Metal Ion Complexes with Pyrazoles, Aziridines and Diaziridines – Synthesis and Biological Activity

A Mechanistic Study on Iron-Based Styrene Aziridination: Understanding Epoxidation via Nitrene Hydrolysis

Transition-metal-catalyzed nitrene transfer reactions are typically performed in organic solvents under inert and anhydrous conditions due to the involved air and water-sensitive nature of reactive intermediates. Overall, this study provides insights into the iron-based ([FeII(PBI)3](CF3SO3)2 (1), where PBI = 2-(2-pyridyl)benzimidazole), catalytic and stoichiometric aziridination of styrenes using PhINTs ([(N-tosylimino)iodo]benzene), highlighting the importance of reaction conditions including the effects of the solvent, co-ligands (para-substituted pyridines), and substrate substituents on the product yields, selectivity, and reaction kinetics. The aziridination reactions with 1/PhINTs showed higher conversion than epoxidation with 1/PhIO (iodosobenzene). However, the reaction with PhINTs was less selective and yielded more products, including styrene oxide, benzaldehyde, and 2-phenyl-1-tosylaziridine. Therefore, the main aim of this study was to investigate the potential role of water in the formation of oxygen-containing by-products during radical-type nitrene transfer catalysis. During the catalytic tests, a lower yield was obtained in a protic solvent (trifluoroethanol) than in acetonitrile. In the case of the catalytic oxidation of para-substituted styrenes containing electron-donating groups, higher yield, TON, and TOF were achieved than those with electron-withdrawing groups. Pseudo-first-order kinetics were observed for the stoichiometric oxidation, and the second-order rate constants (k2 = 7.16 × 10-3 M-1 s-1 in MeCN, 2.58 × 10-3 M-1 s-1 in CF3CH2OH) of the reaction were determined. The linear free energy relationships between the relative reaction rates (logkrel) and the total substituent effect (TE, 4R-PhCHCH2) parameters with slopes of 1.48 (MeCN) and 1.89 (CF3CH2OH) suggest that the stoichiometric aziridination of styrenes can be described through the formation of a radical intermediate in the rate-determining step. Styrene oxide formation during aqueous styrene aziridination most likely results from oxygen atom transfer via in situ iron oxo/oxyl radical complexes, which are formed through the hydrolysis of [FeIII(N•Ts)] under experimental conditions.

Synthesis and Evaluation of Anticonvulsant Activities of 4-Phenylpiperidin- 2-one Derivatives

Background:

Although Antiepileptic Drugs (AEDs) acting on various targets have been applied in the clinic, the efficacy and tolerance of AEDs in the treatment of epilepsy have not significantly improved. Therefore, there is an urgent need to develop some novel chemical moieties with a better safety profile and greater efficacy. We designed and synthesized twenty-seven 4- phenylpiperidin-2-one derivatives. This study aimed to investigate the potential use of a series of 4- phenylpiperidin-2-one derivatives as anticonvulsant drugs.

Methods:

Two experimental methods, Maximal Electroshock (MES) and subcutaneous pentylenetetrazole (scPTZ), were used to evaluate the anticonvulsant activity of the target compounds. Moreover, neurotoxicity (NT) was tested using the rotarod test.

Results:

Compound 7-[4-(trifluoromethyl)phenyl]-6,7-dihydrothieno[3,2-b]pyridin-5-(4H)-one (11; MES, ED50 = 23.7 mg/kg, PI > 33.7; PTZ, ED50 = 78.1 mg/kg, PI > 10.0) showed the best anticonvulsant activity. The results of in vivo γ-aminobutyric Acid (GABA) estimation showed that compound 11 may have an effect on the GABA system. Compound 11 showed significant interactions with residues at the benzodiazepine (BZD)-binding site on GABAA receptors. Most target compounds have favorable blood brain barrier (BBB) permeability and oral bioavailability in predictions using silico molecular properties.

Conclusion:

According to the in vivo and in silico studies, compound 11 stand out as potential anticonvulsant agents for further studies.