A. G. Mal’kina

Stereoselective Synthesis of N -[( Z )-2-Cyano-1-Phenylethenyl]Benzimidazole-2-Carbothioamides by a Three-Component Reaction of 1-Substituted Benzimidazoles, Phenylcyanoacetylene, and Isothiocyanates

A new method has been developed for the synthesis of benzimidazole carbothioamides, which have potential pharmacological activity, by a three-component reaction of 1-substituted benzimidazoles, phenylcyanoacetylene, and methyl, allyl, or phenyl isothiocyanates. The reaction of these components proceeds under mild conditions in acetonitrile at 50-55°C for 12-20 h and stereoselectively leads to N-[(Z)-2-cyano-1-phenylethenyl]benzimidazole-2-carbothioamides in 43-82% yield.

Cyanoacetylene and Its Derivatives: XXXII. Addition of Ammonia and Methylamine to 4-Hydroxy-4,4-diphenyl-2-butynenitrile

Nucleophilic addition of ammonia (25% aqueous solution) and methylamine to 4-hydroxy-4,4-diphenyl-2-butynenitrile occurs under mild conditions to afford 4-amino(or methylamino)-2,5-dihydro-5,5-diphenyl-2-iminofurans. 4-Hydroxy-4,4-diphenyl-2-butynenitrile in anhydrous liquid ammonia gives rise to 3-amino-4-hydroxy-4,4-diphenyl-2- butenenitrile which is quantitatively converted into the corresponding iminodihydrofuran or iminodihydrofuran hydrochloride in the presence of 10 wt % of KOH or gaseous hydrogen chloride. 4-Amino- and 4-methylamino-2-iminofurans react with 4-hydroxy-4-methyl-2-pentynenitrile to give 3-(4-amino- and 4-methylamino-5,5-diphenyl-2,5-dihydrofuran-2-ylideneamino)-4-hydroxy-4-methyl-2-pentenenitriles.

Sulfurization of polymers. 4. Poly(4,5,6,7-tetrathiono-4,5,6,7-tetrahydrobenzothiophene-2,3-diyl) and related structures based on polystyrene and elemental sulfur

Polystyrene was exhaustively sulfurized with elemental sulfur at 190--370 °C to liberate hydrogen sulfide and to form black lustrous powders (the sulfur content was up to 67%) possessing conductivity (10–7--10–6 S cm–1 upon doping with I2), paramagnetic properties ((3.4--13)·1019 sp g–1, g = 2.0040--2.0046, ΔH = 0.36--0.47 mT), and redox properties. The use of these polymers as active cathode materials in lithium batteries allows their repeated cycling at a specific discharge capacity of up to 330 mA h g–1. The data of elemental analysis and differential scanning calorimetry, the IR and ESR spectra, the conductivities, and the character of electrochemical activity of the polymers synthesized are consistent with poly(4,5,6,7-tetrathiono-4,5,6,7-tetrahydrobenzothiophene-2,3-diyl) and related structures.

Opening of the pyridine ring in the system 1,1,1-trifluoro-4-phenylbut-3-yn-2-one–water. Stereoselective synthesis of 5-{[(1Z)-4,4,4-trifluoro-3-oxo-1-phenylbut-1-en-1-yl]amino}penta-2,4-dienal

We have recently discovered facile opening of the pyridine ring by the action of acyl(phenyl)acetylenes in the presence of a small amount of water (room temperature, solvent-free conditions, KOH or not), which leads to the formation of (Z)-(2-acyl-1-phenylethenyl)-5-aminopenta-2,4-dienals with high selectivity and up to 92% yield [1, 2]. Aminopentadienals (Zincke aldehydes) [3] are valuable building blocks for total syntheses of natural products, in particular of manzamine alkaloids [4–8] and alkaloid gelsemine [9], as well as of complex polycyclic structures via cascade reactions [9, 10]. However, the scope of application of these synthetic intermediates is limited due to their insufficient structural diversity [11].

