) and 3-aryl-1,2,4-triazin-5-one (6-8) has been described. The reaction of compounds 1a,b with compounds 2 and 3 in the presence of trifluoroacetic acid results in the addition of the dimethylphenoxy group to the unsubstituted C(5) carbon atom of the triazine ring. The reactions of triazinones 6-8 with compounds 1a,b in a mixture of trifluoroacetic acid and organic anhydrides are accompanied by the acylation of the nitrogen atom adjacent to the reaction center and affords bis[(3-R-1-acyl-5-oxo-1,4,5,6-tetrahydro-1,2,4-triazin-6-yl)-2,6-dimethylphenoxy]-3-oxapentane or -3,6-dioxaoctane. The obtained adducts can smoothly be oxidized under mild conditions to form more stable products of nucleophilic hydrogen substitution in the triazine ring. The extraction and transport of Ca²⁺ and Mg²⁺ cations through an organic membrane by the compounds synthesized are discussed.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2210–2215, October, 2004.     

Condensed Thienopyrimidines. 14. Synthesis of 10H-Thiopyrano[4',3':4',5']thieno[2',3':4,5]pyrimido[2,3-c]-1,2,4-triazines

Reaction of a substituted 2-aminothienothiopyran with methyl(phenyl) isothiocyanate, intramolecular cyclization of the obtained N'-methyl(phenyl) thioureido derivatives, and work up of the cyclization products with hydrazine hydrate gave 2-hydrazinodihydrothiopyranothienopyrimidines. Treatment of the latter with pyruvic acid gave the novel 10H-thiopyrano[4',3':4',5']thieno[2',3':4,5]pyrimido[2,3-c]-1,2,4-triazines.     

CuCl2 induced reactions of 6-ethynyl- and 6-cyano-5-aryl-2,2′-bipyridines with various N- and O-nucleophiles in comparison with the reactions of relative 1,2,4-triazines

Meanwhile 5-aryl-6-cyano-2,2′-bipyridines are very stable towards various nucleophiles, addition copper(II) chloride to the reactional mixture facilitates nucleophilic addition to the cyano group dramatically. The cyanobipyridines react easily with water, methanol, ethanolamine in the presence of CuCl₂ yielding well-crystallized complexes containing carboxylates, carboximidates or carboxamidines as ligands. 5-Cyano-1,2,4-triazines are more active in the reactions due to higher electron-withdrawing properties of this heterocycle. Due to the same reason acetylene moiety of 5-ethynyl-3-pyridyl-1,2,4-triazine adds water quite easily but in the presence of copper chloride as well.     

SNH reactions of 1,2,4-triazine N-oxides,pyrazine N-oxides,and pterin N-oxides with arenethiols*

1,2,4-Triazine 4-oxides were found to enter into the reactions of nucleophilic substitution of hydrogen with S-nucleophiles (arenethiols) in the presence of acylating agents and trifluoroacetic acid. The reactions proceeded with loss of the N-oxide function to form 5-arylthio-1,2,4-triazines. 2-Amino-3-ethoxycarbonylpyrazine 1-oxides and 2-amino-4-oxopterin 8-oxides react with arenethiol analogously.     

SNH-Reactions of triazolo[4,3-b]- and tetrazolo[1,5-b]-1,2,4-triazines with methylene-active carbonyl compounds

Unsubstituted triazolo[4,3-b]- and tetrazolo[1,5-b]-1,2,4-triazines react with carbanions generated from dimedone and barbituric acid to give adducts of a C-nucleophile with the heterocyclic system through the C=N double bond. The adducts can be oxidized under mild conditions into products of nucleophilic hydrogen substitution. Analogous adducts with carbanions produced in the reactions of ethyl cyanoacetate and ethyl malonate with Bu^tOK proved to be unstable; in this case, the title azolotriazines immediately yield products of nucleophilic hydrogen substitution in position 7. Tautomerism of the S _N ^H products obtained is discussed.     

Easy formation of SNH products in reactions of indoles and pyrroles with 3-aryl-1,2,4-triazin-5(2H)-ones in the presence of tosyl chloride

The reactions of 3-aryl-1,2,4-triazin-5(2H)-ones with indoles and pyrroles in the presence of p-toluenesulfonyl chloride afforded 3-aryl-6-hetaryl-1,2,4-triazin-5(2H)-ones in high yields. The latter are products of the nucleophilic substitution of hydrogen.     

Synthesis of 4<Emphasis Type="Italic">H</Emphasis>-imidazole-5-carbaldoxime 3-oxides and 4<Emphasis Type="Italic">H</Emphasis>-imidazole-5-carbonitrile 3-oxides

The condensation of 3-hydroxyamino-3-methylbutan-2-one or 3-ethyl-3-hydroxyamino-pentan-2-one with aldehydes and ammonia afforded a series of new 1-hydroxy-4-methyl-2,5-dihydroimidazoles, whose oxidation gave rise to the corresponding 5-methyl-4H-imidazole 3-oxides. The latter, like 1-hydroxy-4-methyl-2,5-dihydroimidazoles, react with PrⁱONO in the presence of bases to form 4H-imidazole-5-carbaldoxime 3-oxides, which are transformed into 4H-imidazole-5-carbonitrile 3-oxides in the reaction with TsCl in the presence of Et₃N. The by-products produced in different steps of the synthesis were isolated and characterized. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1487–1503, July, 2008.     

