Imine-enamine tautomerism of dihydroazolopyrimidines. 5. Steric effects and the tautomeric equilibrium for dihydro-1,2,4-triazolo[1,5-<i>a</i>]pyrimidines

Abstract

The reaction of 3-amino-1,2,4-triazole with β-dimethylaminopropiophenones or unsaturated ketones gives 5,7-disubstituted 4,7(6,7)-dihydro-1,2,4-triazolo[1,5-a]pyrimidines. An increase in the bulk of the substituent at C₍₇₎ in the bicyclic system leads to relative stabilization of the enamine tautomer of these compounds. An X-ray diffraction structural analysis of 7-tert-butyl-5-(4-methoxyphenyl)-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine showed that the introduction of a tert-butyl group into the dihydropyrimidine ring leads to significant loss of planarity of this system.

How to Cite
Desenko, S. M.; Orlov, V. D.; Shishkin, O. V.; Barykin, K. É.; Lindeman, S. V.; Struchkov, Yu. T. Chem. Heterocycl. Compd. 1993, 29, 1163. [Khim. Geterotsikl. Soedin. 1993, 1357.]

For this article in the English edition, see DOI https://doi.org/10.1007/BF00538062