Reactions of 1,3-dipolar cycloaddition are the focus of modern research due to the wide range of reagents and the simplicity of the reactions and, consequently, the great synthetic potential for both the development of fundamental chemical science and for the preparative and industrial production of practically significant compounds.

The [3+2]-cycloaddition of azomethinylides formed in situ to dipolarophiles is a promising method for the synthesis of dispyro derivatives of oxindole and acenaphthenedione. In the course of our studies, it was shown that the cycloaddition of azomethinylide occurs only through the exocyclic double C=C bond, which leads to the formation of a new pyrrolidine cycle as part of the molecule and, as a result, a dispyroheterocycle.

This work is devoted to the synthesis and study of the structure of 2-arylmethylidene derivatives and dispyrothiazolo[3,2-a]pyrimidine both in the solution and in the crystalline phase.

The unique property of supramolecular self-assembly of the condensation products of 2-arylmethylidenedithiazolo[3,2-a]pyrimidines with isatin and sarcosine is the formation of microporous material, which further allows the use of crystalline samples of these derivatives as potential absorbents.

Hence, the synthesis was successfully carried out and the structure of the obtained dispyrothiazolo[3,2-a]pyrimidine derivatives in the solution and in the solid phase was studied, and the possibility of creating microporous materials was discovered. The obtained derivatives were characterized by a complex of physico-chemical methods (IR, NMR-¹H and ¹³C spectroscopy, ESI-MS spectrometry, X-ray diffraction analysis).

Heterocyclic compounds of 1,3,4-thiadiazole are the important class of substances with a wide spectrum of biological activity.

In the conditions of experiment, was synthesed a new 1,3,4-thiadiazole derivative - 5,5'-(methylenebis(sulfanediyl))bis(3-phenyl-1,3,4-thiadiazole-2(3H)-thione) and was estimated the structural features of compound, as well as analysis of its potential biological activity.

The crystal structure of (methylenebis(sulfanediyl))bis(3-phenyl-1,3,4-thiadiazole-2(3H)-thione) has been determined by X-ray diffraction and intermolecular interactions have been analyzed by HS. Crystallographic data have been deposited with Cambridge Crystallographic Data Centre (Deposite Number 2255753).

The biological activity spectrum of 5,5'-(methylenebis(sulfanediyl))bis(3-phenyl-1,3,4-thiadiazole-2(3H)-thione) were studied by PASS Online software, and obtained data let to describe biological activity properties in a depending of its structure. According to the data of analysis, 5,5'-(methylenebis(sulfanediyl))bis(3-phenyl-1,3,4-thiadiazole-2(3H)-thione) was very likely to exhibit the activity of аmyloid beta precursor protein antagonist.

On the base of structural features of that compound, we suppose that on the molecular level, the 1,3,4-thiazole moieties of new derivative, will interact with protein’s cysteine ​​residues. Additionally, the presence of a disulfide bridge separated by a methylene fragment will facilitate easy penetration through the cell membrane, leading to subsequent exhibiting activity. Confirmation of the potential properties of the new compound and researching the interconnection between the structure of 1,3,4-thiadiazole derivative and its biological activity, as well as explanations of its action mechanism on the molecular level, are ongoing.

Quinoxazoline derivatives are renowned for their extensive pharmacological activities and substantial industrial importance. Recognizing their multifaceted applications, this study aims to synthesize novel quinoxazoline derivatives, specifically 2-Aryl-3-(2’-n-butyl-4’-chloro-1’-H-imidazol-5’-yl)-quinoxazolines, and investigate their antimicrobial properties. The synthesis process involved the condensation of a precursor molecule (Type II) with bromine (Br₂) in acetic acid (HAc) and 1,2-diaminobenzene, resulting in the formation of the desired quinoxazoline derivatives (Type III).

The structural elucidation of the synthesized compounds was carried out using a combination of spectroscopic techniques, including Nuclear Magnetic Resonance (NMR), Infrared (IR) spectroscopy, and Mass Spectrometry (MS), which confirmed the successful formation of the targeted molecules. The antimicrobial efficacy of these new derivatives was evaluated through a series of bioassays against a diverse panel of bacterial and fungal strains.

Preliminary results indicate that these quinoxazoline derivatives exhibit significant antimicrobial activity, demonstrating potential as effective agents in combating microbial infections. This research expands the library of quinoxazoline-based compounds and highlights their possible application in developing new antimicrobial therapies.

The findings underscore the versatility and importance of quinoxazoline derivatives in medicinal chemistry, offering insights into their broader applications. This study lays the groundwork for further exploration and optimization of quinoxazoline-based molecules, aiming to enhance their efficacy and broaden their industrial and pharmaceutical applications.

The chemistry of heterocyclic compounds is one of the leading areas of organic chemistry. These compounds can serve as the basis for both natural biologically active substances and synthetic ones. In recent years, an interest to the thiazolopyrimidines increased because of their different biological properties that can be used in medicine.

