A. M. Vasil’tsov

Selective synthesis of 1-vinylpyrroles directly from ketones and acetylene: Modification of trofimov reaction

Consecutive treatment of ketones with a system NH2OH·HCl-NaHCO3-DMSO and acetylene excess in the presence of KOH (100–120°C, initial acetylene pressure 12–15 at) led to a selective formation of 2-and 2,3-substituted 1-vinylpyrroles in 51–79% yields. Ketones of aliphatic, cycloaliphatic, aromatic, heteroaromatic, and tetrahydronaphthalene series were involved into the reaction.

1,2-Dioximes in the trofimov reaction

Abstract3,3′-Dimethyl-1,1′-divinyl-2,2′-dipyrrole was obtained during the reaction of 3,4-hexanedione dioximes with acetylene under pressure in the potassium hydroxide-DMSO system. In the case of 1,2-cyclohexanedione dioxime 2,2′-dipyrrole and 2-pyridyl-and 2-acylpyrroles were isolated. α-Benzil and α-furil dioximes give 3,4-diphenyl-and 3,4-di(2-furyl)-1,2,5-oxadiazoles respectively in addition to their mono-and divinyl derivatives.

Fluorescence quenching and laser photolysis of dipyrrolylbenzenes in the presence of chloromethanes

Fluorescence quenching of 1,4-bis(1H-pyrrol-1-yl)benzene, 1-(1H-pyrrol-2-yl)-1-(1-vinyl-1H-pyrrol-1-yl)benzene, and 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene with chloromethanes (methylene chloride, chloroform, and carbon tetrachloride) in solvents with different polarities follows electron-transfer mechanism. The occurrence of an electron-transfer step is confirmed by formation of short-lived pyrrolylbenzene radical cations. An exception is quenching of fluorescence of 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene in n-hexane in the presence of CCl4 and CHCl3 and in pure CCl4. In this case, neutral 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene·-Cl radical is formed via recombination of 1,4-bis(1-vinyl-1H-pyrrol-2-yl)benzene radical cation and chloride anion. A relation was found between the nature of the short-lived species detected by laser photolysis and stable product obtained by stationary photolysis.

13C-13C spin-spin coupling constants in structural studies: XL. Conformational analysis of N-vinylpyrroles

Conformational analysis of ten N-vinylpyrroles was performed on the basis of experimental 13C-1H and 13C-13C coupling constants and those calculated by high-level quantum-chemical methods, and principal relations between JCC and JCH values and stereochemical structure of these compounds were revealed.

Sulfurization of polymers. 6. Poly(vinylene polysulfide), poly(thienothiophene), and related structures from polyacetylene and elemental sulfur

Polyacetylene obtained by the dehydrochlorination of polyvinyl chloride in the NaOH—DMSO system undergoes sulfurization with elemental sulfur at 120—300 °C to liberate hydrogen sulfide and to form electroconducting (0.7·10–12—5.8·10–15Sm nm–1) and paramagnetic (1.5·1017—1.7·1019sp g–1, g = 2.0035—2.0045, ΔH= 0.44—0.66 mT) dark powders with a metallic luster. Their IR spectra and comparison with the samples of sulfurized polyethylene show that sulfurized polyacetylene contains poly(vinylene polysulfide), poly(thienothiophene), and related structures. The polymers afford the cathode discharge capacity of lithium batteries up to 950 mA h g–1(in the first cycle) and stable cycling at a level of 500—300 mA h g–1(25 cycles).

IMPROVED METHOD FOR THE SYNTHESIS OF 1-VINYLINDOLE

A highly efficient method has been developed for the synthesis of 1-vinylindole based on the vinylation of indole by acetylene at atmospheric pressure using the superbase KOH–DMSO catalytic system. The method allows the preparation of the 1-vinylindole in 94% yield with a purity of 99% (after a single distillation of the crude product).

Unusually Facile Pyrrolization of 2-Acetylcoumarone Oxime with Acetylene

The oxime of 2-acetylcoumarone reacts with acetylene under pressure in the system KOH-DMSO unusually readily forming 2-(2-pyrrolyl)coumarone and the corresponding O-vinyl oxime. Under more rigid conditions 2-(1-vinyl-2-pyrrolyl)coumarone is formed. The possibility of a two-stage transformation of 2-acylcoumarones into 2-pyrrolylcoumarones has therefore been demonstrated for the first time.

Formation of 5-phenyl-1-vinyl-1H-pyrrole-2-carbonitrile in the vinylation of 5-phenyl-1-vinyl-1H-pyrrole-2-carbaldehyde oxime with acetylene

It is known that ketone oximes react with acetylene in the superbasic system KOH–DMSO to give O-vinyloximes which readily undergo rearrangement into pyrroles (Trofimov reaction [1–3]). However, vinylation of 5-phenyl-1-vinyl-1H-pyrrole-2-carbaldehyde oxime (I) under analogous conditions gave exclusively 5-phenyl-1-vinyl-1H-pyrrole-2-carbonitrile (III, yield 67%) instead of expected O-vinyloxime II. It could be presumed that compound III was formed via dehydration of initial oxime I. Dehydration of aldehyde oximes to the corresponding nitriles in the system KOH–DMSO was described in [4]. However, oxime I almost did not undergo dehydration in the absence of acetylene (the yield of nitrile III did not exceed 4%). Therefore, we concluded that 5-phenyl-1vinyl-1H-pyrrol-2-carbonitrile (III) is formed as a result of elimination of vinyl alcohol (acetaldehyde) from O-vinyloxime II.

A quantum chemical study of the mechanism of the regioselective domino-reaction of O-vinyl-2-tetralone oxime

Quantum chemical (DFT) methods are used to study the mechanisms of intramolecular rearrangements (domino-transformations) in O-vinyl-2-tetralone oxime, which potentially can produce both conjugated and non-conjugated dihydrobenzindoles. Transition states of elementary reaction steps are localized. The 1,3-prototropic shift promoted by a mediator molecule (H2O) is the limiting step. An activation barrier of the formation of conjugated indole is 4.14 kcal/mol lower than the formation channel on the non-conjugated analog. Activation barriers of syn-(Z)/anti-(E)-isomerization in O-vinyl-2-tetralone oxime are analyzed. It is shown that with regard to barriers of the promoted prototropic shift, Z/E-isomerization is a rapid process.

Copolymerization of N-vinylpyrrole-2-carbaldehydes with styrene, N-vinylpyrrolidone, and ethylene glycol vinyl glycidyl ether

Polyfunctional reactive copolymers of N-vinylpyrrole-2-carbaldehydes with styrene, N-vinylpyrrolidone, and ethylene glycol vinyl glycidyl ether are synthesized in the presence of AIBN (2 wt %, 80°C, 50 h) with a yield of up to 98% and a molecular mass of up to 4800. The copolymers show paramagnetic behavior (N = 2.0 × 1015−2.0 × 1017 g−1) and possess the properties of organic semiconductors (σ = 0.9 × 10−11–2.8 × 10−7 S/cm after doping with I2).