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Substituted acrylamides have found an extensive application in organic and medical chemistry therefore it is very important to get insight into their features such as electronic structure, spectral properties, and stereochemical transformations. A correct interpretation of the chemical behavior and biological activity of these heteroatomic systems is impossible without knowledge of the structure of stereodynamic forms and factors determining their relative stability. The structure and peculiarities of stereodynamic behavior of substituted acrylamides and their model compounds were studied by dynamic and multinuclear

Environmentally friendly synthetic methods were developed for the selective preparation of new 2,3-dihydro-1,4-thiaselenine derivatives in high yields based on the reactions of 2-bromomethyl-1,3-thiaselenole with alcohols and water at room temperature. The reaction of 2-bromomethyl-1,3-thiaselenole with alcohols was accompanied by a rearrangement with ring extension, leading to six-membered heterocyclic compounds, a new family of 2-organyloxy-2,3-dihydro-1,4-thiaselenines, in 80–96% yields. The remarkable cascade reactions of 2-bromomethyl-1,3-thiaselenole with water afforded 2,3-dihydro-1,4-thiaselenines functionalized with the (Z)-S-CH=CH-Se fragment and one or two highly reactive aldehyde groups. The latter aldehydes were functionalized by the reactions with alcohols and glycols to give new polyfunctionalized compounds, containing two double bonds, two sulfur atoms, two selenium atoms, and two or four oxygen atoms, in high yields.

Sequential processing of monolithiated tertiary propargylamines with 2-(vinyloxy)ethyl isothiocyanate and t-BuOK–DMSO results in the introduction of a highly reactive 2-(vinyloxy)ethyl group at the position 1 of the pyrrole ring thus formed. In this way, a series of new 5-sulfanyl-1-[2-(vinyloxy)ethyl]-1H-pyrrol-2-amines were obtained in a yield of up to 92%. The latter in the presence of t-BuOK–DMSO system (110–120 °C, 10–15 min) eliminates vinyl alcohol to give rare-functionalized 1-vinylpyrroles, namely 5-sulfanyl-1-vinyl-1H-pyrrol-2-amines, inaccessible by the known methods.

Deprotonative metalation of N-isopropenyl-1H-pyrroles with superbases followed by trapping with a variety of electrophiles was studied as an effective tool for the regioselective functionalization of 1H-pyrroles.

The synthetic application of the new reagent, 1,2-bis[(Z)-2-(vinylsulfanyl)ethenyl] diselane, was described for the first time. This reagent was obtained in high yield by a chemo-, regio- and stereoselective reaction of...

To date, not a single representative of 2,3-dihydro-1,4-thiaselenin-2-yl selenides has been described in the literature. The reaction of 2-bromomethyl-1,3-thiaselenole with potassium selenocyanate at low temperature was accompanied by a rearrangement with ring expansion leading to six-membered 2,3-dihydro-1,4-thiaselenin-2-yl selenocyanate, which was used for the generation of sodium dihydro-1,4-thiaselenin-2-yl selenolate. The latter intermediate was involved in situ in the nucleophilic substitution and addition reactions under phase transfer catalysis conditions. The nucleophilic substitution reactions with alkyl halides gave alkyl, allyl and propargyl 2,3-dihydro-1,4-thiaselenin-2-yl selenides in 93–98% yields. The addition reactions of dihydro-1,4-thiaselenin-2-yl selenolate anion to alkyl acrylates, acrylonitrile and alkyl propiolates proceeded in a regio- and stereoselective fashion affording corresponding functionalized 2,3-dihydro-1,4-thiaselenin-2-yl selenides in 93–98% yields. Thus, the regio- and stereoselective one-pot synthesis of a novel family of 2,3-dihydro-1,4-thiaselenin-2-yl selenides has been developed based 2-bromomethyl-1,3-thiaselenole, potassium selenocyanate, alkyl halides and compound with activated double and triple bonds.

