5-oxo-l,2,4-triazine

The presence of a 5-oxo group in the 1,2,4-triazines, as in 3-hydrazino-2,5-dihydro-5-oxo[l,2,4]triazines, does not alter the direction of cycliza-tion by the action of nitrous acid. The initial products are azido compounds 1016, which can cyclize spontaneously to tetrazolo[l,5-b][l,2,4]triazines 1017 (77JHC1221, 77JOC1866) rather than the previously reported isomeric structure. On the other hand, when the cyclization onto N-2 is impossible, as in derivative 1018, the azidotetrazolo equilibrium 1018 1019 exists (76JOC2860 77JOC1866). It exists in the solid state at least as the tetrazole derivative (Scheme 190). 

C7H22N2 140-80-7) see Chloroquinc Mepacnne 7(77)-amino-3-[[(2,5-dihydro-6-hydroxy-2-methyl-5-oxo-l,2,4-triazin-3-yl)thio]mcthyl]-3-cephem-4-carboxylicadd (C12H13N5O5S2 58909-56-1) see Ceftriaxone (15-franx)-l-amino-2,3-dihydro-l//-inden-2-ol (CyH NO 163061-74-3) see Indinavir sulfiite cis-l-amino-2,3-dihydro-l//-inden-2-ol (C9H11NO 7480-35-5) see Indinavir sulfate... 

Alkylation of l,2,4-triazine-3,5-dione (33 R = H) with dimethyl sulfate at 135-145 °C without a base afforded l-methyl-5-oxo-l,2,4-triazin-3-olate (185), the structure of which was proved by hydrogenation to be the dihydro compound (186) (73CCC934). 

The reactions of CpTiCl3 with 4-amino-3-mercapto-6-methyl-5-oxo-l,2,4-triazine and its Schiff bases (derived from benzaldehyde, 2-chlorobenzaldehyde, anisaldehyde, salicylaldehyde, 2-hydroxynaphthaldehyde, and 2-hydroxyace-tophenone) have been studied in THF and CH2G12 in the absence and presence of amine in different molar ratios.997... 

The 5-carboxymethyl-1,2,4-triazole and 5-oxo-l,2,4-triazine derivatives have been examined by C CPMAS NMR. ... 

The infrared (IR) absorption spectra of a number of azauracils, such as 5-oxo-l,2,4-triazin-3-thione, 3-oxo-l,2,4-triazin-5-thione, and l,2,4-triazin-3,5-dithione, isolated in low-temperature nitrogen matrices have been reported. These compounds exist in low-temperature matrices exclusively in the oxothione and dithione tautomeric forms. Assignments of the observed IR bands were made on the basis of comparison of the experimental spectra with those obtained by ab initio SCF/6-311G calculations <1996SAA645>. Additionally, IR spectroscopy has been used to study the photoisomerization reaction of 6-methyl-5-oxo-l,2,4-triazin-3-thione <2005PCA7700>. The IR spectra revealed that before UV irradiation the matrix-isolated compound adopts exclusively the oxo-thione tautomeric form. 

In continuing their previous work Bougault and Daniel observed that thiosemicarbazones of a-keto acids (51) also undergo a cyclization resulting in 3-thioxo-5-oxo-2,3,4,5-tetrahydro-l,2,4-triazines (52). In contrast with the cyclization of semicarbazones this cyclization... 

Thioxo-3-oxo-2,3,4,5-tetrahydro-l,2,4-triazine (4-thio-6-azauracil) (88) and 3,5-dithioxo-2,3,4,5-tetrahydro-l,2,4-triazine (2,4-dithio-6-azauracil) (89) w ere prepared by Hitchings et al. treating 6-aza-... 

In agreement with the results of Cattelain, further methylation of the 3-methylmercapto derivative (96) results practically exclusively in 2-methyl-3-methylmercapto-5-oxo-2,5-dihydro-l,2,4-triazine (97). Further methylation of 5-methylmercapto derivative (90) yields 2-methyl-5-methylmercapto-3-oxo-2,3-dihydro-l,2,4-triazine (100). Their structure was confirmed by acid hydrolysis leading to 2-methyl-3,5-dioxo derivatives (62), As was already mentioned, this reaction is a suitable general procedure for preparing the 1-alkyl derivatives of 6-azauracil. ... 

