3-Hydrazino triazin-5-one

Further work by Adembri et al. describes the irradiation of 5-hydrazino-isoxazoles 291a-b under nitrogen, which gives a mixture of products analogous to that obtained by thermal isomerization 5-methylaminopyrazol-3-ones 292a-b, 4-aminopyrazol-3-ones 293a-b, and l,2,4-triazin-6-ones 294 -b (78TL4439). 

Hydrazino-3-methylbutan-2-one oxime reacts with aldehydes and ketones, resulting in l,3,4,6-tetrahydro-l,2,4-triazine 4-oxides 155 (77ZOR2617). 

This ring system is represented by tricyclic ring system 533 (76JHC1249). Reaction of 3-hydrazino[l,2,4]triazin-5-ones 531 with 3-imi-nobutyronitrile afforded 6-methyl- (or phenyl-) 3-[3-methyl-5-aminopyra-zolyl]-2,5-dihydro[l,2,4]triazin-5-ones 532A, which may exist in tautomeric form 532B. Its reaction with diethoxymethyl acetate (DEMA) or ortho-esters afforded the tricyclic compounds 533. 

Dicyanomethyl)-6-methyl-l,2,4-triazin-5-one (45a) is formulated as the methylene tautomer (45b) (67CB2585). 2-Anilino-2-hydrazino-l-nitroethylene (46) reacts with biacetyl to give a compound which is formulated as the dimethylene structure (47) (77JPR149). 

Azido-2H-l,2,4-triazin-3-ones (56a) also cyclize to give the tetrazolo[5,l-d]-[l,2,4]triazin-3-ones (56b) (71RRC135, 71RRC311). Nitrosation of 3-amino-6-hydrazino-l,2,4-triazin-5-one (57) affords a compound which exhibits an intense absorption at 2140cm-1, showing that the 6-azido tautomer (58a) was isolated. When this compound was stirred for a few minutes in a polar solvent it quantitatively formed the tetrazole tautomer (58b) (79JHC555). 

Reaction of 4-aryl-3-methylthio-l,2,4-triazin-5-ones (342) with hydrazine led to 4-amino-3-arylamino-l,2,4-triazin-5-ones (343) instead of the expected 4-aryl-3-hydrazino derivatives (344). This is explained by nucleophilic attack of the hydrazine at the 5-position, ring opening and subsequent reclosure. The same result was obtained when 4-aryl-3-thioxo-... 

HC(33)189, p.475) and 3-hydrazino-l,2,4-triazin-5-ones (484) (78HC(33)189, p.494), respectively. It is not necessary to isolate the initially formed hydrazones, but these can be cyclized by heatihg in DMF (Scheme 16). 

One of the classical methods for the generation of imidoyl azides as precursors to mono- and disubstituted tetrazoles is based on reactions of amidrazoles with sodium nitrite. This procedure developed by Kaufmann et al. in the middle of thel960s <2004SOS(13)861> has found an extension and advancement in recent studies. By this method, 5-hydrazino-3-methyl-l-phenyl-l//-pyrazolo[4,3-< ][l,2,4]triazine 503 through a cyclic imidoyl azide 504 was converted into 5-phcnyl-l //-pyra/olo[4,3-<,]tetrazolo[4,5- tria/inc 505 (Scheme 64) <2005JCX151>. 

Reactions of 3-hydrazino-l,2,4-triazin-5-one derivatives with carbonyl compounds to give triazolotriazine derivatives have been reported <03KGS1376>. Intramolecular inverse electron demand cycloadditions of 2-substituted imidazoles with various 1,2,4-triazines produced both imidazo[4,5-c]pyridines (3-deazapurines) and pyrido[3,2-[Pg.387]

Reaction of 3-amino-6-hydrazino-l,2,4-triazin-5(2/f)-one (368) with nitrous acid has produced (369) as a representative of this class of compounds (79JHC555). 

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