Synthesis of substituted 5-hydroxypyrazolo[1,5-a]quinoxalin-4-ones

Copper-Catalyzed Oxidative [3 + 2]-Annulation of Quinoxalin-2(1H)-one with Oxime Esters toward Functionalized Pyrazolo[1,5-a]quinoxalin-4(5H)-ones as Opioid Receptor Modulators

Pyrazolo[1,5-a]quinoxalin-4(5H)-one derivatives as novel opioid receptor modulators have been synthesized via copper-catalyzed oxidative [3 + 2]-annulation of quinoxalin-2(1H)-one and oxime-O-acetates. This hydrazine-free C-C and N-N bond formation strategy starts with the generation of C₂N₁ synthon using oxime acetate, which reacts in a [3 + 2] manner with quinoxalin-2(1H)-one, followed by oxidative aromatization. The synthesized compounds were tested against opioid receptors, of which eight compounds exhibited an antagonistic effect with EC₅₀ < 5 μM at various opioid receptors. Molecular docking studies were performed to identify the binding of active pyrazolo[1,5-a]quinoxalin-4(5H)-one ligands with hKOR protein. Docking results indicated that compounds 3d and 3g participate in hydrogen bonding with the hydroxyl group of T111 of the active site pocket residue.

Synthesis and Photoluminescent Properties of 2-(3-Carboxymethylindazol-1-yl)anilines

Abstract

A two-stage method for the preparation of 2-(3-carboxymethylindazol-1-yl)anilines using the N-arylation reaction of 3-carboxymethylindazoles with o-nitrohaloarenes and subsequent reduction of nitro-containing intermediates with tin(II) chloride was developed. The experimental results showed that the use of the synthesized compounds as fluorophores in the visible region of the spectrum is promising.

Investigation of pyrazolo[1,5-a]quinoxalin-4-ones as novel monoamine oxidase inhibitors

The monoamine oxidase (MAO) enzymes are key metabolic enzymes of neurotransmitter and other bioactive amines, and represent important drug targets for the treatment of neuropsychiatric and neurodegenerative disorders. Inhibitors of MAO are established medications for the treatment of depression and Parkinson's disease, and may have future roles in other disease states such as the therapy of prostate cancer, cardiovascular disease and inflammatory diseases. Based on these considerations, the present study synthesizes a series of 22 pyrazolo[1,5-a]quinoxalin-4-one derivatives and evaluated them as potential inhibitors of human MAO-A and MAO-B. The results show that 8 derivatives inhibit MAO-A, and 3 derivatives inhibit MAO-B with IC₅₀ values in the submicromolar range (<1 µM). The most potent MAO-A inhibitor, N-[5-(acetyloxy)-2-(4-chlorophenyl)-4-oxo-4,5-dihydropyrazolo[1,5-a]quinoxalin-7-yl]acetamide (7c), exhibit an IC₅₀ value of 0.028 µM and displays 50-fold selectivity for MAO-A over MAO-B. The most potent MAO-B inhibitor, 2-(4-methylphenyl)-4-oxo-4,5-dihydropyrazolo[1,5-a]quinoxaline-7-carbonitrile (4f), exhibit an IC₅₀ value of 0.617 µM and displays 8-fold selectivity for MAO-B. This is the first report of MAO inhibition by pyrazolo[1,5-a]quinoxalin-4-one derivatives, and this study concludes that these compounds are suitable leads for the future development of MAO inhibitors, particularly of the MAO-A isoform.