Synthesis of condensed mesoionic heterocycles. Intramolecular cyclization of 3-acetonyl(phenacyl)-1,2,3-triazolium-5-olates

Syntheses and Applications of 1,2,3-Triazole-Fused Pyrazines and Pyridazines

“…Methods have been reported for the preparation of 1,2,3-triazolo[1,5- a ]pyrazinones. In work by Nein and coworkers [ 37 , 38 ], the reaction of 5-hydroxy- N -diphenyl-1 H -1,2,3-triazole-4-carboxamide 41 with chloroacetonitrile in DMF and base gave the alkylated product 42 , which, after refluxing in sodium ethoxide, gave 6-amino-4-oxo-2,5-diphenyl-4,5-dihydro-2 H -1,2,3-triazolo[1,5- a ]pyrazinium-5-olate 43 in 80% yield ( Scheme 9 ). They proposed the geometry of 3-phenacyl- and 3-cyanomethyl derivatives of triazolium-5-olates indicated interaction of the carboxamide nitrogen at position 4 of the triazole with cyano groups, which was then confirmed experimentally after obtaining the desired mesoionic 42 [ 37 ].…”

Synthesis of [1,2,3]Triazolo[1,5-a]Pyrazinium-3-Olates*

“…Some condensed mesoionic 1,2,3-triazolium-5-olates have been shown to act as immunosuppressants [9]. Previously we have shown [10][11][12] that alkylation of 1-aryl-and 1-arylmethyleneamino-1,2,3-triazol-5-olate sodium salts with alkyl halides leads to the zwitterionic 3-alkyl-1,2,3-triazol-3-ium-5-olate and [1,2,3]triazolo[1,5-а]pyrazinium-3-olate. In a continuation of our research in the field of mesoionic heterocycles [13][14][15][16], in this work we present the synthesis of new [1,2,3]triazolo[1,5-a]pyrazinium-3-olate derivatives.…”

“…The geometry of 3-phenacyl-and 3-cyanomethyl derivatives of triazolium-5-olates 1а-с [10][11][12] indicates a possible interaction of carboxamide group nitrogen atom at position 4 of the triazole ring with keto or cyano groups, forming a condensed zwitterionic triazolopyrazine. Indeed, refluxing of 3-cyanomethyl derivatives 1a-c with sodium ethoxide for 5 h resulted in good yields (up to 80%) of the individual bicyclic compounds 2a-c.…”