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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.

A different type of MnO2-induced oxidative cyclization of dihydrotriazines has been developed. These dihydrotriazines are considered as a “formal” Schiff’s base. This method provided easy access to naphthofuro-fused triazine via the C-C/C-O oxidative coupling reaction. The reaction sequence comprised the nucleophilic addition of 2-naphthol or phenol to 1,2,4-triazine, followed by oxidative cyclization. The scope and limitations of this novel coupling reaction have been investigated. Further application of the synthesized compound has been demonstrated by synthesizing carbazole-substituted benzofuro-fused triazines. The scalability of the reaction was demonstrated at a 40 mmol load. The mechanistic study strongly suggests that this reaction proceeds through the formation of an O-coordinated manganese complex.

A different type of MnO

Because of the development of radiation processing of food and agricultural products it requires new methods of control over the processing and turnover of products. A promising method for monitoring is EPR spectrometry. This research presents the results of a study of the radiation induced EPR signal in eggshells. The URT-0.5 (0.5 MeV) and UALR-10-10 S2 (10 MeV) accelerators were used for irradiation. It shows the kinetics of radicals over time. The dependences of the EPR signal intensity on the absorbed dose were obtained, and a comparative analysis of the irradiation of chicken eggs with different energies was performed. The kinetics of radicals over time and the dependence of the intensity of the EPR signal on the absorbed dose are shown. A comparative analysis of the irradiation of chicken eggs with different energies is carried out.

The results of studying electrochemical conversions of 7-R-3-X-1,2,4-triazolo[5,1-c][1,2,4]-triazin-4-ones (Triazavirin® and its derivatives) using cyclic voltammetry, chronoamperometry, and ESR spectroscopy are presented. The derivatives of 7-R-3-X-1,2,4-triazolo[5,1-c][1,2,4]-triazin-4-ones were found to be capable of electrochemical reducing in the potential range from −0.16 to −0.68 V (vs Ag/AgCl) in a Britton—Robinson buffer at pH 2–12. At the potentials of the first electroreduction step at pH 2–6, the main process of transformations is the four-electron scheme of reduction of the nitro group of Triazavirin®. The adduct of the radical substances with the spin probe N-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)-2-methylpropanamide was registered after the preliminary generation of the Triazavirin® radical anion at −0.5 V vs Ag/AgCl in an acidic medium. A linear dependence of the current of the first electroreduction step of the Triazavirin® on the concentration was obtained at pH 2 (linearity range from 10−4 to 1.6 · 10−2 mol L−1, I = −1.93 · C, R2 = 0.9977).

An original approach to achieve the C(sp2)–H azolation of cyclic aldonitrones mediated by Selectfluor® has first been employed. By exploiting a metal-free, visible-light-promoted cross-dehydrogenative C–N coupling reaction between model aldonitrones, 2H-imidazole 1-oxides, and NH-containing azoles, a series of novel azaheterocyclic derivatives have been obtained in yields up to 94%. The elaborated protocol has proved to be appropriate for gram-scale processes and displayed potential for utilization in the synthesis of novel structural analogues of lanabecestat. Besides, mechanistic studies have revealed that this coupling reaction is likely to proceed via a nitroxide-involving radical pathway, encompassing a chain of electron transfer events, such as hydrogen atom transfer (HAT) and single electron transfer (SET).

New ethynyl derivatives were synthesized from 5-(benzothiazol-2-yl)-1-(4-iodophenyl)-3-phenyl-6-vinyl(phenyl)verdazyls using Sonogashira cross-coupling reactions carried out in two stages. The resulted radicals were characterized using EPR, IR, UV/Vis spectroscopy, mass spectrometry, and cyclic voltammetry. Electronic structure calculations using quantum chemistry methods were performed to analyze some experimental results.

C,C-Coupling of indole-3-carbaldehyde arylhydrazones with quinazoline in trifluoroacetic acid has occurred at position 5 or 7′ of the hydrazone molecule and has afforded the σ-adducts. The C,C-coupling has been accompanied by a change in the E-configuration of the C=N bond of the starting hydrazones to the Z-configuration in the formed quinazoline trifluoroacetyl hydrazides.

The main advances in the synthesis and studies of the properties of new stable heterocyclic verdazyl radicals and verdazyl radical coordination chemistry are reviewed. The promising applications of these radicals are also discussed.

