Regioselective synthesis of 4,7,8,9-tetrahydro-2 H -pyrazolo[3,4- b ]quinolin-5(6 H )-ones. Mechanism and structural analysis

1H-Pyrazolo[3,4-b]quinolines: Synthesis and Properties over 100 Years of Research

This paper summarises a little over 100 years of research on the synthesis and the photophysical and biological properties of 1H-pyrazolo[3,4-b]quinolines that was published in the years 1911–2021. The main methods of synthesis are described, which include Friedländer condensation, synthesis from anthranilic acid derivatives, multicomponent synthesis and others. The use of this class of compounds as potential fluorescent sensors and biologically active compounds is shown. This review intends to summarize the abovementioned aspects of 1H-pyrazolo[3,4-b]quinoline chemistry. Some of the results that are presented in this publication come from the laboratories of the authors of this review.

l-Proline as an efficient enantioinduction organo-catalyst in the solvent-free synthesis of pyrazolo[3,4-b]quinoline derivatives via one-pot multi-component reaction

The role of l-proline as an efficient organo-catalyst for the three-component synthesis of pyrazoloquinolinones involving dimedone, 3-methyl-1H-pyrazol-5-amine and various aryl aldehydes under mild solvent-free condition is reported.

A new inorganic–organic hybrid material Al-SBA-15-TPI/H6P2W18O62 catalyzed one-pot, three-component synthesis of 2H-indazolo[2,1-b]phthalazine-triones

Al-SBA-15-TPI/H₆P₂W₁₈O₆₂ is introduced as an effective catalyst for the one-pot synthesis of indazolo-phthalazine-triones. The catalyst could be easily separated without noticeable reduction in activity.

SAR156497, an exquisitely selective inhibitor of aurora kinases

The Aurora family of serine/threonine kinases is essential for mitosis. Their crucial role in cell cycle regulation and aberrant expression in a broad range of malignancies have been demonstrated and have prompted intensive search for small molecule Aurora inhibitors. Indeed, over 10 of them have reached the clinic as potential anticancer therapies. We report herein the discovery and optimization of a novel series of tricyclic molecules that has led to SAR156497, an exquisitely selective Aurora A, B, and C inhibitor with in vitro and in vivo efficacy. We also provide insights into its mode of binding to its target proteins, which could explain its selectivity.

Microwave induced three-component synthesis and antimycobacterial activity of benzopyrazolo[3,4-b]quinolindiones

Three series of novel 4-arylbenzo[h]pyrazolo[3,4-b]quinolin-5,6-diones 4, 7 and 9 have been efficiently obtained in good yields by three-component microwave assisted reaction between aminopyrazoles 1 or 6 (both 1-phenyl and 1-H substituted), 2-hydroxynaphthoquinone 2 and benzaldehydes 3. Compounds 4, 7 and 9 have been evaluated against fifteen Mycobacterium spp strains, and six of them have shown antimycobacterial activity. The highest inhibitory activity with MIC ≤2 μg/mL for three of these compounds (4a, 4b and 4g) was related with their highest lipophilicity and lesser polarity within these series.

Combinatorial synthesis of pyrrolo[3,2-f]quinoline and pyrrolo[3,2-a]acridine derivatives via a three-component reaction under catalyst-free conditions

A combinatorial synthesis of pyrrolo[3,2-f]quinoline and pyrrolo[3,2-a]acridine derivatives is described as a three-component reaction of aromatic aldehyde, 1H-indol-5-amine, and 1,3-dicarbonyl compounds under catalyst-free conditions. The 1,3-dicarbonyl compounds include 5,5-dimethylcyclohexane-1,3-dione, cyclopentane-1,3-dione, and 2H-indene-1,3-dione. It is interesting that the designed reactions gave aromatized or unaromatized products, which depend on the reaction temperature and reactants of 1,3-dicarbonyl compounds.

