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A series of promising luminescent materials, nonlinear optical crystals, and physiologically active compounds - aryl(oxy)(sulfanyl)(sulfonyl)acetates of guanidine (A) of unknown type was synthesized. Various functional groups present in (A) were identified using FTIR spectroscopy. 1 H and 13 C NMR spectral studies further confirm the molecular structure (A). Crystals of guanidinium 4-chlorophenyl(sulfanyl)acetate (1) and guanidinium 4-chlorophenyl(sulfonyl)acetate (2) were successfully grown. They belong to the same lowest symmetry category, but to different crystal systems: monoclinic (1) and orthorhombic (2). It has been established that intrinsic optical absorption begins at a wavelength of ∼ 290 nm for crystalline compound (1) and ∼ 335 nm for crystal (2). The intrinsic luminescence spectrum of crystal (1) includes two bands with maxima at 300 and 515 nm. In the intrinsic luminescence spectrum of crystal (2), only one band is observed with a maximum at 350 nm. Such luminescence in both crystals is excited in the intrinsic absorption bands, as well as by X-ray radiation. In addition, in the near ultraviolet and throughout the visible region, where optical absorption is not detected (it is very weak), low-inertia (less than 10 ns) rather intense luminescence of uncontrolled impurity-defect centers is excited. The spectral bands of optical absorption, photo- and X-ray luminescence discovered in experiments were systematized using a diagram of energy levels and quantum transitions in crystals and defect centers of the compounds under study., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A previously unknown class of fluorophores was discovered, which represents 14-membered bridgehead heterocycles, pyrrolyl-diazabicyclo[8.3.1]tetradecadienones, herein referred to as PY-14-ONEs. The new fluorophores are characterized by giant Stokes shifts of ∼8000-10,250 cm -1 and virtually zero overlap of the absorption and emission bands. They exhibit fluorescence maxima in the blue-green region (454 ≤ λ em ≤ 513 nm, MeCN), which shift to the red side when converted to their water-soluble salts by alkylation with MeI (478 ≤ λ em ≤ 516 nm, water). PY-14-ONEs were obtained by an original synthesis from DBU, 1,8-diazabicyclo[5.4.0]undec-7-ene, which reacts with acylethynylpyrroles without catalysts under mild conditions to afford PY-14-ONEs in a 34-58% yield. The reaction represents a ring expansion of DBU. Since acylethynylpyrroles are readily available, the discovered reaction opens promising possibilities for the development of new fluorophores. The results of our time-dependent DFT calculations indicate that the pyrrole ring in PY-14-ONEs plays an important role in the formation of the Stokes shifts, which can be further enhanced by attaching appropriate substituents to it, capable of creating in S 1 an extended conjugated system and causing a substantial alternation of the molecular structure via its planarization.

Nonsymmetric diarylethenes with an additional "stiff" cyclohexenol ring undergo various types of tandem transformations launched by light-induced 6π-photocyclization. Among these, there are two novel reactions (formal [1,3]-H migration and complete aromatization to an anthracene derivative) as well as photorearrangement and formal methane elimination. This diverse reactivity demonstrates the great potential of semi - stiff -diarylethenes in synthetic photochemistry.

Di(het)aryldiynes smoothly react with N -benzylaldimines in a [4 + 3] cycloaddition manner under the action of the KOBu t /DMSO system (60 °C, 30 min) to afford pharmaceutically relevant tetra(het)arylsubstituted 3 H -azepines in up to 71% yield. The process involves the addition of azaallyl anions to one of the triple bonds of diynes followed by prototropic isomerization and cyclization of anionic intermediates with participation of the second triple bond. The cascade mechanism is consistent with quantum-chemical analysis (B2PLYP-D3/6-311+G**//B3LYP-D3/6-31+G* + PCM).

An efficient method for the synthesis of pharmaceutically prospective but still rare functionalized 2,3'-bipyrroles (in up to 80% yield) by the cycloaddition of easily available acylethynylpyrroles with tosylmethylisocyanide (TosMIC) has been developed. The reaction proceeds under reflux (1 h) in the KOH/THF system. In the t -BuONa/THF system, TosMIC acts in two directions: along with 2,3'-bipyrroles, the unexpected formation of pyrrolo[1,2- c ]imidazoles is also observed (products ratio~1:1).