This article presents the results of a study of electrochemical transformations in aqueous and aprotic media of 5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidinide l-arginine monohydrate (1a, Triazid) obtained by electrochemical methods and ESR spectroscopy. The effect of pH on the current and the reduction potential of 1a in an aqueous Britton–Robinson buffer solution was studied. It was found that 1a is irreversibly reduced in aqueous acidic media on a glassy carbon electrode in one stage with the participation of six electrons and the formation of 5-methyl-6-amino-7-oxo-1,2,4-triazolo[1,5-a]pyrimidin. The electroreduction of 1a in DMF on a background of tetrabutylammonium salts proceeds in two stages, controlled by the kinetics of second-order reactions. In the first stage, the reduction of 1a is accompanied by protonation by the initial compound of the basic intermediate products formed in the electrode reaction (self-protonation mechanism). The second quasi-reversible stage of the electroreduction 1a corresponds to the formation of a dianion radical upon the reduction of the heterocyclic anion 5-methyl-6-nitro-7-oxo-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidin, which is formed upon the potentials of the first peak. The ESR spectrum of the radical dianion was recorded upon electroreduction of Triazid in the presence of Bu4NOH. The effect of the formation of ion pairs on the reversibility of the second peak of the 1a transformation is shown. A change in the rate and regioselectivity of the protonation of the dianion radical in the presence of Na+ and Li+ ions is assumed. The results of studying the electroreduction of 1a by ESR spectroscopy with a TEMPO trap make it possible to assume the simultaneous formation of both a nitroxyl radical and a radical with the spin density localized on the nitrogen at the 4 position of the six-membered ring. © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Funding: This work was supported by the Russian Foundation for Basic Research (RFBR, project No. 19-29-08015 mk).

New 2-(5-aryl-6-R-3-phenyl-5,6-dihydro-4H-1,2,4,5-tetrazin-1-yl)-1,3-benzothiazoles were synthesized from the corresponding formazans by alkylation and subsequent cyclization of N-alkyl derivatives. The products were characterized by 1H and 13C NMR, IR, and mass spectra and X-ray diffraction data. Electrochemical properties and antioxidant activity of the synthesized benzothiazole derivatives were studied.

A brief list of the main directions in radiation processes using ionizing radiation in a wide range of doses and energies is given. The necessity of monitoring doses in irradiated objects and diagnosing radiation fields is substantiated. It is noted that in world practice, these problems are solved with the help of dosimetric EPR systems and detectors based on L-α-alanine. Using the example of sterilizing medical devices by radiation from an electron accelerator, a series of experimental results have been obtained that confirm the possibility of using polytetrafluoroethylene as a detector in dosimetric EPR systems for monitoring radiation processes.

A sequence of alkylation, cyclization, and oxidation reactions was used to convert 5-aryl-1-(benzo[d]thiazol-2-yl)-3-phenylformazans into 6-alkyl-5-aryl-1-(benzo[d]thiazol-2-yl)-3-phenylverdazyls and 5-aryl-1-(benzo[d]thiazol-2-yl)-3-phenyl-6-vinylverdazyls. The paramagnetic and electrochemical properties of the obtained compounds were studied.

Reactions of quinoxalines and quinoxalin-2-ones with C-nucleophiles under acid-catalysis conditions gave products from nucleophilic substitution of hydrogen. Substitution of F atoms in the aromatic core of quinoxalines was studied. Antibacterial and fungistatic activity of the synthesized compounds was studied.

In this work a qualitative analysis is carried out by EPR methods in the middle region dose level. Using the EPR method it was found that the irradiated materials contain a small amount of steam, magnetic centers of free radicals. However, after irradiation its number increases respectively to the dose and electron energy. It is important that the EPR method allows establishing not only the fact of product irradiation but also the value of the absorbed dose.

Experimental facts on the mechanism of the direct oxidative photocatalytic C H/C H coupling of azines with (hetero)aromatic nucleophiles, proceeding in the presence of TiO2 as a photocatalyst, have been obtained by using EPR spectroscopy and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), N-(1-hydroxy-2,2,6,6-tetramethylpiperidin-4-yl)-2-methylpropanamide (TMT-H), as spin trap reagent and spin probe, respectively. The formation of the superoxide radical anion (O2 −) and N-centered radicals has been detected for the first time for the SNH transformations.