Terminal acylacetylenes, typical electron-deficient acetylenes, drive SHN cross-coupling of pyridines with secondary phosphine chalcogenides under metal-free mild conditions (20–75 °C) to afford 4-chalcogenophosphorylpyridines in up to 70% yield. The reaction proceeds via 2,4-migration of chalcogenophosphoryl groups in the intermediate 1-acylvinyl-2-phosphoryl dihydropyridines with simultaneous redox elimination of the vinyl ketone oligomers. These results are generalized in a concept of trimodal (polarization/deprotonation/oxidation) catalyst-like assistance of electron-deficient acetylenes in SHN reaction of the pyridinoid heterocycles with PH-nucleophiles, which comprises: (i) repolarization (umpolung) of the pyridine ring, (ii) deprotonation of secondary phosphine chalcogenides to generate phosphorus-centered anions and (iii) oxidation of the dihydro intermediates.

Reactions between 3-phenyl-2-propynenitrile, secondary phosphine oxides and pyridinoids have been implemented and studied. Pyridine and isoquinoline react with propynenitrile and phosphine oxides at room temperature according to the N-vinylation/C-phosphorylation scheme to afford (Z)-N-(2-cyano-1-phenyl)ethenyl phosphoryl-1,4-dihydropyridines or -1,2-dihydroiso quinolines. In the case of pyridine on heating (80–85 °°°C), the reaction gives 4-phosphorylpyridines ( S N H Ar reaction) and 3-phenyl-acrylonitrile oligomers.

The reaction of 2-(bromomethyl)-1,3-thiaselenole with potassium selenocyanate proceeded via a rearrangement with ring expansion, leading to a six-membered 2,3-dihydro-1,4-thiaselenin-2-yl selenocyanate (kinetic product) which in turn underwent rearrangement with ring contraction to a 1,3-thiaselenol-2-ylmethyl selenocyanate (thermodynamic product). These rearrangements occurred by a nucleophilic attack of the selenocyanate anion at two different carbon atoms of the seleniranium intermediate. The efficient regioselective synthesis of alkyl, allyl, 2-propynyl, benzyl, 4-fluorobenzyl, and 2-pyridinylmethyl 1,3-thiaselenol-2-ylmethyl selenides was developed based on the generation of sodium 1,3-thiaselenol-2-ylmethylselenolate from 1,3-thiaselenol-2-ylmethyl selenocyanate or bis(1,3-thiaselenol-2-ylmethyl) diselenide followed by nucleophilic substitution reactions. Sodium 1,3-thiaselenol-2-ylmethylselenolate underwent nucleophilic addition to alkyl propiolates in a regio- and stereoselective manner affording 1,3-thiaselenol-2-ylmethyl vinyl selenides in high yields predominantly with Z-configuration. Not a single representative of the 1,3-thiaselenol-2-ylmethyl selenide scaffold has been previously described in the literature.

Quinolines undergo catalyst-free double CH-functionalization upon treatment with secondary phosphine oxides (70-75 °C, 20-48 h) followed by oxidation of the intermediate 2,4-bisphosphoryltetrahydroquinolines with chloranil. The yields of the target 2,4-bisphosphorylated quinolines are up to 77%. Thus, a double-SNHAr reaction sequence in the same molecule of quinoline has been realized. In the case of 2,4-bisphenylphosphoryltetrahydroquinolines, the aromatization occurs with elimination of one molecule of diphenylphosphine oxide to afford the products of monofunctionalization, 4-diphenylphosphorylquinolines, in 40-45% yields.