Coupling of photoswitching with dynamic covalent chemistry enables control of the formation and cleavage of covalent bonds by light irradiation. peri -Aryloxyanthraquinones feature an exclusive ability to switch electrophilicity by interconversion between para - and ana -quinone isomers, which was used for the first time for the implementation of a dynamic C-O bond. Photogenerated ana -isomers undergo a concerted oxa -Michael addition of phenols to give hitherto unknown 4-hydroxy-10,10-diaryloxyanthracen-9-ones. These species were found to be in equilibrium with the corresponding ana -quinones, thus forming a dynamic covalent system of a new type. Withdrawal of the colored ana -quinones from the equilibria by visible light irradiation resulted in two para -quinones with "locked" aryloxy groups.

A one-pot highly selective approach to the synthesis of hitherto unknown tetrahydropyrrolo[2',1':3,4]pyrazino[1,2- b ]pyrrolo[2',1':3,4]pyrazino[1,2- e ][1,2,4,5]tetrazine ensembles from simple and available N -allenylpyrrole-2-carbaldehydes and hydrazines has been developed. The reaction proceeds in a very facile manner and tolerates different substituents in both pyrroles and hydrazines. The novel class of organic compounds, tetrahydrodipyrrolodipyrazinotetrazines, proves to be promising pH-sensitive switchers to deliver N -aminopyrrolopyrazinium salts in acidic media and then again tetrahydrodipyrrolodipyrazinotetrazines in basic media. Both transformations give the products in quantitative yields.

We have discovered that three molecules of arylacetylene are rapidly (15 min) assembled with one molecule of nitrile at room temperature in the KOBu t /DMSO system to afford 2-aryl-3-arylethynyl-4-aryl-5-benzyl-1 H -pyrroles in up to 76% yield. We assume that this unprecedented self-organization process involves the cascade addition of acetylenic carbanions, first to the CN, then to the CC and CC bonds of the intermediates, followed by pyrrole ring closure via the intramolecular nucleophilic addition of the NH functional group to the CC bond of the final intermediates.

The aza-Michael reaction of 3-aminopropyltriethoxysilane ( 1 ) and -silatrane ( 2 ) with acrylates affords functionalized silyl-( 3 - 8 ) and silatranyl-( 9 - 14 ) mono- and diadducts with up to a 99% yield. Their structure has been proved with IR and NMR spectroscopies, mass spectrometry and XRD analysis. The hydrolytic homo-condensation of triethoxysilanes 3 - 5 gives siloxanes 3a - 5a , which form complexes with Ag, Cu, and Ni salts. They are also able to adsorb these metals from solutions. The hetero-condensation reaction of silanes 4 - 8 with OH groups of zeolite ( Z ), silica gel ( S ) and glass ( G ) delivers the modified materials ( Z4 , S7 , G4 , G5 , G7 , G8 , etc.), which can adsorb ions of noble metal (Au, Rh, Pd: G4 + Au , G5 + Pd , G7 + Rh ). Thus, the synthesized Si-organic polymers and materials turned out to be promising sorbents (enterosorbents) of noble, heavy, toxic metal ions and can be applied in industry, environment, and medicine.

There is incessant interest in the transfer of common chemical processes from organic solvents to water, which is vital for the development of bioinspired and green chemical technologies. Diarylethenes feature a rich photochemistry, including both irreversible and reversible reactions that are in demand in organic synthesis, materials chemistry, and photopharmacology. Herein, we introduce the first versatile class of diarylethenes, namely, potassium 2,3-diarylmaleates (DAMs), that show excellent solubility in water. DAMs obtained from highly available precursors feature a full spectrum of photoactivity in water and undergo irreversible reactions (oxidative cyclization or rearrangement) or reversible photocyclization (switching), depending on their structure. This finding paves a way towards wider application of diarylethenes in photopharmacology and bioinspired technologies that require aqueous media for photochemical reactions., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The biologically active compound 3-aminopropylsilatrane (a compound with a pentacoordinated silicon atom) underwent an aza-Michael reaction with various acrylates and other Michael acceptors. Depending on the molar ratio, the reaction yielded Michael mono- or diadducts (11 examples) containing functional groups (silatranyl, carbonyl, nitrile, amino, etc.). These compounds were characterized via IR and NMR spectroscopy, mass spectrometry, X-ray diffraction, and elemental analysis. Calculations (using in silico, PASS, and SwissADMET online software) revealed that the functionalized (hybrid) silatranes were bioavailable, druglike compounds that exhibited pronounced antineoplastic and macrophage-colony-stimulating activity. The in vitro effect of silatranes on the growth of pathogenic bacteria ( Listeria , Staphylococcus , and Yersinia ) was studied. It was found that the synthesized compounds exerted inhibitory and stimulating effects in high and low concentrations, respectively.