Chemical and physical processes occurring within the nanochannels of mesoporous materials are known to be determined by both the chemical nature of the solution inside the pores/channels as well as the channel surface properties, including surface electrostatic potential. Such properties are important for numerous practical applications such as heterogeneous catalysis and chemical adsorption including chromatography. However, for solute molecules diffusing inside the pores, the surface potential is expected to be effectively screened by counter ions for the distances exceeding the Debye length. Here, we employed electron paramagnetic resonance spectroscopy of ionizable nitroxide spin probes to experimentally examine the conditions for the efficient electrostatic surface potential screening inside the nanochannels of chemically similar silica-based mesoporous molecular sieves (MMS) filled with water at ambient conditions and a moderate ionic strength of 0.1 M. Three silica MMS having average channel diameters of D = 2.3, 3.2, and 8.1 nm (C 12 MCM-41, C 16 MCM-14, and SBA-15, respectively) were chosen to investigate effects of the channel diameter at the nanoscale. The results are compared with the classical Poisson-Boltzmann (PB) double layer theory developed for diluted electrolytes and applied to a cylindrical capillary of infinite extent. While the surface electrostatic potential was effectively screened by the counter ions inside the largest channels of 8.1 nm in diameter (SBA-15), the effect of the surface electrostatic potential on local effective pH was significant for the 3.2 nm channels (C 16 MCM-14). The smaller channels of C 12 MCM-41 (2.3 nm in diameter) provided the most critical test for the PB equation that is based on a continuum electrostatic model and demonstrated its inapplicability likely due to the discrete nature of molecular systems at the nanoscale and nanoconfinement effects, leading to larger spatial heterogeneity. © 2018 American Chemical Society. *E-mail: gek1969@bk.ru (E.G.K.). *E-mail: Alex_Smirnov@ncsu.edu (A.I.S.). ORCID Alex I. Smirnov: 0000-0002-0037-2555 Author Contributions The manuscript was written through contributions from all the authors. All authors have given approval to the final version of the manuscript. Funding E.G.K., L.S.M., D.O.A., D.P.T., and A.N.T. acknowledge the financial support of the Program 211 of the Government of the Russian Federation no. 02.A03.21.0006, RFBR grants 17-03-00641 and 18-29-12129mk, and the State Task from the Ministry of the Education and Science of the Russian Federation nos. 4.9514.2017/8.9 and 4.7772.2017/8.9. A.M. and A.I.S. acknowledge the financial support of the U.S. DOE Contract DE-FG02-02ER15354 (modeling of electrostatic phenomena in the nanochannels and the final preparation of the manuscript). Notes The authors declare no competing financial interest.

Novel 1,3-diphenyl-5-(benzothiazol-2-yl)-6-R-verdazyls, stable free radicals, were synthesized from the corresponding formazans by alkylation followed by cyclization and oxidation of the intermediate leucoverdazyls (yields 78–93%). The radicals were characterized by ESR, electronic and IR spectroscopy, mass spectrometry, X-ray diffraction (for one of them) and cyclic voltammetry. The resulting verdazyls are stable under ordinary conditions and are reduced more readily but more difficult to oxidize than the triphenylverdazyl analogue.

A brief list of the main directions in radiation technologies using ionizing radiation in a wide range of doses and energies is given. The necessity of dose control in irradiated objects and diagnostics of radiation fields is proven. It is noted that in world practice these problems are solved using an EPR dosimetry system using detectors based on L-α - alanine. A series of experimental results was obtained, showing the possibility of using Russian EPR / PTFE dosimetry system for routine dose measurements during radiation sterilization of medical equipment.

The electron paramagnetic resonance (EPR) spectra of the late 20th century was used to create a practical source for the detection of irradiated products. EPR spectrometry is suitable for dry products (cereals, spices) or food components that are relatively dry (i.e. shell, seeds, bones). The relative ease, with which radiation-induced EPR signals can be measured in meat, seafood, and fruits, has been demonstrated. The possibility of using EPR dosimetric control of chicken eggshells is of high relevance in connection with the use of radiation processing methods of these products and allows studying without the use of dosimeters. In this work, we conducted a study of EPR spectrometry after radiation treatment of chicken egg’s shells with a dose of 40 kGy. The results obtained will allow determining the method of chicken eggs control exposed to surface radiation treatment with a nanosecond electron beam (NEB).

Reaction of quinoxaline or its 6,7-difluoroderivative with C-nucleophiles in nitrogen atmosphere afforded along with the products of hydrogen substitution in the heterocyclic ring the corresponding bisquinoxalines. An ESR signal of the cation-radical of the diprotic salt of quinoxaline was detected in the DMSO solution of quinoxaline and dimedone.

The article describes diagnostics and surgical treatment of a rare benign tumor (lipoblastoma) of four anatomical areas of the head and neck in an 8-months child. Diagnostic data, surgical procedure performed using microsurgical techniques and intraoperative neuromonitoring and the patient's condition in the long-term postoperative period are presented. The histological conclusion about the removal of the tumor with negative resection margins suggests favorable prognosis of the disease.В настоящей работе описана диагностика и хирургическое лечение редкого доброкачественного новообразования — липобластомы — четырех анатомических областей головы и шеи у ребенка в возрасте 8 месяцев. Представлены данные диагностики, ход операции, выполненной с применением микрохирургической техники и интраоперационного нейромониторинга, а также состояние пациента в отдаленном послеоперационном периоде. Гистологическое заключение об удалении опухоли в пределах здоровых тканей позволяет говорить о благоприятном прогнозе основного заболевания.