Also, modification of the thiazolopyrimidine platform using various pharmacophore groups such as arylmethylidene and arylhydrazone which have a variety of medicinal properties may become the basis for the design of new generation drugs.

The further functionalization of both arylmethylidene and arylhydrazone derivatives was investigated by our scientific group and two new rearrangements in the thiazolo[3,2-a]pyrimidine derivatives series were opened.

It was established that 2-arylhydrazone derivatives of thiazolo[3,2-a]pyrimidine under microwave activation conditions in a mixture of methanol and pyridine undergo rearrangement into [1,2,4]triazolo[4,3-a]pyrimidines.

The rearrangement of arylmethylidene thiazolo[3,2-a]pyrimidine to imidazo[2,1-b]thiazole under the reaction with NBS in an acetone-water mixture in the presence of ammonium acetate at room temperature was also revealed. Apparently, initially formed by the endocyclic double C=C bond of the thiazolopyrimidine platform bromohydrin rapidly goes through transformation into an unstable oxyrane, which then launches this rearrangement.

The obtained derivatives were characterized by a complex of physico-chemical methods (IR, NMR-¹H and ¹³C spectroscopy, ESI-MS spectrometry, including single-crystal X-ray diffraction analysis).

Hydrazones are a broad class of organic compounds, and due to their high reactivity they can act as intermediates in organic synthesis or be used as independent substances in various fields of science and technology. Despite significant research in the field of hydrazone chemistry, we noticed that there is no information in the literature on the synthesis of hydrazones of various strained polycyclic hydrocarbons.

In this work, for the first time, the synthesis of unsubstituted hydrazones was carried out based on various strained polycyclic hydrocarbons, which are of interest as promising building blocks in organic chemistry and medicine. Polycyclic hydrocarbons result from the dimerization of norbornadiene with a wide range of unsaturated compounds under Diels-Alder reaction conditions. There are a larger number of norbornadiene dimers, so we chose three compounds as objects of study as the most frequently formed and with good yields under dimerization reaction conditions, namely exo-exo-4-exo-Acetoxypentacyclo[8.2.1.1^5,8.0^2,9.0^3,7] tetradecane, endo-endo-4-exo-Acetoxypentacyclo[8.2.1.1^5,8.0^2,9.0^3,7] tetradecane and Acetoxyhexacyclo[9.2.1.0^2,7.0^3,5.0^4,8.0^9,13]tetradecane. The synthesis of hydrazones includes several successive stages, according to which at the first stage acetates are formed by boiling in acetic acid of the starting polycyclic hydrocarbons. The second stage involves the saponification of esters to the corresponding alcohols under the action of an alcoholic solution of potassium hydroxide. The third and fourth stages involve the subsequent oxidation of alcohols and the introduction of a new functional group using excess hydrazine hydrate. As a result, the corresponding unsubstituted hydrazones from strained polycyclic hydrocarbons were obtained. The yield of final products was 85-90%.

One of the most interesting classes of organic photochromic compounds capable of reversible isomerization under the influence of external stimuli are spiropyrans.

The optical and other physicochemical properties of the isomeric forms of spiropyrans differ significantly from each other, which makes it possible to use these photochromes as sensors, optoelectronic and holographic devices, memory elements, etc. Also, an undoubted advantage of spiropyrans compared to other classes of photochromic compounds is the relative ease of their preparation and structural modification. At the same time, modification of the structure of spiropyrans by introducing various functional groups opens up great synthetic possibilities for the targeted synthesis of new photochromes with a wide variation of their spectral and kinetic properties.

In development of research aimed at expanding the boundaries of the use of spirophotochromic compounds, in order to obtain new light-controlled materials with different characteristics, as well as to study the influence of functional groups in the spirophotochromic molecule on the spectral and photochromic properties, we have synthesized a new spiropyran.

In this work, we synthesized a new salt of photochromic spiropyran containing various functional groups (-CHO, -NO₂, -OCH₃, -(CH₂)₅N(CH₃)₂*HBr), capable of reversibly responding to external influences. Photoinduced transformations, spectral and kinetic characteristics of the synthesized compound were studied.

Bistable compounds capable of reversible molecular rearrangements between two nonequivalent states are of great interest for the creation of new materials and the study of many chemical and biological processes that are used in modern technologies. One of the most studied mechanisms of the functioning of such bistable systems is photochromism - a change in the structure and spectral properties of compounds under the influence of external factors. Among the most studied classes of organic photochromic structures are spirocyclic compounds, such as spiropyrans, which are capable of switching between the usually colorless cyclic and colored merocyanine forms when exposed to external stimuli such as light, temperature, pressure, polarity, mechanical stress, electric or magnetic field, which allows their use in memory elements, as optoelectronic devices, sensors, etc.