The course of methylation of all the thio derivatives with diazomethane was then investigated. These mcthylations generally result in mixtures of substances it may be deduced from the products isolated, however, that this reaction proceeds first at the nitrogen atom (in contrast with alkaline methylation) and only then at the sulfur one. The methylation of the 3-methylmercapto derivative to 4-methyl-3-methylmercapto-5-oxo-4,5-dihydro-l,2,4-triazine (95) is of interest in this connection. 

Oxo 5-imino-2,S,J, 5-tetrahydro-l,, 4-triazine 6-Azacytosine) Substances of this type were not studied by the earlier workers, and the first representative of this group to be investigated was 3-oxo-5-imino-2,3,4,5-tetrahydro-l,2,4-triazine (122) which should bear the name 6-azacytosine. It was prepared by Falco et al. by treating 3-thioxo-5-oxo-2,3,4,5-tetrahydro-l,2,4-triazine (88) with alcoholic ammonia. Some iV-substituted derivatived were prepared anal-ogously. ... 

Derivatives of 3-oxo-l,2,4-triazine 1-oxide undergo alkylation with various alkylating agents. Thus the reaction of 3-methoxy-l,2,4-triazine 1-oxide 20 with 2,3,5-tii-(9-benzoyl-/3-D-ribofuranosyl bromide, followed by the removal of the benzoyl protection with sodium methoxide, leads to an abnormal nucleoside 4-(/3-D-iibofuranosyl)-l,2,4-triazin-3(4//)-one 1-oxide 21 (73JOC3277). 

Die 3-Oxo-2,3,4,5-tetrahydro-l,2,4-triazine werden dagegen im sauren Medium unter Ammoniak-Abspaltung zu 2-Hydroxy-imidazoI reduziert2 ... 

Most of the reported triazinothiadiazines have been prepared from 1,2,4-triazine derivatives. Treatment of amino-1,2,4-triazine 28 with chloroacetyl chloride in dioxane in the presence of triethylamine at 10 °C resulted in the formation of 6-methyl-4-(A -chloroacetamido)-3-thioxo-5-oxo-2,3,4,5-tetrahydro-l,2,4-triazine 29 and 3-methyl-4,7-dioxo-4,6,7,8-tetrahydro-l,2,4-triazino[3,4-A][l,3,4]thiadiazine 15 (Scheme 1) <2005JHC935>. 

There is considerable interest in the chemistry of triazines as some of these compounds show pronounced antimalarial, antimicrobial and antiviral activity (76JCS(Pl)252l). Therefore two types of thiophenes annelated with a triazine ring will be mentioned. Thieno[2,3-d]-1,2,3-triazines were synthesized by cyclization of diazotized 2-aminothiophene-3-carboxamides (equation 55) (73M1586). Treatment of 3-alkylthio-6-styryl-5-oxo-2,5-dihydro-l,2,4-triazines with phosphorus pentasulfide in pyridine yields thieno[2,3-e]-l,2,4-triazines (equation 56) (78CI(L)585). Probably a thiation with subsequent cycloaddition and elimination of a hydride ion is involved. 

On the other hand, a proton directly bound to the 1,2,4-triazine ring can be replaced by halogen. This is an electrophilic substitution reaction at carbon, and, as expected for such a heavily aza-substituted ring system, it needs considerable activation by electron-donating substituents. The halogenation reaction is best known in bromination at the 6-position. From the published data it seems that either an amino group in the 3-position or an oxo group in the 5-position is necessary. The formation of 6-halo-substituted compounds has been reported for l,2,4-triazin-5-ones, l,2,4-triazine-3,5-diones, 3-amino-l,2,4-triazines and 3-amino-l,2,4-triazin-5-ones. 

Alkylation reactions were recently performed with all the thio derivatives of 6-azauracil and 6-azathymine. In agreement with previous findings, the methylmercapto derivatives were obtained by alkylation of all these substances in alkaline solution. Thus, e.g., 3-ihethylmercapto-6-oxo-2,5-dihydro-l,2,4-triazine (96), 5-methylmer-capto-3-oxo-2,3-dihydro-l,2,4-triazine (90), and 3,5-dimethylmer-capto-l,2,4-triazme (91) were obtained. The last-named of these was... 

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