By using a quantum-chemical approach, B2PLYP-D2/6-311+G**//B3LYP/6-31+G*, we have carried out a detailed study of the assembly of 1-pyrrolines from N -benzyl-1-phenylmethanimine and phenylacetylene in the superbasic medium KO t Bu/dimethyl sulfoxide (DMSO). In this way, we have considered, both theoretically and experimentally, the mechanisms of the assembly through a concerted and stepwise nucleophilic cycloaddition and have addressed the side processes accompanying the assembly. It is found that the assembly via the concerted cycloaddition is kinetically more favorable than that via the stepwise cycloaddition. At the same time, the reaction of C-vinylation of aldimine with phenylacetylene occurs with a similar activation energy as the concerted cycloaddition and leads to the formation of 2-aza-1,4-pentadiene. The anion of 2-aza-1,4-pentadiene is an intermediate for the side processes leading to the formation of triarylpyridines and 1,3-diarylpropan-1-ones. Triarylpyridines are formed through the concerted cycloaddition of the next phenylacetylene molecule to 2-aza-1,4-pentadiene, while 1,3-diarylpropan-1-ones are formed as a result of the hydrolysis of 2-aza-1,4-pentadienes. It is found out that the mild conditions for the assembly of 1-pyrrolines (60 °C, 15 min) relate to the formation of complexes in the KO t Bu/DMSO superbasic medium, where the anion is readily accessible for the nucleophilic attack by the phenylacetylene molecule.

The Pd(II) complexes [Pd(Cp)(L) n ] m [BF 4 ] m were synthesized via the reaction of cationic acetylacetonate complexes with cyclopentadiene in the presence of BF 3 ∙OEt 2 ( n = 2, m = 1: L = PPh 3 ( 1 ), P( p -Tol) 3 , tris ( ortho -methoxyphenyl)phosphine (TOMPP), tri -2-furylphosphine, tri -2-thienylphosphine; n = 1, m = 1: L = dppf, dppp ( 2 ), dppb ( 3 ), 1,5-bis(diphenylphosphino)pentane; n = 1, m = 2 or 3: 1,6-bis(diphenylphosphino)hexane). Complexes 1 - 3 were characterized using X-ray diffractometry. The inspection of the crystal structures of the complexes enabled the recognition of (Cp - )⋯(Ph-group) and (Cp - )⋯(CH 2 -group) interactions, which are of C-H…π nature. The presence of these interactions was confirmed theoretically via DFT calculations using QTAIM analysis. The intermolecular interactions in the X-ray structures are non-covalent in origin with an estimated energy of 0.3-1.6 kcal/mol. The cationic palladium catalyst precursors with monophosphines were found to be active catalysts for the telomerization of 1,3-butadiene with methanol ( TON up to 2.4∙10 4 mol 1,3-butadiene per mol Pd with chemoselectivity of 82%). Complex [Pd(Cp)(TOMPP) 2 ]BF 4 was found to be an efficient catalyst for the polymerization of phenylacetylene (PA) (catalyst activities up to 8.9 × 10 3 g PA ·(mol Pd ·h) -1 were observed).

2-Acetyl-3,4-dihydropyrans, assembled from acetylene gas and ketones in a one-pot procedure, are ethynylated with acetylenes (KOBu t /DMSO, 15 °C, 2 h) to give acetylenic alcohols, which readily cyclize (TFA, rt, 5 min) to 7-ethynyl-6,8-dioxabicyclo[3.2.1]octanes in up to 92% yield. The ring closure of the above acetylenic alcohols can be performed without their isolation from the reaction mixture. Thus, the synthesis of 7-ethynyl-6,8-dioxabicyclo[3.2.1]octanes can be realized in just two synthetic operations from simple and available starting materials under mild transition-metal-free conditions.

