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Enteroviruses are non-enveloped viruses of Enterovirus genus, Picornaviridae family, causing a variety of human diseases: from acute respiratory and intestinal infections to more severe pathologies including poliomyelitis, encephalitis, myocarditis, pancreatitis. Currently, no approved direct-acting antiviral drugs for treatment of enterovirus infections exists, whereas vaccination is available only for prevention of poliomyelitis and enterovirus 71 infection. Therefore, it is promising to conduct a search for inhibitors of enteroviruses life cycle in drug development to treat enterovirus infections. Here, antiviral properties of stable free radicals, verdazyls, and their precursors, leucoverdazyls, were investigated. It has been shown that leucoverdazyls vs verdazyls increased the survival of permissive cell culture infected with coxsackievirus. The activity range of the lead leucoverdazyl against RNA-containing and DNA-containing human viruses (in the viral yield reduction assay) and its proposed mechanism of action (time of addition assay) was studied. The lead compound suppressed reproduction of group B enteroviruses in vitro, with modest activity against influenza A virus and no activity against herpes virus type 1 and adenovirus type 5. The maximum decrease in viral titers was observed upon its addition to infected cells during early and middle stages of the virus life cycle. Thus, we concluded that the studied compound has a pronounced inhibitory activity against group B enteroviruses not belonging to the class of capsid binder inhibitors, without virucidal properties. Previously, we described antioxidant properties of leucoverdazyls. It is known that many viral infections are accompanied by production of reactive oxygen species and oxidative stress, and some compounds with antioxidant properties exhibit antiviral potential. Targeted chemical modifications of leucoverdazyls and further studies of leucoverdazyl mechanism of action as well as in vivo animal studies are needed. However, the results obtained may be useful for future development of new antiviral drugs to treat enteroviral infections.

Synthetic approaches for 2,4,6-trisubstituted-1,3,5-triazine systems are analyzed, and their properties attractive to practical applications in fluorescent materials are reviewed.

A number of new 4-anilinoquinazolines were synthesized starting from 6,7,8-trifluoro-2-(methyl­sulfanyl)quinazolin-4(3H)-one. Reactions of the title compounds with cyclic secondary amines involved substitu­tion of the 7-fluorine atom with retention of the methylsulfanyl group on C2. 6,7,8-Trifluoro-4-(2-me­thoxyanilno)-2-(methylsulfanyl)quinazoline showed in vitro tuberculostatic activity with a minimum inhibitory concentration of 1.5 μg/mL.

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.

A series of 4,5-diphenyl-7H-thieno[2′,3′:3,4]pyrido[2,1-b]quinazolin-7-ones was synthesized via the Rh(III)-catalyzed annulation of 2-thienylquinazolin-4(3H)-ones with diphenylacetylene. 2-Phenylquinazolin-4(3H)-one amide alcoholysis and double C–H functionalization proceeded under the same reaction conditions with the formation of 2,3,7,8-tetraphenyl-1H-benzo[d,e][1,8]-naphthyridine derivatives. All compounds possess fluorescence properties in MeCN and toluene solutions as well as in the solid state. The aggregation induced emission (AIE) properties and the ability to detect Fe3+ cations were evaluated.

Extensive research on the synthesis and application of tetrazine derivatives for electronic devices, luminescent elements, photoelectric conversion elements, and image sensors has been published recently. This review covers reported data on the modern trends in the design of functionalized tetrazines obtained within the period 2010–2020. Aryl(heteroaryl) and arylvinyl derivatives of tetrazines and their photoluminescence and application for fluorogenic probes are discussed. Examples of photosensitive oligomers and polymer 3,6-dithienyltetrazines are reviewed.

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.

New 2,5-bis(azacyclohex-1-yl)-8-nitro-1,3-benzothiazin-4-ones were synthesized from 2,6-difluorobenzoic acid in two preparative stages. The ethoxycarbonylpiperazino derivative surpasses in tuberculostatic activity (MIC 4 μg ml−1) its 5-fluoro-8-H-counterpart. The first representative of 5-fluoro-8-nitro-1,3-benzothiazin-4-ones was obtained through the condensation of 2,6-difluoro-3-nitrobenzoyl isothiocyanate and N-methylindole.

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 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.

Synthesis, structure, properties, and reactivity of verdazyls based on formazans, as well as of metalverdazyl complexes, formazanate BR2-complexes (R = F, H, Ph), and other Group 13 and 14 formazanate complexes, were considered. Special attention was focused on the study of redox-active formazanate ligands.

