Abstract
The position of the tautomeric equilibrium in unsubstituted 1,2,4-triazolo[1,5-a] benzimidazole, as well as in its 2-methyl and 2-phenyl derivatives, was investigated by UV, IR, and PMR spectroscopy and by determination of the ionization constants. In all cases the amount of the 4H tautomer in the equilibrium mixture is two to three orders of magnitude greater than the amount of the 3H tautomer, while signs of the existence of the 1 H form are not observed. The synthesis of unsubstituted triazolo [1,5-a]-benzimidazole was accomplished for the first time. The alkylation of the indicated triazolo [1,5-a]benzimidazoles was studied and a relationship between the regiospecificity of this reaction and the position of the tautomeric equilibrium was established.
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Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 209–220, February, 1989.
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Kuz'menko, V.V., Kuz'menko, T.A., Pozharskii, A.F. et al. 1,2,4-Triazolo[1,5-a]benzimidazoles: Tautomerism and alkylation. Chem Heterocycl Compd 25, 168–179 (1989). https://doi.org/10.1007/BF00479912
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DOI: https://doi.org/10.1007/BF00479912