Metalated azolo[1,2,4]triazines. II. Generation, C(4)-substituent dependent stability and electrophile trapping of 7-lithiopyrazolo[5,1-c][1,2,4]triazines

Crystal Structure Analysis of 4-Oxo, 4-hydroxy- and 4-alkyl-7-bromopyrazolo[5,1-c][1,2,4]triazines

The crystal structures of 8-R1-7-bromo-3-tert-butyl-1-R2-pyrazolo[5,1-c][1,2,4]triazin-4(1H)-ones 1a-c, 2a,c (R1 = CN, CO2Et, NO2, R2 = H, 1:1 and 3:1 solvates with DMSO; R1 = CN, CO2Et, R2 = CH2Boc), 8-R1-7-bromo-3-tert-butyl-1-R2-1,4-dihydropyrazolo[5,1-c][1,2,4]triazin-4-ols 3a,b (R1 = CN, R2 = n-Bu; R1 = Br, R2 = CH2Boc), 1,4-dihydro- and aromatic 7-R3-3-tert-butyl-4-R4-8-methylpyrazolo[5,1-c][1,2,4]triazines 5a,b, 6 (R3 = H, R4 = n-Pr; R3 = Br, R4 = n-Bu) were investigated by X-ray diffraction analysis. The structural preferences and different packing modes based on the intermolecular interactions were analyzed by the Hirshfeld surface and energy framework analysis.

Graphical Abstract

The crystal structures of ten 3-tert-butyl-4-oxo, 4-hydroxy- and 4-alkyl-7-bromopyrazolo[5,1-c][1,2,4]triazines including non-solvated, 1:1 and 3:1 solvates with DMSO were investigated by single crystal X-ray diffraction, Hirshfeld surface and energy framework analyses.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10870-022-00973-x.

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.

Pyrazolotriazines: Biological activities, synthetic strategies and recent developments

Heterocyclic compounds create an important class of molecules that demonstrates various chemical spaces for the definition of effective medicines. Many N-heterocycles display numerous biological activities. Among condensed heterocycles, pyrazolotriazine derivatives have received the attention of researchers owing to the extensive spectrum of biological activities. The reactivity of identified compounds was similar to the free azoles and triazines. The pyrazolotriazine scaffold exhibited antiasthma, antiinflammatory, anticancer, antithrombogenic activity and showed activity for major depression and pathological anxiety. Pyrazolotriazine derivatives also exhibited antibacterial, anticancer, antimetabolites, antidiabetic, antiamoebic, anticonvulsant, antiproliferative activity, human carbonic anhydrase inhibition, cyclin-dependent kinase 2 inhibition, tyrosinase and urease inhibition, MAO-B inhibition, TTK inhibition, thymidine phosphorylase inhibition, tubulin polymerization inhibition, protoporphyrinogen oxidase inhibition, GABA_A agonistic activity, hCRF1 receptor antagonistic activity, and CGRP receptor antagonistic activity. This paper structurally categorized various pyrazolotriazines to isomeric classes into six groups that containing pyrazolo [1,5-d] [1,2,4] triazine, pyrazolo [5,1-c] [1,2,4] triazine, pyrazolo [3,4-e] [1,2,4] triazine, pyrazolo [4,3-e] [1,2,4] triazines, pyrazolo [1,5-a] [1,3,5] triazine, and pyrazolo [3,4-d] [1,2,3] triazine and expressed biological activity, the synthetic procedures for each class of pyrazolotriazines, structure-activity relationship and their mechanism of action. Generally, this review summarily indicated the past and present studies about the discovery of new lead compounds with good biological activity.

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.

GRAPHICAL ABSTRACT

SUPPLEMENTARY INFORMATION

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