A new method for regioselective nucleophilic substitution at one of the three possible reaction centers of seleniranium cation, generated from 2-(bromomethyl)-1,3-thiaselenole, with mono- and bicyclic nitrogen-containing heteroaromatic thiols was developed. The reaction was directed at the carbon atom attached to sulfur atom of the intermediate seleniranium cation and was accompanied by rearrangement with ring expansion to afford in high yields new (2,3-dihydro-1,4-thiaselenin-2-yl)sulfanyl-substituted pharmacophoric heterocycles with one to four nitrogen atoms. The reaction of 2-(bromomethyl)-1,3-thiaselenole and quinoxaline-2,3-dithiol provided the corresponding 2,3-bis[(2,3-dihydro-1,4-thiaselenin-2-yl)sulfanyl] derivative. In the case of 5-methyl-1,3,4-thiadiazole-2-thiol, the reaction in MeCN led to 2-methyl-5-{[(1,3-thiaselenol-2-yl)methyl]sulfanyl}-1,3,4-thiadiazole at the expense of rearrangement of the intermediate (2,3-dihydro-1,4-thiaselenin-2-yl)sulfanyl derivative in a form of hydrobromide salt with the ring contraction proceeding via seleniranium cation. The synthesized novel sulfur- and selenium-containing functionalized unsaturated heterocycles can be considered as potential scaffolds for medicinal chemistry.

The Pd/Cu-catalyzed Sonogashira reaction of (E,E)-bis(2-bromovinyl) selenide and (E,E)-bis(1-bromo-1-hexen-2-yl) selenide with terminal alkynes was found to proceed at room temperature involving both bromine atoms and the selanyl function. As a result, new bis-(1,3-enynyl) selenides and enediyne hydrocarbons are formed with a complete retention of the stereoconfiguration of the initial selenides. Due to steric hindrances in the cross-coupling at the selenyl function in the case of (E,E)-bis(1-bromo-1-hexen-2-yl) selenide, the second process is realized to a lesser extent than with unsubstituted (E,E)-bis(2-bromovinyl) selenide.

Chemoselective and atom-economical methods for the synthesis of ferrocene diethenyl ethers have been developed via direct base-catalyzed addition of 1,1′-bis(hydroxymethyl)ferrocene to various acetylenes. This ferrocene diol has been shown to be capable of adding to acetylene (KOH/DMSO, 70–80 °C, 1–3 h), propyne (KOH/DMSO, 70 °C, 12 h), phenylethyne (KOH/DMSO, 20–25 °C, 48 h), alkylpropiolates (DABCO, 10 mol%/CH2Cl2, 20–25 °C, 0.5 h), and acylacetylenes (DABCO, 1 mol%/CH2Cl2, 20–25 °C, 0.5 h) to afford the corresponding diethenyl ethers in 73–98% yields.

An efficient synthesis of the earlier unknown trichloro- and tribromo(2-ahkoxy-2-phenylethyl)-λ4-tellanes with yields of 90 to 100% has been developed basing on alkoxytelluration of styrene with tellurium tetrachloride or tetrabromide in the presence of alcohols. The reduction of tellanes in the NaBH4-H2O-THF and Na2S2O5-H2O-C6H6 systems has afforded bis(2-alkoxy-2-phenylethyl)ditellanes in up to 95% yield.

2-[(5-Amino-1H-pyrrol-2-yl)sulfanyl]acetic acid esters have been synthesized in up to 77% yield by the one-pot reaction of lithiated propargylamines with isothiocyanates followed by sequential treatment with t-BuOK–DMSO and alkyl 2-bromoacetates. The process occurs through the initial formation of the thiophene core, followed by its recyclization into the pyrrole nucleus at a higher temperature (ca. 45–60 °C).

Quinolines react with acylacetylenes and secondary phosphine chalcogenides at 20–75 °C to afford N-acylvinyl-2(1)-chalcogenophosphoryldihydroquinolines in good and excellent yields. Unlike the pyri...

Regio- and stereoselective ring-opening reaction of 2-bromomethyl-1,3-thiaselenole with thiols proceeded as nucleophilic attack at the selenium atom of seleniranium intermediate affording unsaturated selanyl sulfides, (Z)-CH2=CHSCH=CHSeSR, in up to 93% yield. Dithiols were involved in this reaction giving symmetrical polyunsaturated compounds with two S–Se bonds in 70–75% yields. Efficient synthesis of 2-(organylsulfanyl)-2,3-dihydro-1,4-thiaselenines in 69–96% yields was developed by the acid-catalyzed cyclization of the unsaturated selanyl sulfides. Mild reaction conditions (room temperature) and short reaction times are important features of this methodology.