Reactions with heterocyclic amidines,VII: Synthesis of some new pyrazolo[1,5-c]-1,2,4-triazines,pyrazolo[1,5-a]-1,3,5-triazines and pyrazolo[1,5-a]pyrimidines

Diazotised 5-amino-3-methyl-4-phenyloyrazole (1) reacted with active methylene reagents and with -naphthol to yield the pyrazolo[1,5-c)-1,2,4-triazine derivatives2a-e and5. Compound1 reacted with benzoyl isothiocyanate and with phenyl isothiocyanate to yield the corresponding pyrazol-5-ylthiourea derivatives6a, b. 5a was converted into the thiourea derivative8 by the action of acids or alkalies. A synthesis of 2-methyl-3-phenyl-4,5,6,7-tetrahydropyrazolo[1,5-a]-pyrimidin-5-one from the reaction of -phenylacetoactonitrile (3-oxo-2-phenyl-butyric nitrile) and -cyanoethylhydrazine is reported.

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Reaktionen mit heterocyclischen Amidinen, VII: Synthese einiger neuer Pyrazolo[1,5-c]-1,2,4-triazine, Pyrazolo[1,5-a]-1,3,5-triazine und Pyrazolo[1,5-a]pyrimidine

Zusammenfassung Diazotiertes 5-Amino-3-methyl-4-phenylpyrazol (1) reagiert mit einer aktiven Methylenkomponente und -Naphthol zu den Pyrazolo[1,5-c]-1,2,4-triazin-Derivaten2a-e und5. 1 ergibt mit Benzoylisothiocyanat und Phenylisothiocyanat die entsprechenden Pyrazol-5-yl-thioharnstoffe6a, b. 5a wurde mittels Säure oder Base in das Thioharnstoffderivat8 umgewandelt. Es wird über eine Synthese von 2-Methyl-3-phenyl-4,5,6,7-tetrahydropyrazolo[1,5-a]-pyrimidin-5-on aus -Phenylacetoacetonitril (3-Oxo-2-phenyl-butyronitril) und -Cyanoethylhydrazin berichtet.

     

Microwave-induced generation and reactions of nitrile sulfides: an improved method for the synthesis of isothiazoles and 1,2,4-thiadiazoles

The 1,3-dipolar cycloaddition reactions of nitrile sulfides, generated by microwave-assisted decarboxylation of 1,3,4-oxathiazol-2-ones, have been investigated. By this approach ethyl 1,2,4-thiadiazole-5-carboxylates 3 were prepared in good yield by cycloaddition of the nitrile sulfides to ethyl cyanoformate. Similarly, reaction of benzonitrile sulfide with dimethyl acetylenedicarboxylate (DMAD) afforded dimethyl 3-phenylisothiazole-4,5-dicarboxylate (5). In contrast, o-hydroxybenzonitrile sulfide, generated from the corresponding oxathiazolone 2d, reacted with DMAD to give methyl 4-oxo-4H-[1]benzopyrano[4,3-c]isothiazole-3-carboxylate (8) in high yield. A ca. 1:1 mixture of ethyl 3-phenylisothiazole-4- and 5-carboxylates (6,7) was formed from benzonitrile sulfide and ethyl propiolate. The corresponding reaction with diethyl fumarate gave diethyl trans-4,5-dihydro-3-phenylisothiazole-4,5-dicarboylate (10). 3-Arylisothiazoles, unsubstituted at both the 4- and 5-positions, were prepared from the reaction of 5-aryl-1,3,4-oxathiazolones with norbornadiene by a pathway involving cycloaddition of the nitrile sulfide to the norbornadiene, followed by retro-Diels-Alder extrusion of cyclopentadiene from the resulting isothiazoline cycloadduct 12. In summary, the use of microwave irradiation, rather than conventional heating methods, allows nitrile sulfide generation and reactions to be carried out in shorter times, with easier work-up and, in some cases, in higher yields.     

新型3-取代-6-(4-氯苯基)-7-(1H-1,2,4-三唑-1-基)-1',2',4'-三唑[3,4-b]-1",3",4"-噻二嗪衍生物的合成及抗菌活性

通过3-取代-4-氨基-5-巯基-1,2,4-三唑(3a～3m)和2-溴-2-(1H–1,2,4-三唑-1-基)-4′-氯代苯乙酮(2)的缩合反应, 合成了13个新型3-取代-6-(4-氯苯基)-7-(1H-1,2,4-三唑-1-基)-1',2',4'-三唑[3,4-b]-1",3",4"-噻二嗪衍生物4a～4m. 化合物结构经元素分析, ¹H NMR, IR和MS进行了表征. 抗菌试验表明所合成的化合物对细菌表现出中等程度的抑制活性.