In this study we present a synthesis of six-membered BF2complexes with N–B–O type linkage based on 2-(2-hydroxyphenyl)-4-phenylquinazolines and 2-(2-hydroxyphenyl)quinoxaline. The photophysical properties of compounds were studied by absorption and fluorescence spectroscopy and compared with parameters of earlier developed 2-(2-hydroxyphenyl)-3H-quinazolin-4-ones analogues. Some difluoroboron complexes were found to be highly emissive in the solid state. The nature of benzazine core as well as intermolecular interactions proved to have a significant influence on photophysical properties.

Currently, the chemistry of organofluorine compounds is a leading and rapidly developing area of organic chemistry. Fluorine present in a molecule largely determines its specific chemical and biological properties. This thematic issue covers the trends of organofluorine chemistry that have been actively developed in Russia the last 15 – 20 years. The review describes nucleophilic substitution and heterocyclization reactions involving fluorinated arenes and quinones and skeletal cationoid rearrangements in the polyfluoroarene series. The transformations involving CF3-substituted carbocations and radical cations are considered. Heterocyclization and oxidative addition reactions of trifluoroacetamide derivatives and transformations of the organic moiety in polyfluorinated organoboranes and borates with retention of the carbon – boron bond are discussed. Particular attention is devoted to catalytic olefination using freons as an efficient synthetic route to fluorinated compounds. The application of unsymmetrical fluorine-containing N-heterocyclic carbene ligands as catalysts for olefin metathesis is demonstrated. A variety of classes of organofluorine compounds are considered, in particular, polyfluorinated arenes and 1,2-diaminobenzenes, 1-halo-2-trifluoroacetylacetylenes, α-fluoronitro compounds, fluorinated heterocycles, 2-hydrazinylidene-1,3-dicarbonyl derivatives, imines and silanes. The potential practical applications of organofluorine compounds in fundamental organic chemistry, materials science and biomedicine are outlined. The bibliography includes 1019 references.

Novel fluorinated 2-substituted 1,3-benzothiazin-4-ones were obtained through the addition of N-nucleophiles to ortho-fluorobenzoylisothiocyanates, followed by cyclization of fluorobenzoyl-thioureas. Synthetic approaches to original 2-cycloalkylimino- and 2-carbonylpiperazino- substituted benzothiazinones, bearing different number of fluorine atoms in the benzene ring have been found. 2-Ethoxycarbonylpiperazino-5-fluoro-1,3-benzothiazin-4-one proved to exhibit a high tuberculostatic activity in vitro (MIC 0.7 microgram/mL), thus indicating that a search of biologically active compounds in this family of heterocycles appears to be a reasonable approach.

New 2-(1-methyl-1H-pyrrol-2-yl)- and 2-(1-methyl-1H-indol-3-yl)-5-fluoro- and -6,7,8-trifluoro-1,3-benzothiazin-4-ones have been synthesized in high yields by reaction of o-fluorobenzoyl isothiocyanates with C-nucleophilic 1-methyl-1H-pyrrole and 1-methyl-1H-indole, followed by base-catalyzed cyclization. The products were characterized by 1H, 13C, and 19F NMR and mass spectra and X-ray diffraction data.

Background: Quinazolines, the important group of benzodiazines, are widely known in medicinal chemistry due to their broad spectrum of biological activities. Notably, extensive research on the synthesis and application of quinazoline derivatives for electronic devices, luminescent elements, photoelectric conversion elements, and image sensors has been published recently. Objective: This review reports luminescent small molecules and chelate compounds including a quinazoline or pyrimidine ring in their scaffold highlighting their applications related to photo- and electroluminescence. Conclusion: It is clear from the review of the topic that the incorporation of quinazoline and pyrimidine fragments into π-extended conjugated systems is of great value for the creation of novel optoelectronic materials. Polyhalogen derivatives represent the major starting materials for polysubstituted fluorescent quinazolines. Electroluminescent properties of aryl(hetaryl)substituted quinazolines with π-extended conjugated systems proved to be the most important. Incorporation of benzimidazole, carbazole, triphenylene or triphenylamine fragments into quinazoline scaffold allows fabricating materials for organic light-emitting diodes, including white OLEDs and highly efficient red phosphorescent organic light-emitting diodes. Moreover, arylvinylsubstituted quinazolines are of great interest as potential structures for nonlinear optical materials and for colorimetric pH sensors. Iridium complexes based on 2-aryl(thienyl) quinazoline or pyrimidine derivatives represent high-efficiency phosphorescent materials for OLEDs. Pyrimidine push-pull systems are of considerable importance as potential photosensitizers for dye-sensitized solar cells. Pyrimidine derivatives bearing phenylacridine or phenylphenoxazine fragments at the positions 4 and 6 are capable to function as thermally activated delayed fluorescence emitters.

