Iodine-Catalyzed Radical C-H Amination of Nonaromatic Imidazole Oxides: Access to Cyclic α-Aminonitrones

A straightforward cross-dehydrogenative coupling approach to incorporate alicyclic amino residues into the structure of model cyclic aldonitrones, 2H-imidazole oxides, is reported. The elaborated C(sp2)-H functionalization is achieved by employing cyclic amines in the presence of the I2-tert-butyl hydroperoxide (TBHP) reagent system. As a result, a series of 19 novel heterocyclic derivatives were obtained in yields of up to 97%. A mechanistic study involving electron paramagnetic resonance spectroscopic experiments allowed the radical nature of the reaction to be confirmed. In particular, the envisioned mechanistic rationale comprises N-iodination of a cyclic amine, followed by N-I bond homolysis of the resulting intermediate and subsequent amination of the nitrone moiety via the newly generated nitrogen-centered radical.

One-Pot Transformation of Aldehydes to Ketones via Minisci-Type Reaction of Imines

A method for the conversion of aldehydes to ketones via the preliminary formation of aldiminines is described. The imines are involved in acid promoted Minisci-type reaction with alkyl radicals generated from esters of N-hydroxylphthalimide under photoredox conditions. Aminyl radical cations formed after the addition of the iminium ions are believed to be key intermediates, which determine the reaction outcome.

Indolyl-Derived 4H-Imidazoles: PASE Synthesis, Molecular Docking and In Vitro Cytotoxicity Assay

The strategy of the nucleophilic substitution of hydrogen (SNH) was first applied for the metal-free C-H/C-H coupling reactions of 4H-imidazole 3-oxides with indoles. As a result, a series of novel bifunctional azaheterocyclic derivatives were obtained in yields up to 95%. In silico experiments on the molecular docking were performed to evaluate the binding possibility of the synthesized small azaheterocyclic molecules to the selected biotargets (BACE1, BChE, CK1δ, AChE) associated with the pathogenesis of neurodegenerative diseases. To assess the cytotoxicity for the synthesized compounds, a series of in vitro experiments were also carried out on healthy human embryo kidney cells (HEK-293). The leading compound bearing both 5-phenyl-4H-imidazole and 1-methyl-1H-indole moieties was defined as the prospective molecule possessing the lowest cytotoxicity (IC50 > 300 µM on HEK-293) and the highest binding energy in the protein–ligand complex (AChE, −13.57 kcal/mol). The developed compounds could be of particular interest in medicinal chemistry, particularly in the targeted design of small-molecule candidates for the treatment of neurodegenerative disorders.

A BF3-mediated C–H/C–Li coupling of 1,3,7-triazapyrene with 2-thienyllithium in the design of push–pull fluorophores and chemosensors for nitroaromatics

A BF3-mediated strategy of oxidative nucleophilic substitution of hydrogen affords mono- and bis-substituted thiophene-derived 1,3,7-triazapyrene fluorophores of interest in the design of luminescent materials and chemosensors for nitroaromatics.

Design and Antioxidant Properties of Bifunctional 2H-Imidazole-Derived Phenolic Compounds-A New Family of Effective Inhibitors for Oxidative Stress-Associated Destructive Processes

The synthesis of inhibitors for oxidative stress-associated destructive processes based on 2H-imidazole-derived phenolic compounds affording the bifunctional 2H-imidazole-derived phenolic compounds in good-to-excellent yields was reported. In particular, a series of bifunctional organic molecules of the 5-aryl-2H-imidazole family of various architectures bearing both electron-donating and electron-withdrawing substituents in the aryl fragment along with the different arrangements of the hydroxy groups in the polyphenol moiety, namely derivatives of phloroglucinol, pyrogallol, hydroxyquinol, including previously unknown water-soluble molecules, were studied. The structural and antioxidant properties of these bifunctional 5-aryl-2H-imidazoles were comprehensively studied. The redox transformations of the synthesized compounds were carried out. The integrated approach based on single and mixed mechanisms of antioxidant action, namely the AOC, ARC, Folin, and DPPH assays, were applied to estimate antioxidant activities. The relationship “structure-antioxidant properties” was established for each of the antioxidant action mechanisms. The conjugation effect was shown to result in a decrease in the mobility of the hydrogen atom, thus complicating the process of electron transfer in nearly all cases. On the contrary, the conjugation in imidazolyl substituted phloroglucinols was found to enhance their activity through the hydrogen transfer mechanism. Imidazole-derived polyphenolic compounds bearing the most electron-withdrawing functionality, namely the nitro group, were established to possess the higher values for both antioxidant and antiradical capacities. It was demonstrated that in the case of phloroglucinol derivatives, the conjugation effect resulted in a significant increase in the antiradical capacity (ARC) for a whole family of the considered 2H-imidazole-derived phenolic compounds in comparison with the corresponding unsubstituted phenols. Particularly, conjugation of the polyphenolic subunit with 2,2-dimethyl-5-(4-nitrophenyl)-2H-imidazol-4-yl fragment was shown to increase ARC from 2.26 to 5.16 (10⁴ mol-eq/L). This means that the considered family of compounds is capable of exhibiting an antioxidant activity via transferring a hydrogen atom, exceeding the activity of known natural polyphenolic compounds.