Opening of pyridine ring with benzoyl(phenyl)acetylene in the presence of water with formation of 5-aminopenta-2,4-dienal

Opening of a pyridine ring is a possible synthetic route to 5-aminopenta-2,4-dienals and their derivatives, though aromaticity of the pyridine system creates a fundamental obstacle to such transformation. Efforts have been made to solve this problem [1, 2]. As a rule, the substrates were pyridinium salts or pyridine oxide, and hydroxide ion [3–6], ozone [7], Raney nickel [8], amines [9–12], Grignard compounds or acetylide ion [13, 14], and thiophosgene [15] were used as reagents; photolytic hydrolysis of pyridine was also performed [16, 17]. However, these studies have not received further development. We have found that heating of benzoyl(phenyl)acetylene (1) in boiling pyridine (115°C) in the presence of an equimolar amount of water is accompanied by opening of the pyridine ring with formation of isomeric 5-aminopenta-2,4-dienals E,E-2a and E,Z-2b a t a ra t io of (5–6) : 1 (unopt imized y ield 7%; Scheme 1). Isomer mixture 2a/2b was isolated by alumina column chromatography. Presumably, alkyne 1 reacts with pyridine to give zwitterionic adduct A which is converted into pyridinium hydroxide B as a result of proton transfer from water molecule to the carbanionic center. A covalent form of intermediate B, hydroxypyridine C undergoes rearrangement through cleavage of the N‒C bond, and Z,Z,Z-adduct D thus formed isomerizes to 2a/2b (Scheme 2).

Quantum chemical study of mechanisms of organic reactions: IV. Nucleophilic addition of ethylene glycol to 4-hydroxybut-2-ynenitrile

A theoretical mechanism has been proposed for nucleophilic addition of ethylene glycol to 4-hydroxybut-2-ynenitrile on the basis of DFT quantum chemical calculations at the B3LYP/6-311++G(d,p) level of theory. The reaction catalyzed by alkali involves nucleophilic attack by 2-hydroxyethoxide ion on the β-carbon atom of the acetylenic alcohol with intermediate formation of vinylic carbanion which undergoes intramolecular cyclization with closure of 1,3-dioxolane ring.

Quantum chemical study of mechanisms of organic reactions

A theoretical mechanism of nucleophilic addition of 1,3-diols to cyanoacetylene alcohols was proposed by the results of the quantum chemical study in terms of the density functional theory (DFT) by the B3LYP/6-311++G(d,p) method. In an alkaline medium, the reaction includes the nucleophilic attack of the ionized form of diol to the Cβ atom of cyanacetylene alcohol and proceeds via the formation of the intermediate vinyl carbanion that underwent intramolecular cyclization with 1,3-dioxane ring closure.

Signs of formation and chemical evolution of zwitterions in the reaction of 1-methylimidazole with cyanophenylacetylene and benzaldehyde

Primary monitoring of the three-component reaction of 1-methylimidazole with cyanophenylacetylene and benzaldehyde by EPR, UV, NMR, and IR spectroscopy has been carried out. Experimental evidence has been obtained for the formation of zwitterions and carbenes of the imidazole series as intermediates of a new functionalization reaction of the imidazole ring leading to 2-benzoyl-3-(1-methyl-1H-imidazol-2-yl)-3-phenylpropanenitrile.

13C-13C spin-spin coupling constants in structural studies: XLII. Stereochemical study on functionalized 2,5-dihydrofuran-2-imines

The configurations and conformations of twelve 5-imino-2,5-dihydrofuran-3-carboxamides and 5-imino-2,5-dihydrofuran-3-amines were determined by analysis of the experimental 13C-13C coupling constants and those calculated by nonempirical methods, as well as by quantum-chemical calculations of the total energies and optimization of geometric parameters of preferential conformations at the MP2/6-311G** level. All the examined compounds were found to be formed and to exist in solution as individual Z isomers with orthogonal orientation of the amino and dialkylamino groups and s-trans orientation of the carbamoyl group in the ring with restricted internal rotation about the C(O)-N bond.

Synthesis and properties of polyenic oligosulfides derived from acetylene and elemental sulfur

Oligosulfides derived from ethyne-1,2-dithiol were synthesized in up to 96% yield via insertion of elemental sulfur into the Na-Csp bond of sodium acetylides (HC≡CNa, NaC≡CSNa) in liquid ammonia, followed by hydrolysis and spontaneous oligomerization of ethynethiols, ethynedithiols, and mono-and bis-(polysulfanyl)ethynes (HC≡CSH, HSC≡CSH, HC≡CSxH, HSxC≡CSyH). The resulting polyenic oligosulfides were isolated as brown powders melting in the temperature range from 122 to 203°C and containing up to 77% of sulfur; they are sparingly soluble in organic solvents and are high-resistance semiconductors (10−13–10−14 S cm−1) possessing paramagnetic (1017–1018 spin g−1) and redox properties. According to the data of IR and ESR spectroscopy and cyclic voltammetry, the oligomers obtained consist mainly of different oligosulfide units, including oligothienothiophene structures. They also ensure a high discharge capacity (345–720 mA h g−1) of lithium sulfur rechargeable batteries.