New Application of Heterocyclic Diazonium Salts: Synthesis of New Pyrazolo[3,4‐d][1,2,3]triazin‐4‐ones

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 of Pyrazole-Carboxamides and Pyrazole-Carboxylic Acids Derivatives: Simple Methods to Access Powerful Building Blocks

Abstract:

Hybrid systems containing pyrazole moiety show a wide spectrum of biological activities. To access novel hybrids with pyrazole ring, in this work we synthesized twenty pyrazole-carboxylic acids and twenty pyrazole-carboxamides, using simple synthetic methods, to be used as building blocks in the development of new structures.

Facile Synthesis and Antimicrobial Activities of Novel 1,4-Bis(3,5-dialkyl-4H-1,2,4-triazol-4-yl)benzene and 5-Aryltriaz-1-en-1-yl-1-phenyl-1H-pyrazole-4-carbonitrile Derivatives

A group of novel 1,4-bis(3,5-dialkyl-4H-1,2,4-triazol-4-yl)benzene and 5-aryltriaz-1-en-1-yl-1-phenyl-1H-pyrazole-4-carbonitrile derivatives have been successfully synthesized and characterized by spectroscopic analyses. The triazenes were obtained in moderate yield by a coupling reaction between 5-aminopyrazol-4-carbonitrile and aryl diazonium chlorides, and their structures were confirmed by detecting the CN functional group in both IR and 13C NMR spectra. Conversely, the novel 1,4-bis(3,5-dialkyl-4H-1,2,4-triazol-4-yl)benzene derivatives were obtained using a previously unreported and facile pathway starting with p-phenylenediamine with selected triethyl orthoalkylates and then hydrazine monohydrate, followed by refluxing in triethyl orthoalkylates. The structure of the methyl derivative was confirmed by X-ray analysis. The synthesized compounds were tested and evaluated as antimicrobial agents.

Synthesis, antitumor evaluation and microarray study of some new pyrazolo[3,4-d][1,2,3]triazine derivatives

Design and synthesis of new anticancer scaffolds; pyrazolo[3,4-d][1,2,3]triazine derivatives, is a promising solution to overcome drug resistance problem. A series of (E)-2-cyano-N-(aryl)-3-methylthio-3-(substituted-amino)acrylamides 3a-e was synthesized and transformed to the 3-aminopyrazole derivatives 4a-e which were then transformed to the target pyrazolotriazinones 6a-e. All compounds were evaluated for their anticancer activity against three different cancer cell lines namely Huh-7, Panc-1 and CCRF. Compounds 3a, 3c, 6a and 6c showed excellent anticancer activity against Huh-7 cell line (IC₅₀: 4.93-8.84 μM vs doxorubicin 5.43 μM). Similarly, compounds 6a and 6d showed excellent activities against Panc-1 cells (IC₅₀: 9.91 μM and 4.93 μM vs doxorubicin 6.90 μM). Caspase-Glo 3/7 assay was done and the results revealed that the pro-apoptotic activity of the target compounds could be due to the stimulation of caspases 3/7. Microarray experiment for Huh-7 cells treated with 6c was performed to search for other molecular changes. SLC26A3, UGT1A1, UGT2B15, UGT2B7, DNASE1, MUCDH1 and UGT2B17 were among the up-regulated genes, while, GIP3, TAGL, THBS1, IFI27, FSCN1 and SOCS2 were among the most extensively down-regulated genes. These genes belong to apoptosis, metabolism, cell cycle, tumor growth and suppressor genes. Finally, pyrazolo[3,4-d][1,2,3]triazine derivatives could be potent anticancer drugs in the future.

A Novel Synthesis of 1,2,3-Benzotriazinones from 2-(o-Aminophenyl)oxazolines

1,2,3-Benzotriazinones were synthesized in excellent yields by the reaction of 2-(o-aminophenyl)oxazolines and isoamyl nitrite in methanol. The crystal structure of the acetyl derivative of one of the 1,2,3-benzotriazinones provided additional support for the spectroscopic structural characterization of the title compounds.

On the Route to the Photogeneration of Heteroaryl Cations. The Case of Halothiophenes

2-Chloro-, 2-bromo-, and 2-iodothiophenes undergo photochemical dehalogenation via the triplet state. In the presence of suitable π-bond nucleophiles, thienylation occurs with modest yield from chloro and bromo derivatives (via photogenerated triplet 2-thienyl cation). Specific trapping by using oxygen along with computational analysis carried out by means of a density functional method support that, in the case of iodo derivatives, homolytic thienyl-I bond fragmentation occurs first and heteroaryl cations are formed by electron transfer within the triplet radical pair, thus opening an indirect access to such cations.