The reactions of α-chalcogen, α-halo, or α-amino functionally substituted enals with terminal alkynes leading either to corresponding propargyl alcohols (for O-, S-, Cl-, and Br-bearing substrates) or unexpected 2-amino-2-cyclopentenones (for aminoenals) are described. The key feature of these reactions is the rearrangement of adducts bearing amino groups on silica gel that triggered further cyclization to five-membered carbocycles.

Tetrahydropyrrolo[1,2- d ]oxadiazoles have been synthesized in good-to-excellent yields via the cycloaddition of nitrile oxides ( in situ generated from aldoximes) to readily accessible functionalized Δ 1 -pyrrolines. The reaction proceeds smoothly at room temperature in a two-phase system in the presence of sodium hypochloride as an oxidant to diastereoselectively afford pharmaceutically prospective 1,2,4-oxadiazolines fused with a five-membered ring. The reaction tolerates a broad range of substrates, including those with oxidant-sensitive functional groups and competitive reaction sites.

Available pyrrolylalkynones with tetrahydroindolyl, cycloalkanopyrrolyl, and dihydrobenzo[ g ]indolyl moieties, acylethynylcycloalka[ b ]pyrroles, are readily annulated with Δ 1 -pyrrolines (MeCN/THF, 70 °C, 8 h) to afford a series of novel pyrrolo[1',2':2,3]imidazo[1,5- a ]indoles and cyclohepta[4,5]pyrrolo[1,2- c ]pyrrolo[1,2- a ]imidazoles functionalized with an acylethenyl group in up to an 81% yield. This original synthetic approach contributes to the arsenal of chemical methods promoting drug discovery. Photophysical studies show that some of the synthesized compounds, e.g., benzo[ g ]pyrroloimidazoindoles, are prospective candidates for TADF emitters of OLED.

It has been found that the addition of CH 2 CN - anion to the carbonyl group of acylethynylpyrroles, generated from acetonitrile and t -BuOK, results in the formation of acetylenic alcohols, which undergo unexpectedly easy (room temperature) decomposition to ethynylpyrroles and cyanomethylphenylketones ( retro -Favorsky reaction). This finding allows a robust synthesis of ethynylpyrroles in up to 95% yields to be developed. Since acylethynylpyrroles became available, the strategy thus found makes ethynylpyrroles more accessible than earlier. The quantum-chemical calculations (B2PLYP/6-311G**//B3LYP/6-311G**+C-PCM/acetonitrile) confirm the thermodynamic preference of the decomposition of the intermediate acetylenic alcohols to free ethynylpyrroles rather than their potassium derivatives.

An efficient method for the synthesis of pharmaceutically and high-tech prospective 2-(3-amino-2,4-dicyanophenyl)pyrroles (in up to 88% yield) via the reaction of easily available substituted acylethynylpyrroles with malononitrile has been developed. The reaction proceeds in the KOH/MeCN system at 0 °C for 2 h. In the case of 2-acylethynylpyrroles without substituents in the pyrrole ring, the reaction changes direction: instead of the target 2-(3-amino-2,4-dicyanophenyl)pyrroles, the unexpected formation of pyrrolyldienols and products of their intramolecular cyclization, 3-amino-1-acylethylidene-2-cyanopyrrolizines, is observed.

Photoinduced charge transfer affects the efficiency and selectivity of photochemical reactions. Incorporation of donating groups into the isoquinolinium core allowed us to overcome the photochemical inactivity of the corresponding dithienyl-substituted terarylenes, presumably by redirecting the charge transfer within the molecule, and gave access to a new family of thermally reversible photoswitches.

The article is devoted to heterocyclization of bis(2-chloroprop-2-en-1-yl)sulfide which proceeds in hydrazine hydrate-alkali medium and leads to formation of thiophene and pyrrole derivatives: previously described 4,5,9,10-tetrahydrocycloocta[1,2-c;5,8-c']dithiophene, as well as unknown hydrazone of 5-methylidene-3-methyldihydrothiophen-2-one and 1-amino-2-(propynylsulfanylpropenylsulfanyl)-3,5-dimethylpyrrole. Tentative mechanisms for the formation of the heterocyclic products are discussed. Obtained hydrazone of 5-methylidene-3-methyldihydrothiophen-2-one was used for the synthesis of a range of azine derivatives and in oxidation process with SeO 2 . The found reactions open up expedient approaches to the formation of various hardly accessible thiophene and pyrrole compounds from 2,3-dichloropropene and elemental sulfur as starting reagents.

