Imine-enamine tautomerism of dihydroazolopyrimidines 5. Steric effects and the tautomeric equilibrium for dihydro-1,2,4-triazolo[1,5-a]pyrimidines |
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Authors: | S M Desenko V D Orlov O V Shishkin K É Barykin S V Lindeman Yu T Struchkov |
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Institution: | (1) Kharkov State University, 310077 Kharkov;(2) Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow |
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Abstract: | The reaction of 3-amino-1,2,4-triazole with -dimethylaminopropiophenones or unsaturated ketones gives 5,7-disubstituted 4,7(6,7)-dihydro-1,2,4-triazolo1,5-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-triazolo1,5-a]pyrimidine showed that the introduction of a tert-butyl group into the dihydropyrimidine ring leads to significant loss of planarity of this system.For Communication 4, see 1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1357–1363, October, 1993. |
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