The choice of spiropyrans as model compounds of this class of photochromic molecules is not accidental, since they are the most well-known and unique representatives of photochromic compounds due to the relative ease of their preparation, structural modification and the possibility of targeted changes in spectral and kinetic characteristics over a wide range. The isomeric forms of spiropyrans differ significantly in their physical and optical properties, which makes them very promising compounds for use in various fields of science and technology.

In this work, we report the synthesis of a new salt of photochromic spiropyran containing various functional groups (-CHO, -NO₂, -OCH₃, -(CH₂)₅PPh₃), capable of reversibly responding to external influences. Photoinduced transformations, spectral and kinetic characteristics of the synthesized compound were studied.

Introduction

(Het)arylmethylidene derivatives of furan-2(3H)-ones rightfully occupy a special place in modern organic chemistry, since they are present in various natural compounds and also provide building blocks in the synthesis of various potential biologically active compounds. From this point of view, hybrid systems containing furan-2(3H)-one and chromen-4(4H)-one fragments are promising for research, modification of which will further expand the spectrum of biological activity of new hybrid structures

Experimental details

3-((5-(2-hydroxyphenyl)-1H-pyrazol-4-yl)methylene)-5-arylfuran-2(3H)-ones were synthesized by the reaction (E)-3-((2-oxo-5-arylfuran-3(2H)-ylidene)methyl)-4H-chromen-4-ones with excess hydrazine monohydrate in ethyl alcohol in good yields. The composition and structure of all compounds were characterized by a complex of spectroscopic methods (IR, NMR).

Results and Discussion

Taking into account the structure of the reaction products, it can be assumed that an attack of hydrazine occurs at the C₂-O bond of the chromen-4-one fragment, accompanied by ring opening with the formation of an enamine fragment; further attack of the amino group at the C=O group of the original chromen-4-one leads to the formation of a pyrazole cycle in the final reaction products.

Acknowledgments

This work received financial support from the Foundation for Assistance to Small Innovative Enterprises (FASIE) (grant no. 18695GU/2023 to Arzyamova E.M.).

Substituted 2H-pyran-2-ones are systems with a wide spectrum of pharmacological activity, therefore they are used as a substance in many modern drugs, which determines the relevance of creating complex systems based on them, including polycyclic O-, S-heterosystems. In recent years, Lawesson's reagent has been explored for the synthesis of both open-chain P,S-containing derivatives and P,S-heterocyclic systems, with potential biological activity.The character of the interaction between arylmethylene-2H-pyran-2-ones and Lawesson's reagent depends on the structure and position of the substituent in the aromatic ring of the substrate and on the polarity of the reaction medium. Three main pathways were shown to be realized for this group of compounds. In the absence of a substituent in the ring, the reaction proceeds as a classical thionation followed by S-heterocyclization. In the presence of the most electron-withdrawing nitro group at the metaposition of the substituent, the enol form of the substrate is stabilized, which promotes the formation of a new pyran ring. For the substrate with a chlorine atom at the paraposition of the cycle, according to the result of the decomposition of UV spectra by the chemometric method of independent components (MILCA) of the benzannulated analog, the content of the keto tautomeric form in nonpolar solvents is higher compared to that for the meta-NO₂ group, which explains the presence of both O- and S-heterocyclization products in the reaction mixture.

The [6+2] cycloaddition of (2-butyl-2,3-butadienyl)(trimethyl)silane and 2,3-butadienyl(trimethyl)silane to 1,3,5-cycloheptatriene was studied using titanium- and cobalt-containing multicomponent catalytic systems: R2TiCl2-R'nAlCl3-n (R = acac, PriO, ButO, Cl; R' = Et, Bu, n = 2, 3) and CoX2(Y)/Z/ZnI2 (X = acac, Br, I , Cl, OAc; Y = dppe, dppm, dppp, dppb, Ph3P, P(OPri)3, P(OPh)3; Z = Zn, Mg, In, Bu4NBH4). The work investigated the influence of the nature of the central atom of the catalyst, the ligand environment of the catalyst, the nature of the organoaluminum cocatalyst, the reducing agent, the effect of temperature, as well as the nature of the solvent on the yield and stereoselectivity of the formation of cycloadducts. Catalytic cyclocodimerization occurs with the formation of silicon-containing bicyclo[4.2.1]nona-2,4-dienes, which are of interest as promising precursor compounds in the synthesis of new drugs. It is known that many bridged carbo- and heterocarbocyclic compounds containing silicon atoms in the structure have diverse biological activities and are valuable drugs. Based on this, the work for the first time carried out a comprehensive study of the antitumor activity of synthesized silicon-containing bicyclo[4.2.1]nona-2,4-dienes in vitro using various tumor cell lines (U937, K562, Jurkat, HL60) and normal fibroblasts.