Semistabilized diazatrienyl anions are generated by the reaction of 2-pyridylarylimines with arylacetylenes in superbase systems MO t Bu (M = Li, Na, K)/DMSO at ambient temperature for 15 min. The initial intermediate N -centered propargyl-1,3-diaza-1,3,5-trienyl anions undergo intermolecular cyclization to benzyl imidazopyridine anions (formally [3 + 2] cycloaddition), further intercepting a second molecule of the starting pyridylimines or a proton of medium to afford ( Z )-stilbene/imidazopyridine ensembles and benzyl imidazopyridines. The charge distribution in all intermediate anions and their synthetic evolution are consistent with quantum-chemical analysis (B2PLYPD/6-311+G**//B3LYP/6-31+G*).

Pure ( E )-alkenoyl dihydropyrans are stereoselectively assembled from 2-acetyl-3,4-dihydropyrans (products of one-pot self-organization of acetylene gas and ketones) and aromatic aldehydes (52-86% yields). Furthermore, ( E )-alkenoyl dihydropyrans undergo ring opening (acid hydrolysis) to afford 5-hydroxy-1,6-diketones (44-67% yields) and acetyl-2-( E )-styryl-2,3-dihydroxycyclopentanes (19-32% yields), both as single diastereomers.

Acylethynylpyrroles undergo facile (rt, MeCN or MeOH, 24-72 h) catalyst-free annulation with 1-pyrrolines to afford acylmethylenetetrahydrodipyrrolo[1,2- a :1',2'- c ]imidazoles in up to 93% yield and 90% E -stereoselectivity of the olefin moiety.

6-Methylene-5-oxaspiro[2.4]heptanones have been synthesized via base-catalyzed dimerization of available alkynyl cyclopropyl ketones. The reaction proceeds effectively in the presence of the t -BuOK/ t -BuOH/THF catalytic system at room temperature to afford the desired spirocycles in a regio- and stereoselective manner. A wider synthetic utility of alkynyl cyclopropyl ketones as novel building blocks was demonstrated by the synthesis of diverse spirocyclopropanes.

A convenient synthesis of pyrrolo[2,1- a ]isoquinolinium salts from 1-pyrrolines and alkynes through rhodium-catalyzed C-H functionalization/N-annulation tandem reaction is described. The protocol features a good substrate tolerance, mild reaction conditions, and high yields of target products. Exploration of the alkyne scope unexpectedly revealed a novel labile functional group-promoted rhodium-catalyzed C-H functionalization/C-annulation/elimination cascade reaction of 1-pyrrolines with electron-deficient alkynes.

The reaction of bromopropargylic alcohols with phenols in the presence of Cs 2 CO 3 /DMF affords α-phenoxy-α'-hydroxyketones (1:1 adducts) and α,α-diphenoxyketones (1:2 adducts) in up to 92% and 24% yields, respectively. Both products are formed via ring opening of the same intermediates, 1,3-dioxolan-2-ones, generated in situ from bromopropargylic alcohols and Cs 2 CO 3 ., (Copyright © 2022, Volostnykh et al.)

This article shows that two extremely important families of fused heterocyclic assemblies, namely 6-methylbenzo[4,5]imidazo[1,2- a ]pyrrolo[2,1- c ]pyrazine and 5a-methyl-5a,6-dihydro-5 H ,12 H -benzo[4,5]imidazo[1,2- a ]pyrrolo[1,2- d ]pyrazine, can be synthesized from only two available building blocks ( N -allenylpyrrole-2-carbaldehyde and o -phenylenediamine) by controlling only one reaction parameter (water content of the medium). It should be emphasized that the latter class of compounds (with an a/d arrangement) is previously unknown. If the allene group is introduced not into the starting compound, but during the reaction (in superbase media), a heterocyclic ensemble, 5-methylbenzo[4,5]imidazo[1,2- a ]pyrrolo[2,1- c ]pyrazines, with a different position of the methyl group is formed.

