Synthesis and photolysis of 3-tert-butyl-4-oxy(mercapto)-1,4-dihydropyrazolo[5,1-c][1,2,4]triazines

Reactions of 3-tert-butyl- or 3,4-di-tert-butyl-substituted 8-methylpyrazolo[5,1-c][1,2,4]-triazines with trifluoroacetic anhydride afforded 1-(2,2,2-trifluoroacetyl)-1,4-dihydropyrazolo-[5,1-c][1,2,4]triazin-4-yl 2,2,2-trifluoroacetates. The treatment with H2X and RXH (X = O or S; R = Me or Et) of covalent trifluoroacetate that does not contain the Bu-t group at the C(4) atom allowed us to synthesize 1-(3-tert-butyl-4-R-pyrazolo[5,1-c][1,2,4]triazin-1(4H)-yl)-2,2,2-trifluoroethan-1-ones. The structure of 4-ethylthio derivative was fully established by the single-crystal X-ray diffraction analysis. The UV irradiation of obtained 2,2,2-trifluoroethan-1-ones leads to the aromatization of triazine ring. The UV photolysis of 1-trifluoroacetyl-4-hydroxy derivative has been proposed as a novel method for the photogeneration of acidity. Antimicrobial and antifungal activities of the synthesized compounds were evaluated.