CRYSTAL STRUCTURE OF 3-tert-BUTYL- PYRAZOLO[5,1-с][1,2,4]TRIAZINE-3,4-DIYL DICARBOXYLATES

By single crystal X-ray diffraction the structures of (trans-)7-R¹-8-methyl-3-tert-butyl-3,4-dihydropyrazolo[5,1-с][1,2,4]triazine-3,4-diyl dibenzoates 3а, 4а (R¹ = H, Br) and diacetate 3b (R¹ = H) are studied for the first time. The compounds are synthesized by oxidative bromination of respective 1,4-dihydropyrazolo[5,1-c][1,2,4]triazines in the presence of carboxylic acids. Dicarboxylates adopt a twist-conformation with the equatorial (3a) or axial (3b, 4a) orientation of tert-butyl groups relative to the heterocycle. In the case of diacetate 3b, a decrease in the thermal motion of the O4–C16–C17 fragment along with a decrease in the unit cell volume are observed on cooling from 300 K to 200 K. Bond lengths, torsion angles, and molecular packings in the crystals are discussed.

Synthesis and crystal structures of 7,8-bromo (dibromo)-3-tert-butylpyrazolo[5,1-c][1,2,4]triazines

Single crystal structures in a series of 7-bromo-, 8-bromo-, and 7,8-dibromo-3-tert-butylpyrazolo[5,1-c][1,2,4]triazin-4(1H)-ones have been investigated by X-ray diffraction. Novel 7-bromo- and 7,8-dibromo-3-tert-butylpyrazolo[5,1-c][1,2,4]triazines were synthesized by reduction of triazine carbonyl with dehydrative aromatization in acidic media, and their XRD structural features were compared with that of the 4-oxo analogs. The lengths and bond angles and the packing of molecules in crystals have been considered. Non-valence interactions for some of the studied compounds were observed. Correlations between the presence of bromine atoms at different positions and structural features are determined.

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SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11224-021-01768-0.