Efficient routes to pyrazolo[3,4-e][1,2,4]triazines and a new ring system: [1,2,4]triazino[5,6-d][1,2,3]triazines

Abstract

Arylhydrazonomalononitriles 1a,b react with Phenylhydrazine to yield amidrazones 2a,b that cyclize to give 2-aryl-5-phenylhydrazono-2,5-dihydro-[1,2, 4]-triazine-6-carbonitriles 5a,b upon reaction with dimethylformamide dimethylacetal (DMFDMA). Refluxing 5a,b in glacial acetic acid resulted in the formation of the pyrazolo-1,2,4-triazines 6a,b. Compounds 6a,b were also formedupon treatment of 3-amino-4-phenylhydrazono-1-phenyl-2-pyrazolin-5-ones 7a,b with DMFDMA. Reacting these triazinyl arylhydrazononitriles 5a,b with hydroxylamine hydrochloride in ethanolic sodium acetate afforded amidrazones 8a,b that are readily cyclized in refluxing dimethylformamide into [1,2,4]triazino[1,2,3]triazines 10a,b. © 2010 by the authors.