A new methodology of nucleophilic substitution at three different centers of a seleniranium intermediate in reactions of 2-bromomethyl-1,3-thiaselenole with mercapto benzazoles containing various combinations of heteroatoms (N, O and S) was developed. The reactions were accompanied by rearrangement with ring extension affording a new family of 2,3-dihydro-1,4-thiaselenins functionalized with benzazoles in high yields. The latter compounds in turn underwent rearrangement with ring contraction via an intermediate seleniranium cation giving new 1,3-thiaselenole ensembles in high yields. The reaction of 2-bromomethyl-1,3-thiaselenole with 1,3-benzothiazole-2-thiol proceeded in a stereoselective manner leading to (Z,Z)-CH2CHSCHCHSeSeCHCHSCHCH2 as the result of nucleophilic attack at the selenium atom of the seleniranium intermediate with ring opening followed by disproportionation.

The regioselective one-pot synthesis of novel functionalized 2,3-dihydro-1,4-thiaselenin-2-ylsufanyl derivatives in high yields based on 2-bromomethyl-1,3-thiaselenole and activated alkenes was developed under phase transfer catalysis conditions. The reactions proceed under mild conditions at room temperature in a regioselective manner with the addition of sodium dihydro-1,4-thiaselenin-2-ylthiolate exclusively at the terminal carbon atom of the double bond of vinyl methyl ketone, alkylacrylates, acrylamide, acrylonitrile, divinyl sulfone, and divinyl sulfoxide. The sodium dihydro-1,4-thiaselenin-2-ylthiolate was generated from 2-[amino(imino)methyl]sulfanyl-2,3-dihydro-1,4-thiaselenine hydrobromide. The latter compound was obtained by the reaction of 2-bromomethyl-1,3-thiaselenole with thiourea, which was accompanied by a rearrangement with ring expansion to the six-membered heterocycle. The obtained 2,3-dihydro-1,4-thiaselenin-2-ylsufanyl derivatives are a novel family of compounds with putative biological activity. The addition products of sodium dihydro-1,4-thiaselenin-2-ylthiolate at one double bond of divinyl sulfone and divinyl sulfoxide, containing vinylsulfonyl and vinylsulfinyl groups, are capable of further addition reactions. A possibility to obtain corresponding alcohol derivatives was shown in the reaction with vinyl methyl ketone.

Quinolines undergo catalyst-free double CH-functionalization upon treatment with secondary phosphine oxides (70-75 °C, 20-48 h) followed by oxidation of the intermediate 2,4-bisphosphoryltetrahydroquinolines with chloranil. The yields of the target 2,4-bisphosphorylated quinolines are up to 77%. Thus, a double-S

The original goal of this research was to study stereochemistry of selenium dihalides addition to cycloalkenes and properties of obtained products. Remarkable alkene-to-alkene and alkene-to-alkyne transfer reactions of selenium dibromide and PhSeBr were discovered during this research. The adducts of selenium dibromide with alkenes or cycloalkenes easily exchange SeBr2 with other unsaturated compounds, including acetylenes, at room temperature, in acetonitrile. Similar alkene-to-alkene and alkene-to-alkyne transfer reactions of the PhSeBr adducts with alkenes or cycloalkenes take place. The supposed reaction pathway includes the selenium group transfer from seleniranium species to alkenes or alkynes. It was found that the efficient SeBr2 and PhSeBr transfer reagents are Se(CH2CH2Br)2 and PhSeCH2CH2Br, which liberate ethylene, leading to a shift in equilibrium. The regioselective and stereoselective synthesis of bis(E-2-bromovinyl) selenides and unsymmetrical E-2-bromovinyl selenides was developed based on the SeBr2 and PhSeBr transfer reactions which proceeded with higher selectivity compared to analogous addition reactions of SeBr2 and PhSeBr to alkynes under the same conditions.