The high-resolution 1 H and 13 C NMR spectra (CHCl 3 solution) of sterically non-rigid heterospin complexes CoL 2 , CoL 2 -dipy, and CoL 2 -phen (where L is 4-(3',3',3'-trifluoro-2'-oxopropylidene)-2,2,5,5-tetramethyl-3-imidazolidine-1-oxyl) have been studied. The specific of the NMR phenomenon in paramagnetic systems is briefly analyzed. It is shown that the NMR spectra modified by hyperfine coupling can be successfully employed for investigation of the complexation processes. In accordance with the common protocols, the 1 H and 13 C NMR signals are assigned using the information on 13 С - 1 Н spin-spin coupling. In addition, the preliminarily recorded 1 H and 13 C NMR spectra of radical L are also used in the work. The temperature dependences of 1 H and 13 C paramagnetic shifts in the complexes under study have been obtained. A fundamental feature of these dependences is that they obey to the Curie law in a fairly wide temperature range (up to 100 °C). This observation can be used to control intramolecular processes of sterically nonrigid heterosystems in solutions., Competing Interests: The authors declare no conflict of interest., (© 2022 The Author(s).)

An unprecedented self-organization of three molecules of acetylene, two molecules of o -halo arylamine, and one molecule of water to 1-acetyl-1,3-bis(haloarylamines) in the KOH/DMSO system has been discovered. These high-value 1,3-bis(arylamines) are capable of acting as efficient "platform molecules" to provide one-pot access to hexahydropyrrolo[3,2- b ]indoles, 3-haloarylamino-pyrrolidines, benzyliden piperidinols, and other functionalized diamines.

N -Benzyl ketimines undergo [3 + 2] cycloaddition with arylacetylenes in the KOBu t /DMSO solution to 2,3,5-triarylpyrrolines, which are oxidized (chloranil, DDQ) in situ to 2,3,5-triaryl-2 H -pyrroles in 53-71% yields. The intermediate 1-pyrrolines can be isolated in 31-91% yields and separately oxidized to the corresponding 2 H -pyrroles.

An efficient method for the synthesis of pharmaceutically prospective pyrrole-aminopyrimidine ensembles (in up to 91% yield) by the cyclocondensation of easily available acylethynylpyrroles with guanidine nitrate has been developed. The reaction proceeds under heating (110-115 °C, 4 h) in the KOH/DMSO system. In the case of 2-benzoylethynylpyrrole, the unexpected addition of the formed pyrrole-aminopyrimidine as N- (NH moiety of the pyrrole ring) and C- (CH of aminopyrimidine) nucleophiles to the triple bond is observed.

Expedient protocols for the synthesis of three types of highly functionalized azaheterocyclic scaffolds (dihydropyridazines, tetrahydropyridazines, and partially saturated tricyclic systems) from readily available hydroxypyrrolines and hydrazides are described. The directions of the transformation of a common initial intermediate, namely a Brønsted acid-activated hydroxypyrroline, depend on the reaction conditions and the structure of the hydrazides., (Copyright © 2021, Shabalin et al.)

Highly arylated α-alkenyl-β-diketones are synthesized via a two-step sequence consisting of ( i ) potassium tert -butoxide/DMSO-catalyzed ( E )-stereoselective C-H functionalization of ketones with acetylenes followed by ( ii ) magnesium bromide etherate/DIPEA-soft enolization of the formed β,γ-unsaturated ketones and regioselective acylation with acyl chlorides. The method is compatible with a broad range of substrates and shown to be applicable as an intermediate stage in the construction of polyarylated heterocycles.

Unique bridgehead nitrones, 8-oxa-6-azabicyclo[3.2.1]oct-6-ene 6-oxides, have been assembled diastereoselectively via acetyldihydropyrans, products of one-pot self-organization of two molecules of ketones and two molecules of acetylene, which after oximation undergo acid-catalyzed ring closure. The proposed mechanism includes the enol double-bond protonation, followed by intramolecular cyclization involving the interaction of the carbocation formed with a nitrogen atom. A broad range of substrates tolerate this facile transformation, in which the bridgehead nitrones were isolated in high yields.

