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. 2010 May 4;15(5):3302-10.
doi: 10.3390/molecules15053302.

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

Hamad Mohamed Al-Matar  1 , Khaled Dessouky Khalil, Doa'a Mohamed Al-Dorri, Mohamed Helmy Elnagdi
Affiliations

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

Hamad Mohamed Al-Matar et al. Molecules. .

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 formed upon 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.

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Figures

Scheme 1
Scheme 1
Proposed mechanism for the formation of 2-aryl-6-phenyl-2H-pyrazolo[3,4-e][1,2,4]triazin-7(6H)-ones 6a,b.
Scheme 2
Scheme 2
Proposed mechanism for the formation of 6-aryl-2-phenyl-2,6-dihydro-[1,2,4]triazino[5,6-d][1,2,3]triazin-4-amines 10a,b.
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