In the frames of this review article the recently obtained data on new synthetic approaches to fluorinated indoles, as well as their biological properties are considered.

International audience; A series of chromophores bearing 4-cyanoquinazoline, 2-(4-cyanophenyl)quinazoline or 2-(4-trifluorophenyl)quinazoline electron-acceptor (A) and 5-(4-aminophenyl)thiophen-2-yl or 4-aminophenyl electron-donor (D) units has been designed. The influence of the electron-withdrawing substituent on the pyrimidine core as well as the nature of the amino electron donating group has been studied by cyclic voltammetry, UV/Vis and emission spectroscopy. Whereas 2-(4-cyanophenyl)quinazoline and 2-(4-trifluorophenyl)quinazoline derivatives are highly luminescent in chloroform solution, 4-cyanoquinazolines are poorly emissive. Interestingly all compounds are luminescent in the solid state with the emission ranging from blue to red. The second order nonlinear optical properties were studied using electric field induced second harmonic generation (EFISH) method. Quantum-chemical calculations corroborate the aforementioned experimental results.

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.

Extensive research on the synthesis and application of benzazine derivatives for electronic devices, luminescent elements, photoelectric conversion elements, and image sensors has been published recently. This review covers article data obtained within the period 2012 – 2018 on the synthesis and optical properties of functionalized quinolines, quinoxalines and quinazolines. Arylvinyl, arylethynyl and (het)aryl derivatives of these benzazines, their photoluminescence and photoisomerization are discussed. Examples of photosensitive annelated, oligo- and polymeric benzazines and also coordination compounds with benzazine ligands are reviewed. The bibliography includes 267 references.

2-(2-Hydroxyphenyl)–3H-quinazolin-4-ones with diverse substituents at phenol ring and their six-membered difluoroboron complexes have been synthesized via few-stage approach. The photophysical properties of target compounds have been investigated in two solvents as well as in the solid state. The nature of substituents and substitution point in the phenol moiety of ligands and resulting BF2-complexes on the photophysical properties of dyes have been explored. The complex bearing two t-Bu groups proved to be the most emissive in solid state, whereas its 5-methoxy and 4-diethylamino counterparts possess strong emission in toluene solution. The dyes exhibited large Stokes shifts which was attributed to excited state intramolecular proton transfer (ESIPT). Additionally, fluorescence of quinazolinones in the mixture of THF/water was studied. All ligands demonstrated emission enhancement with increase of water fraction which was due to aggregation induced emission.

New synthetic approaches to fluorinated indazoles, as well as the features of their biological properties are presented and discussed in the frames of this review article.

This review is focused on consideration of effects of the nature of N,N’- and N,O-bidentate ligands on the structure and optical properties of their B(III) complexes. It has been established that B...

The synthesis of novel push–pull 2,4-disubstituted quinazolines was performed by the bromodeoxygenation of 2-phenyl-, 2-(fluoren-2-yl)- and 2-cymantrenylquinazolin-4-ones and subsequent palladium-catalyzed Suzuki reactions. According to the optical studies, derivatives containing 4-positioned 4-diethylaminophenyl substituent exhibit higher luminescence in toluene solutions as compared to acetonitrile ones.

Novel N,O-bidentate BF2 and BPh2 complexes have been prepared in good to excellent yields through coordination of 8-hydroxy-2-methylquinolines and 2-(2-hydroxyphenyl)-3Н-quinazolin-4-ones with boron trifluoride etherate or triphenylborane under mild conditions. All complexes have been characterized by 1H, 11B and 19F NMR, mass-spectrometry and X-ray crystallography data. Some complexes have been found to exhibit a significant fluorescence in acetonitrile solutions. Electronic and site effects of substituents in both heterocyclic and phenol fragments proved to have a profound impact on quantum yields.

In the frames of this review article the recently obtained data on new synthetic approaches to fluorinated pyrazoles and their condensed analogs, as well as their biological activities have been analyzed.

The effect of fluorine atoms in the benzene ring on the photophysical properties of 2-methyl-6,7-difluoro-8-hydroxyquinoline is studied.

