Synthesis of 8-R-7-amino-3-tert-butylpyrazolo- [5,1-c][1,2,4]triazin-4(6H)-ones derivatives

Synthesis of a New Imidazo[4′,5′:3,4]pyrazolo[5,1‐c][1,2,4]triazine‐4,8‐dione Heterocyclic System

“…Ethyl 7‐amino‐3‐ tert ‐butyl‐4‐oxo‐4,6‐dihydropyrazolo[5,1‐ c ][1,2,4]triazine‐8‐carboxylate ( 2 ) was synthesized from 4‐amino‐6‐ tert ‐butyl‐3‐methylthio‐1,2,4‐triazin‐5(4 H )‐one and cyanoacetic ester via condensation reaction, and 7‐amino‐3‐ tert ‐butyl‐4‐oxo‐4,6‐dihydropyrazolo[5,1‐ c ][1,2,4]triazine‐8‐carbohydrazide ( 3 ) was prepared from compound 2 according to the procedures described earlier (Scheme ). In previous works, we demonstrated that the diazotization of compound 3 in various organic solvents resulted in formation of 3‐ tert ‐butyl‐4‐oxo‐4,6‐dihydropyrazolo[5,1‐ c ][1,2,4]triazine‐8‐carbonyl azide ( 4 ), which is formed by the transformation of carbonylhydrazide to carbonylazide and subsequent desamidization of the amino group attached to the C 7 .…”

“…Ethyl 7‐amino‐3‐ tert ‐butyl‐4‐oxo‐4,6‐dihydropyrazolo[5,1‐ c ][1,2,4]triazine‐8‐carboxylate ( 2 ) was prepared via condensation reaction of 4‐amino‐6‐ tert ‐butyl‐3‐methylthio‐1,2,4‐triazin‐5(4 H )‐one ( 1 ) with cyanoacetic ester in boiling pyridine . Synthesis of 7‐amino‐3‐ tert ‐butyl‐4‐oxo‐4,6‐dihydropyrazolo[5,1‐ c ][1,2,4]triazine‐8‐carbohydrazide ( 3 ) was performed by boiling amine 2 and aqueous hydrazine hydrate at reflux under argon atmosphere, and compound 7 was synthesized according to the procedure described in literature .…”

Interaction of Fused 1,2,4‐Triazinone with Diborane/Oxidation: A New Route for the Synthesis of Partially Saturated and Aromatic Pyrazolo[5,1‐c][1,2,4]triazines

“…Ethyl 3‐ tert ‐butyl‐4‐oxo‐4,6‐dihydropyrazolo[5,1‐ c ][1,2,4]triazine‐8‐carboxylate ( 2 ) was prepared from 4‐amino‐6‐ tert ‐butyl‐3‐methylthio‐1,2,4‐triazin‐5(4 H )‐one ( 1 ) in two steps according to the procedures described earlier . Ketone 4 was prepared as described in literature .…”

Interaction of 4‐Oxo‐4H‐pyrazolo[5,1‐c][1,2,4]triazin‐1‐ides with Grignard Reagents

“…4‐Amino‐3,7,8‐trinitropyrazolo[5,1‐ c ][1,2,4] triazine and its analogs have been considered as promising explosives . Thus, investigation of the reactivity of pyrazolo[5,1‐ c ][1,2,4]triazines remains an important task in the field of heterocyclic chemistry .…”

“…Aromatic core of this heterocyclic system showed high resistance towards concentrated acids and bases. For example, prolonged heating of ethyl 7‐amino‐3‐ tert ‐butyl‐4‐oxo‐4,6‐dihydropyrazolo[5,1‐ c ][1,2,4]triazine‐8‐carboxylate in a concentrated alcoholic KOH solution led to selective hydrolysis of the ester group . NH‐unsubstituted 4‐oxo‐4,6‐dihydropyrazolo[5,1‐ c ][1,2,4] triazines 1a are highly acidic and undergo deprotonation in the presence of bases ( 1b , Scheme ) .…”