Abstract
The monoacyl derivatives from 6-methyl-3-phenyl-1H-pyrazolo(5,1-c)(1,2,4)-triazole 1 may exist in three isomeric forms. Spectroscopic and chemical arguments are presented for the confirmation of the identities of the resulting products.
Highlights
Interest in 6-alkyl-3-aryl(alkyl)-1H-pyrazolo[5,1-c][1,2,4] triazoles 1 is commonly attributed to their use as precursors for color photosensitive materials1-3, their role in inks and toners, as ingredients in cosmetics and for their biological activity4-7
Because the pyrazolo[5,1-c][1,2,4]triazole system can exist as three tautomeric forms, 1a, 1b, 1c, monoacylation can produce three isomers: the keto form, 7-acyl-6-methyl-3-phenyl-1Hpyrazolo[5,1-c][1,2,4]triazole 2c, and two hydrazides, 1-acyl-6-methyl-3-phenyl-7Hpyrazolo[5,1-c][1,2,4]triazole 2a and 5-acyl-6-methyl-3-phenyl-7H-pyrazolo[5,1-c] [1,2,4]triazole 2b
All the acetylation reactions of 6-methyl-3-phenyl-1H-pyrazolo[5,1-c][1,2,4]triazole 1a led to the same N-monoacetylated compound, as the main product, showing a molecular ion peak at 240 a.m.u., together with unreacted 1a in experiments (c) and (d) and C-monoacetylated compound 2c and the diacetylated compound 3a in experiment (b)
Summary
Interest in 6-alkyl-3-aryl(alkyl)-1H-pyrazolo[5,1-c][1,2,4] triazoles 1 is commonly attributed to their use as precursors for color photosensitive materials1-3, their role in inks and toners, as ingredients in cosmetics and for their biological activity4-7. All the acetylation reactions of 6-methyl-3-phenyl-1H-pyrazolo[5,1-c][1,2,4]triazole 1a led to the same N-monoacetylated compound, as the main product, showing a molecular ion peak at 240 a.m.u., together with unreacted 1a in experiments (c) and (d) and C-monoacetylated compound 2c and the diacetylated compound 3a in experiment (b). The 1H-NMR spectrum shows δ = 6.17 ppm for H78 while the δ = 12.5 ppm peak (from 6-methyl-3-phenyl-1H-pyrazolo[5,1-c] [1,2,4]triazole 1) assigned to H in -NH-, disappears upon acetylation.
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