3- Hydrazino-l,2,4-triazin-5 -one

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. 

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). 

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]

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-... 

Coupling of [2-(benzoyloxy)ethoxy]acetic acid (809) or [2-(l,3-diben-zoyloxy)propoxy]acetic acid 829 with 3-amino-6-hydrazino-l,2,4-triazin-5-one gave the two amides 827 and 830, respeetively. Thermal cyclodehydration of 827 and 830 and subsequent deprotection gave the two truncated-sugar acyclo C-nucleosides 828 (84JHC697) and 831 (95MI6) (Scheme 217). 

Equation (36)) <84JHC697>. Similarly, 3-Amino-6-hydrazino-l,2,4-triazin-5-ones (311) condense with carboxylic acids to give l,2,4-triazolo[3,4-/][l,2,4]triazin-8(7//) Ones (312) (Equation (37)) <84JHC697>. 

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). 

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). 

The reaction of 3-amino-6-bromo-l,2,4-triazin-5-one with hydrazines results in 6-hydrazino-substituted l,2,4-triazin-5-ones (Scheme 57). No indication for substitution at C-5 has been observed (75CCC2680). 

The IR spectra of Co(ll,lll) and Cu(ii) complexes of hydrazones obtained by the reaction of 5,6-diphenyl-3-hydrazino-l,2,4-triazine with furfural <2002TML398> and 2-acetylpyridine <2004JCR105> have been studied to determine the coordination sites of these ligands. In addition, Mn(ii), Ni(ii), and Cu(ll) complexes of hydrazones derived from 4-amino-3-mercapto-6-methyl-l,2,4-triazin-5(4//)-one were elucidated by IR spectra <2000SRI979>. 

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). 

Reaction of 6-amino-5-hydrazino-l,2,4-triazin-3-one (321) with orthocarboxylates affords the... 

Amino-5-hydrazino-[l, 2,4]-triazin-3(2H)-one (242) reacts with orthoesters and concentrated acid to give a mixture of ring-closed and open—chain derivatives which are converted in warm acid to the s-triazolotriazines (244) by a regiospecific ring-closure at N-4 of the [1,2,4]-triazine ring and subsequent Dimroth-type... 

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>. 

IIydrazino-5,6-diphenyl-l,2,4-triazine reacts with 4-arylidene-2-phenyloxazol-5(4//)-ones and 4-benzylidene-3-methylisoxazol-5(4//)-ones in toluene to afford products 19 and 20, respectively, substituted in the hydrazino group.299... 

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