Several imines, readily derived from aryl methyl ketones and benzylamines, react with acetylene gas in KOBu t /DMSO system to afford 2-azadienes stereoselectively. This new C-C bond constructing reaction involves, instead of the expected ethynylation of the C═N bond, the addition of azaallyl anions to the triple bond of acetylene.

Aldimines react with aryl- and hetarylacetylenes in the presence of KOBu t /dimethyl sulfoxide (DMSO) or NaOBu t /DMSO systems under exceptionally mild conditions (14 °C, 1 h) to afford C-H-vinylated products, 1-azadienes of E configuration relative to the C-C bond, in up to 72% yield. Vinylation involves the unprecedentedly fast multiposition proton transfer in the intermediate adducts of acetylene to the C═N bond. This new Csp 2 -Csp 2 bond-forming reaction opens a straightforward pot-, atom-, step-, and energy-economic access to synthetically valuable 1-azadienes.

Under natural conditions, biodegradation processes proceed slowly, especially in regions with low temperature. To activate vital processes in hydrocarbon-oxidizing microorganisms at low temperatures, biologically active compounds can be employed as growth stimulants. A low-temperature (10 °C) study has shown that tris-(2 hydroxyethyl) ammonium arylchalcogenylacetates, "protatranes" exert an effect on the growth of hydrocarbon-oxidizing strains of Rhodococcus erythropolis and Pseudomonas fluorescens , isolated from natural oil seepage on Lake Baikal. It has been found that "protatranes", at microconcentrations, increase the growth rate of R. erythropolis bacteria by 2-16 times. It has been established that compounds slightly effect the growth of P. fluorescens . The positive effect of "protatranes" compounds on the growth rate of hydrocarbon-oxidizing microorganisms at low positive temperatures can be used for the development of environmentally benign methods for the restoration of natural objects after their contamination with oil., Competing Interests: The authors declare that they have no conflict of interest.

A straightforward acetylene-based scalable strategy for the synthesis of highly functionalized N-aminoindoles has been discovered. This pot-, atom-, step-, and energy-economic strategy includes two simple stages: (i) a one-pot multimolecular (2 + 2) diastereoselective assembly of 6,8-dioxabicyclo[3.2.1]octanes (6,8-DOBCOs) from acetylene gas and ketones in the KOH/DMSO two-phase superbase catalytic system and (ii) a mild (rt, CF 3 COOH) cascade transformation of 6,8-DOBCOs under the action of hydrazines to afford N-(arylamino)-3-(acylpropyl)indoles in good yields.

Pharmaceutically related bridgehead dihydro-1,3,4-oxadiazines are synthesized in up to 94% yield by the acid-catalyzed diastereoselective reaction of hydrazine hydrate with 6,8-dioxabicyclo[3.2.1]octanes (6,8-DOBCOs), the products of the superbase-promoted self-organization of acetylene with ketones. The synthesis covers a diverse range of alkylaromatic ketones having F-, Cl-, Br-, alkoxy-, CF3- and aryl substituents in different positions of the aromatic rings.

Dienyl derivatives of 6,8-dioxabicyclo[3.2.1]octanes, closely related to naturally abundant molecules, have been synthesized from 2-acetyl-3,4-dihydropyrans (readily available from ketones and acetylene in two steps), which further add to aryl(hetaryl)acetylenes in the KOBu t /DMSO superbase system (105 °C, 1.5 h) to stereoselectively give the corresponding E-styryl adducts. The latter undergo ring closure (NH 4 Cl/H 2 O, acetonitrile, reflux, 8 h) to form the 6,8-dioxabicyclo[3.2.1]octane core decorated with the (1 Z,3 E)-diene substituent.

Transition metal-free one-pot reaction of quinolines with acylarylacetylenes and water proceeds in the presence of KOH (55-60 °C, MeCN, 48 h) to afford 2-aryl-3-acylquinolines in up to 66% yield. Here, a formal replacement of the acetylene moiety by the aryl and acyl substituents in the quinoline scaffold takes place. In fact, it has been proved experimentally that the reaction involves the ring cleavage, accompanied by the rearrangement and insertion of the electron-deficient acetylene moiety to form a dihydroquinoline intermediate with an aldehyde functional group in position 4. This intermediate gives the corresponding doubly functionalized quinolines.