Multi-component one-pot synthesis and antimicrobial activities of 3-methyl-1,4-diphenyl-7-thioxo-4,6,8,9-tetrahydro-pyrazolo[5,4-b]pyrimidino[5,4-e]pyridine-5-one and related derivatives

The synthesis of 3-methyl-1,4-diphenyl-7-thioxo-4,6,8,9-tetrahydropyrazolo[5,4-b] pyrimidino[5,4-e]pyridine-5-one (6) was achieved by two different one-pot multi-component synthesis (one-pot three-component and one-pot four component synthesis). Mono and dialkylation of 6 under different conditions gave compounds 7–11. The hydrazine 12 produced from reaction of 9 with N₂H₄ was subjected to reactions with some aromatic aldehydes, ethyl acetoacetate, acetyl acetone, ethyl cyanoacetate and triethyl orthoformate to give 13–17, respectively. Compound 12 upon reaction with CS₂, nitrous acid, benzoin, chloroacetone and phenacyl bromide gave 18,20,21,22. Alkylation of 18 with ethyl iodide, ethyl chloroacetate and phenacyl bromide gave 19a–c. The antibacterial and antifungal activities of selected derivatives were evaluated.

Regioselectivity in the multicomponent reaction of 5-aminopyrazoles, cyclic 1,3-diketones and dimethylformamide dimethylacetal under controlled microwave heating

The multicomponent reaction of 5-aminopyrazole derivatives with cyclic 1,3-dicarbonyl compounds and dimethylformamide dimethylacetal (DMFDMA) in DMF at 150 °C under controlled microwave heating afforded regioselectively 8,9-dihydropyrazolo[1,5-a]quinazolin-6(7H)-ones 6 rather than the corresponding dihydropyrazolo[5,1-b]quinazolin-8(5H)-ones 4.

5-(4-Chloro-phen-yl)-1-methyl-3-phenyl-3,6,8,9-tetra-hydro-pyrazolo-[3,4-b]thio-pyrano[4,3-d]pyridine

The title compound, C₂₂H₁₈ClN₃S, was synthesized by the reaction of 4-chloro­benzaldehyde, tetra­hydro­thio­pyran-4-one and 3-methyl-1-phenyl-1H-pyrazol-5-amine in acetic acid without a catalyst. The pyridine and pyrazole rings are almost coplanar, the dihedral angle between their mean planes being 2.50 (1)°. The thio­pyran ring exhibits an envelope conformation. The crystal packing is stabilized by inter­molecular C—H⋯Cl hydrogen bonds and by C—H⋯π and π–π inter­actions [centroid–centroid distances of 3.825 (2) Å between pyridine rings and 3.557 (2) Å between pyrazole and pyridine rings.

Synthesis of novel 1,2,5-trisubstituted benzimidazoles as potential antitumor agents

Novel methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(aryl)-1H-benzo[d]imidazole-5-carboxylates 11 were synthesized by following a four-step strategy involving a nucleophilic aromatic displacement (S(N)Ar) and a solvent free approach as key steps for the formation of the desired products. Structure of intermediates and products were confirmed by X-ray diffraction as well as the tautomeric rearrangement suffered by the pyrazole moiety during the curse of the final cyclization process. Several of the obtained compounds were screened by the US National Cancer Institute (NCI) for their ability to inhibit 60 different human tumor cell lines. Products 11b and 11n exhibited the highest activity against a range of cancer cell lines with remarkable values in panels of Non-Small Cell Lung Cancer, Melanoma and Leukemia, with GI(50) range of 1.15-7.33 μM and 0.167-7.59 μM, respectively, and suitable LC(50) with values greater than 100 μM.

A convenient ultrasound-promoted regioselective synthesis of fused polycyclic 4-aryl-3-methyl-4,7-dihydro-1H-pyrazolo[3,4-b]pyridines

Fused polycyclic 4-aryl-3-methyl-4,7-dihydro-1H-pyrazolo[3,4-b]pyridines were obtained in a three-component regioselective reaction of 5-amino-3-methyl-1H-pyrazole, 2H-indene-1,3-dione and arylaldehydes in ethanol under ultrasound irradiation. This rapid method produced the products in short reaction times (4-5min) and excellent yields (88-97%).