7.8- Diamino-1,2,4-triazolo pyrimidine

Treatment of 5,7-diamino-l,3,4-thiadiazolo[3,2-n]pyrimidinium ehloride (25) with Vilsmeier reagent gave the 7-formamido-l,2,4-triazolo[l,5-c]pyrimidin-5-one (27) (90JHC851) (Seheme 42). Compound 27 has presumably been formed via rupture of the 1,3,4-thiadiazole ring of 25 and... 

Fluorophenylacetyl and 4-fluorophenylacetyl chlorides selectively ac-ylated the C8-NH2 group of 7,8-diamino-l,2,4-triazolo[l,5-c]pyrimidine 139 (94JHC1171) to give 140 (Scheme 54) N6 of the ring system probably renders the closer C7-NH2 group less nucleophilic than the remoter C8-NH2 function. 

The reactions of 5-methylthio-3-amino- or 3,5-diamino-l,2,4-triazole and diethyl 1-ethoxyethylidenemalonate in boiling ethanol in the presence of sodium ethylate for 1.5-3.5 hr gave l,2,4-triazolo[l,5-a]pyrimidin-7-ones (1123, R = MeS, NH2, R1 = Me) in 44% and 20% yields, respectively. The reaction of 5-methylthio-3-amino-l, 2,4-triazole (R = MeS) and 2-ethoxyethylidenemalonate in boiling pyridine for 4 hr gave 1,2,4-tria-zolo[l,5-a]pyrimidin-5-one (1122, R = MeS, R1 = Me) in 12% yield (61JCS3046). 

Diamino-5-oxo-l,2,4-triazolo[l,5-a]pyrimidine together with nitrous acid affords a fused triazolo-TP. 

Chloro-3-formyl-4-oxo-4/Y-pyrido[l,2-a]pyrimidine was transformed with hydrazine and ethylenediamine, respectively, to the tricyclic compounds 22898 and 229.285 Treatment of 2,3-diamino-4-oxo-4//-pyrido[l,2-a]pyrim-idines with sodium nitrite in aqueous acetic acid afforded the pyrido [1,2-a]-r-triazolo[4,5-d]pyrimidines (230).31 Reaction of the pyrido[l,2-a]pyrimi-... 

Aryl-7,8-diamino-1,2,4-triazololl, 5-c]pyrimidines (97 R= H) selectively acylate on the 8-amino group to give the amides (97 R= R CO) which cyclise on heating with PPA to yield 2-aryl-8-fIuorobenzyl-l,2,4-triazolo[5,l-/]purines (98) [94JHC1171],... 

Diazotization of a mixture of diamino derivatives (R,S)-22 afforded the triazolo[l,5-c]pyrimidine 23. When the reaction time and the proportion of sodium nitrite were increased, a second compound 24, resulting from a reductive deamination of the amino group [89JCS(P1)2401] was obtained (Scheme 5). 

The l,2-diamino-4-methylthiazole 73 with phosgeniminium chloride gives the thiazolo[3,2-A [l,2,4]triazole derivative 74 (Scheme 45) <1973AGE806>. Reaction of the sulfimide 75 with nitrile oxides forms [l,2,4]triazolo[l,5- ] pyridine 3-oxides 76 in good yields (Scheme 46). This method is applicable to analogous pyrimidines and pyrazines <1976J(P1)2166, 1978BCJ563>. 

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