On the example of menthofuran, a naturally abundant compound, it has been shown for the first time that the furan ring can be readily cross-coupled with acylhaloacetylenes in the solid Al 2 O 3 powder at room temperature to afford the corresponding 2-ethynyl derivatives in up to 88% yield. The reaction represents a ring closing/ring opening process that includes reversible formation of the intermediate cycloadducts further producing acetylene derivatives with elimination of HHal., (© 2018 Elsevier Ltd. All rights reserved.)

A detailed study of the reaction of trifluoroacetylated acetylenes and aryl (alkyl) hydrazines was performed, aimed to the regioselective synthesis of 3- or 5-trifluoromethylated pyrazoles. It was found that the regioselectivity of reaction depends dramatically on the solvent nature. Highly polar protic solvents (hexafluoroisopropanol) favor the formation of 3-trifluoromethylpyrazoles. In contrast, when the reaction was performed in polar aprotic solvents (DMSO), the formation of their 5-CF 3 -substituted isomers was preferentially observed. Alternatively, the regioselective assembly of 3-CF 3 -substituted pyrazoles can be performed via two-step one-pot procedure. The reaction of trifluoromethylated ynones with aryl (alkyl) hydrazines in the presence of acidic catalysts leads to formation of the corresponding hydrazones. The latter can be smoothly transformed into 3-CF 3 -pyrazoles by treatment with a base. This solvent-switchable procedure was used for the preparation of such important drugs as Celebrex and SC-560 as well as their isomers in gram scale. The possible reaction mechanism is discussed.

The products of the one-pot assembly of acetylene and ketones in the KOH/DMSO system, 7-methylene-6,8-dioxabicyclo[3.2.1]octanes, undergo an acid-catalyzed (CF 3 COOH, room temperature) rearrangement to rarely substituted cyclopentadienes in good-to-excellent yields. The mechanism of the rearrangement has been supported by the isolation and corresponding transformations of two intermediates.

A concise, atom-economic strategy for the synthesis of pyrrolizines with amino and keto substituents has been developed. It includes the following key steps: (i) the base-catalyzed (K 3 PO 4 /DMSO) addition of a benzylamine to 2-acylethynylpyrroles and (ii) noncatalyzed addition of enaminones obtained to the triple bond of acylacetylenes followed by intramolecular cyclization of the intermediate pentadiendiones thus formed to the target 1-(benzylamino)-2-acyl-3-methylenoacylpyrrolizines.

The three-component reaction of ketones, arylacetylenes, and guanidine catalyzed by the KOBu t /DMSO system leads to 2-aminopyrimidines in up to 80% yield. Depending on structure of the starting ketones, the aromatization of intermediate dihydropyrimidines occurs either with loss of hydrogen molecules or methylbenzenes. The latter process takes place in the ketones, in which one of the substituents is not a methyl group. The reaction conditions are tolerable for dialkyl-, aryl(hetaryl) alkyl-, and cycloalkyl ketones.

A highly efficient method for the selective synthesis of trifluoromethylated morpholines (4-oxa-1-azabicyclo[4.1.0]heptanes) and so far unknown 1,4-oxazepanes (2,8-dioxa-5-azabicyclo[5.1.0]octanes) based on a domino reaction of fluorinated α-bromoenones with β-amino alcohols was elaborated. The assembly of both heterocyclic systems is initiated by an aza-Michael reaction followed by intramolecular cyclization. The conditions for total control of selectivity of the reaction were found.

KO(t)Bu/DMSO-promoted C-H functionalization of acetylarenes with arylacetylenes (100 °C, 30 min), generating β,γ-ethylenic ketones, triggers upon further heating (100 °C, 4 h, with or without acidifying additive) the cascade assembly of acyl terphenyls and higher polyaromatics in good yields.

The reactions of trifluoromethylated 2-bromoenones and N,N'-dialkyl-1,2-diamines have been studied. Depending on the structures of the starting compounds, the formation of 2-trifluoroacetylpiperazine or 3-trifluoromethylpiperazine-2-ones was observed. The mechanism of the reaction is discussed in terms of multistep processes involving sequential substitution of bromine in the starting α-bromoenones and intramolecular cyclization of the captodative aminoenones as key intermediates to form the target heterocycles. The results of theoretical calculations are in perfect agreement with the experimental data. The unique role of the trifluoromethyl group in this reaction is demonstrated., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)