Acridine adds secondary phosphine chalcogenides HP(X)R2 (X = O, S, Se; R = Ar, ArAlk) under catalyst-free conditions at 70–75 °C (both in the presence and absence of the electron-deficient acetylenes) to give 9-chalcogenophosphoryl-9,10-dihydroacridines in 61–94% yields. This contrasts with pyridines, which under similar conditions undergo an SNHAr reaction, wherein electron-deficient acetylenes play the role of oxidants. For acridine, the SNHAr step has been accomplished by the oxidation of the intermediate 9-phosphoryl-9,10-dihydroacridines (X = O) with chloranil.

The previously unknown regioselective reactions of 2-(bromomethyl)-1,3-thiaselenole with 1-methyl-1H-imidazol-2-thiol were used to develop efficient synthetic approaches to novel heterocyclic systems, involving C–S and C–N bond formation. The reactions are accompanied by the rearrangements of the starting heterocycles, giving rise to diverse potentially biologically active heterocyclic systems.

Efficient methods for the preparation of trichloro- and tribromo(2-ethoxyalkyl)-λ4-tellanes in 80 to 100% yield have been developed on the basis of ethoxytelluration of hex-1-ene, hept-1-ene, and oct-1-ene with tellurium tetrahalides. Tribromo(2-ethoxyalkyl)-λ4-tellanes have been reduced to 1,2-bis(2-ethoxyalkyl)ditellanes in 92–95% yield with the system NaBH4–H2O–THF.

Treatment of 2-aza-1,3,5-trienes, methyl N-[2-alkoxy-1-(prop-2-ynylsulfanyl)buta-1,3-dienyl]- and methyl N-[1-(allylsulfanyl)-2-alkoxybuta-1,3-dienyl]iminoformates, which are easily obtained from lithiated alkoxyallenes, methoxymethyl isothiocyanate, and propargyl or allyl bromide, with t-BuOK or t-BuONa in DMSO–THF results in the formation of 5-ethynyl-2-vinyl- and 2,5-divinyl-1,3-thiazoles. The reactions are realized under mild conditions at ca. –30 °C for 30 minutes. An unprecedented structural transformation of the (prop-2-ynylsulfanyl)- and (allylsulfanyl)-substituted 2-aza-1,3,5-trienes into 1,3-thiazoles presumably occurs via α-deprotonation of the substituent at the sulfur atom (on the SCH2 group) followed by intramolecular [1,5]-cyclization at the imine group and aromatization (with elimination of MeOH).

N-[Chloro(dimethyl)silyl]methyl-N,N′-diphenylurea with intramolecular coordination bond C=O→Si was prepared by interaction of N,N′-diphenylurea with silane ClCH2SiMe2Cl. Structure of this compound was confirmed by 1H, 13C, 29Si NMR spectroscopy and X-ray diffraction analysis.

Regio- and stereoselective reactions of 2-bromomethyl-1,3-thiaselenole with water and ethylene glycol are accompanied by a rearrangement with the expansion of the five-membered ring to six-membered 2,3-dihydro-1,4-thiaselenine derivatives. The reactions proceed under unusually mild conditions at room temperature presumably via seleniranium intermediates involving a series of unexpected cascade transformations. First representatives of unsaturated polyfunctional 2,3-dihydro-1,4-thiaselenines bearing O-, S- and Se-containing substituents were obtained in up to 80% yield.

Efficient methods have been developed for regioselective synthesis of new organochalcogen compounds containing 2,3-dihydro-1-benzofuran-2-ylmethyl and 7-methyl-2,3-dihydro-1-benzofuran-2-ylmethyl substituents by reactions of selenium and sulfur dichlorides and tellurium tetrachloride with 2-allylphenol and 2-allyl-6-methylphenol.