Tuberculosis (TB) takes the second place among the reasons for mortality from infectious diseases. For this reason, the problem of tuberculosis treatment requires urgent attention all over the world. Some 2-amino substituted 1,3-benzothiazin-4-ones (2-amino-1,3-BTZs) represent a promising new class of antitubercular agents. Other 1,3-benzothiazin-4-one derivatives, mostly 2-aryl and 2- (pyridin-2-yl) ones, are attractive due to their ability to suppress oxidative stress-induced cardiomyocyte apoptosis. This review covers the synthetic approaches to 2-amino- and 2-aryl(heteryl) substituted 1,3-benzothiazin-4-ones (1,3-BTZs). A brief overview of structure-activity relationships is presented.

This review is focused on consideration of the influence of ligands and synthetic conditions on the structure and optical properties of a variety of metal complexes based on derivatives of quinoline, quinoxaline, and quinazoline. It has been established that changing of substituents in a given ligand provides an opportunity to tune color and intensity of the photoluminescence of the corresponding Al(III) and Zn(II) complexes, while variation of auxiliary ligands in cyclometalated complexes leads to emission emergence at ambient temperature. Difluoroboron complexes of metals with N,O-bidentate ligands proved to exhibit a strong photoluminescence in both solutions and the solid state. Some complexes of this type are useful for electroluminescent or solar cell devices. Biological activity of quinoline complexes is governed mainly by the metal nature.

Novel Zn(II) complexes with 2-styryl-8-hydroxyquinoline were synthesized and characterized by 1H, 19F, and 13C NMR spectroscopy and X-ray diffraction analysis. Photoluminescence properties of the ligands and complexes in solutions were studied. The effect of substituents in the quinoline and phenylethenyl fragments on spectral characteristics was discussed.

Published data from 1992-2013 on methods for the synthesis and biological activity of fluorine-containing benzimidazoles and their [a]- and [b]heteroannelated derivatives are summarized and classified.

Novel ligands were synthesized by the reaction of benzazine-2-carbaldehydes or methyl pyrazinyl ketone with benzhydrazide, as well as their ZnII and CdII complexes with the N,N,O environment. Their structures and photophysical properties were studied. The synthesized complexes are photoluminescent.

Published data on methods of synthesis, chemical properties, and biological activity of fluoroimidazoles and their heteroannelated derivatives are summarized and classified.

Synthesis, structure, properties and reactivity of stable heterocyclic radicals, verdazyls, are considered. Special attention is focused on metal verdazyl complexes. Major areas of application of such radicals are discussed. The bibliography includes 164 references.

The synthesis and X-ray diffraction study of 1-benzyl-2-[2-(5- ethyltetrazole-2-yl)-phenoxy]-1H-benzimidazole and 1-benzyl-2-[2-(5- ethyltetrazole-2-yl)-4-nitrophenoxy]-1H-benzimidazole single crystals have been performed. The oxidative splitting of an azo-hydrazone group of 1-(2-hydroxy-(5-nitro)phenyl)-3-ethyl-5-(benzylbenzimidazolyl)formazans, a break in the C2-N1 bond, the interaction of o-hydroxyl group of aryl fragment with oxygen, and the formation of new 2-(phenoxy)benzimidazoles are found to occur in the presence of perchlorate iron(III). © 2013 Pleiades Publishing, Ltd. This study was supported by the Russian Foundation for Basic Research, project nos. 11 03 90724 mob_st and 11 03 00181a.

Novel 3-phenyl/pyridinyl-trans-2-(aryl/heteryl)vinyl-3H-quinazolin-4-ones 3a,b, 4a, 5a, 7a and their 6,7-difluoro de- rivatives 3c,d, 4b, 5b, 7b have been obtained by condensation of the correspondent 2-methylquinazolin-4-ones 1, 6 with aromatic (heterocyclic) aldehydes in the presence of ZnCl2 (AcONa) or by the reaction of 2-methyl-3,1-benzoxazin-4- ones 2 with the Shiff bases. Effects of aryl(heteryl) substituents on photophysical properties of (aryl/heteryl) quinazolinylethenes have been studied.

Methods for the synthesis of styrylazines and styrylbenzazines are considered, their photophysical and photochemical properties are analyzed. The review covers both published data and own works of the authors. Important data on the prospects of application of arylhetarylethenes as components of electroluminescence materials are discussed. The bibliography includes 124 references.

N-(2-Phenylquinazolin-4-yl)-N′-salicylidenehydrazines and their ZnII complexes were obtained. The structures and luminescent properties of these new quinazoline derivatives were examined.