Synthesis and transformations of 4-phenylethynyl- and 4-styrylpyrazolo[5,1-c][1,2,4]triazines

Rearrangements of 3-tert-butyl-8-methyl-4-phenylethynyl-1,4-dihydropyrazolo[5,1-c][1,2,4]triazine derivatives by the action of bases led to the formation of aromatic (E)- or (Z)-4-styryl-functionalized compounds. At the same time, 4-styryl-1,4-dihydropyrazolotriazines did not rearrange to form the expected 4-phenylethylpyrazolo[5,1-c][1,2,4]triazine. The latter was obtained via an alternative route by the addition reaction of phenylethynylmagnesium bromide to 3-tert-butyl-8-methylpyrazolo[5,1-c][1,2,4]triazine, as well as by reduction of double bonds in the ring and side chain of the 4-styryl derivative with subsequent selective oxidation by N-bromosuccinimide. The spectral and X-ray structural data as well as the antimicrobial properties of the synthesized compounds are discussed.