Reaction of O-trimethylsilyl (O-TMS) derivatives of α-dimethylamino ketones with chloro(chloromethyl)dimethylsilane led to the formation of six-membered heterocyclic compounds with tetracoordinated silicon atom - 3,4-dihydro-2H-1,4,2-oxazasilin-4-ium chlorides. The exchange reactions of 2,2,4,4-tetramethyl-6-phenyl-3,4-dihydro-2H-1,4,2-oxazasilin-4-ium chloride were examined with Me3SiI and NaBPh4 and the corresponding iodide or tetraphenylborate of 2,2,4,4-tetramethyl-6-phenyl-3,4-dihydro-2H-1,4,2-oxazasilin-4-ium were isolated. 2,2,4,4-Tetramethyl-6-phenyl-3,4-dihydro-2H-1,4,2-oxazasilin-4-ium chloride easy reacts with MeOH to give N-((methoxydimethylsilyl)methyl)-N,N-dimethyl-2-oxo-2-phenylethanaminium chloride. The structure of synthesized compounds 10–15 was proved by multinuclear NMR spectroscopy, 11 was also characterised by X-ray crystallography.

Secondary phosphine selenides react with acylacetylenes in water to form bis(2-acylvinyl) selenides. The reaction proceeds without catalyst and organic solvent under mild conditions (70–72 °C, 3 h), the corresponding divinyl selenides being isolated as a mixture of (Z,Z)- and (E,Z)-isomers in a yield of up to 78%.

Derivatives of 2,3,6,7-tetrahydro-5H-[1,3]thiazolo[3,2-a]pyridine and 5,6-dihydropyridin-2(1H)-one were unexpectedly obtained at treating methyl 2-[(6-methyl-3-ethoxy-5,6-dihydropyridin-2-yl)sulfanyl]-acetate with a dilute solution of hydrochloric acid. Their formation resulted from the hydration of 5,6-dihydropyridine at the C=N bond accompanied with the elimination of a methyl 2-sulfanylacetate molecule and the addition of the methyl 2-sulfanylacetate to the second 5,6-dihydropyridine molecule at the C3=C4 bond followed by the elimination of a methanol molecule and the closure of a thiazole ring.

The reaction between 4-methylpyridine, alkyl propiolates, and secondary phosphine oxides proceeded as N-vinylation-C-phosphorylation with stereo- and regioselective formation of (E)-N-ethenyl-C2- phosphoryl-1,2-dihydropyridines [when using bis(2-phenylethyl)phosphine oxide] or (E)-N-ethenyl-C4- phosphoryl-1,4-dihydropyridines (when using diphenylphosphine oxide). The process occurred at 60–62°C within 3 h to give functional dihydropyridines in 40–82% yield. Under similar conditions, bis(2-phenylethyl) phosphine sulfide and selenide reacted with alkyl propiolates preferably by nucleophilic PH-monoaddition at the triple bond.

The 3,3-disubstitued 3-silaheterocyclohexane with an electronegative substituent at silicon, 3-fluoro-3-methyl-3-silatetrahydropyran 1, was synthesized, and its molecular structure and conformational properties studied by gas-phase electron diffraction (GED) and low temperature C-13 and F-19 NMR spectroscopy. Quantum-chemical calculations were carried out both for the isolated species and Hcomplexes in gas and in polar medium. The predominance of the 1-FeqMeax conformer (1-F-eq:1-F-ax ratio of 65:35, Delta G degrees = 0.37 kcal/mol) determined from GED is close to the theoretically estimated conformational equilibrium, especially at the DFT level. In solution, low temperature NMR spectroscopy showed no decoalescence of the signals in C-13 (down to 95 K) and F-19 NMR spectra (down to 123 K). However, the calculated F-19 chemical shift of -173.6 ppm for the 1-FeqMeax conformer practically coincides with the experimentally observed value (-173 to -175 ppm) as distinct from that for the 1-FaxMeeq conformer (-188.8 ppm), suggesting compound 1 to be anancomeric in solution, in compliance with its theoretical and experimental preference in the gas phase.