<Emphasis Type="Italic">Ab initio</Emphasis> quantum-chemical study of the reaction mechanisms of acetylene in superbasic media. Noncatalytic vinylation of methanol

The reaction profile of noncatalytic vinylation of methanol with acetylene was studied by ab initio quantum-chemical calculations for the gas phase and by calculations using a combined model that took into account the solvent (DMSO) effect. The reaction occurs via the formation of a prereaction complex of the methoxide ion with acetylene; at this stage, the acetylene molecule is already activated with respect to the proton. The observed stereospecific trans-addition in methanol vinylation in the gas phase and solution is provided by the lower activation barrier corresponding to the E structure of the acetylene molecule in the transition state and barrier-free protonation of the carbanion intermediate.     

Synthesis of glucosamine vinyl ether derivative and its deuterated analog

The use of calcium carbide (in the presence of H₂O) as a source of acetylene in the reaction with methyl 2-amino-4,6-O-benzylidene-2-deoxy-β-d-glucopyranoside under superbasic conditions (KF, KOH, DMSO, 130 °C, 3 h) led to the corresponding vinyl ether in 78% yield. The vinylation does not affect other reaction centers. Replacement of water with deuterium oxide in the reaction mixture gave a stable deuterated analog of this vinyl ether in 72% yield. The one-step isotopic enrichment was practically quantitative (isotopic purity >96%). Introduced deuterium atoms can be used as a convenient label in further transformations.

     

Synthesis of vinyl esters of organosilicon carboxylic acids

Conclusions The vinylation of -silicon-containing carboxylic acids by acetylene under the influence of zinc and cadmium salts was investigated. A method was found for producing organosilicon complex vinyl esters.     

Trofimov Reaction with Oximes Derived from Ketosteroids: Steroid-Pyrrole Structures

Steroidal ketone oximes, namely pregnenolone oxime, ⁵-cholesten-3-one oxime, and progesterone dioxime react with acetylene in superbasic systems (Trofimov reaction) to afford steroid-pyrrole assemblies. The process is accompanied by prototropic migration of double bonds in the steroid fragment and vinylation of hydroxy groups in sterols with acetylene. The O-vinyl group can readily be removed by methanolysis.     

Nucleophilic Addition to Acetylenes in Superbasic Catalytic Systems: XI. Transformations of Alkali Metal Hydroxides during Vinylation of 1-Heptanol with Acetylene under Elevated Pressure

Base-catalyzed addition of 1-heptanol to acetylene under elevated pressure of the latter is accompanied by side processes including formation of carboxylic acid salts (alkali metal heptanoates and acetates) with liberation of hydrogen and acetylene polymerization. The rate of acetylene absorption depends on the alkali metal nature and falls down in the series CsOH·H₂O RbOH·H₂O > 2KOH·H₂O > NaOH > LiOH. Approximately the same order is observed for variation of the rate of deactivation of the catalyst owing to its transformation into metal carboxylate. Dehydration of the catalyst accelerates both vinylation and acetylene polymerization.     

Indium triflate-catalyzed vinylation of beta-ketoesters with acetylene gas

[reaction: see text]. An In(OTf)(3)-catalyzed addition of a beta-ketoester to acetylene in the presence of molecular sieves produces a alpha-vinylated ketoester in good to excellent yield. The vinylation reaction proceeds without any loss of elements in starting molecules under solvent-free conditions and allows the use of welding-grade acetylene, providing a practical method for synthetic utilization of acetylene gas.     

Gas-Phase Vinylation of N-Methylacetamide

Catalysts for selective gas-phase vinylation of N-methylacetamide with acetylene were studied. These catalysts were obtained by applying to wide-pore silica gel of the CdO-K₂O-ZnO system or applying to commercial Al₂O₃ of the CdO-K₂O and CdO-K₂O-ZnO systems.     

Tuneable superbase-catalyzed vinylation of α-hydroxyalkylferrocenes with alkynes

Superbase-catalyzed (KOH/DMSO suspension as a catalyst) vinylation of hydroxymethyl- and hydroxyethylferrocenes with terminal and internal alkynes (acetylene, propyne, phenylacetylene, 3-ethynylpyridine, 1-propyn-1-yl-benzene, diphenylacetylene) affords hitherto unknown vinyl ethers of ferrocene in 30–93% yields depending on the alkyne structure and the tuneable ratio of reactants/KOH/DMSO. The vinylation smoothly proceeds under mild conditions (70–90 °C, 0.25–13 h). With unsubstituted acetylene the process is readily realized under atmospheric pressure (yield of the corresponding vinyl ethers is 81–90%) though under pressure (initial pressure at room temperature is 10–13 atm, maximum pressure is 13–16 atm at the reaction temperature) the yield is close to quantitative (93%). The synthesized compounds were characterized using ¹H and ¹³C NMR, and IR spectroscopy, as well as X-ray diffraction analysis.     

Vinylation of Tetrahydro-γ-carbolines

A convenient method for vinylation of tetrahydro-γ-carbolines with ethane-1,2-diyl dimethanesulfonate in the presence of sodium hydride was proposed.

     

On the anomalous behavior of thiodiglycol under conditions of the vinylation reaction

Conclusions The interaction of thiodiglycol with acetylene under the usual vinylation conditions is accompanied by an anomalous reaction, leading to vinyl ethers of monothioethylene glycol.     

Reactions of benzothiazole-2-thione and benzothiazole-2-one with acetylene

Reaction of benzothiazole-2-thione and benzothiazole-2-one with acetylene in the presence of potassium hydroxide or cadmium acetate gives 2-vinylthiobenzothiazole and 3-vinylbenzothiazol-2-one, respectively. Benzothiazole-2-thione is partially convened to benzothiazol-2-one by the action of Cd(OAc)₂. Under vinylation conditions the latter also forms 2-vinylthioaniline.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 270–271, February, 1991.     

Nanoporous crosslinked macrocyclic polyethers based on diethylene glycol divinyl ether and their superbase complexes with KOH

Nanoporous (11–12 nm) crosslinked macrocyclic polyethers with vinyloxy and hydroxyl groups have been synthesized by the free-radical polymerization of diethylene glycol divinyl ether (AIBN, 80°C, i-octane), followed by acidic hydrolysis. It has been shown that the polymers react with KOH to form insoluble superbase complexes and alcoholates capable of catalyzing vinylation of ethylene glycol by acetylene.     

An ab initio quantum chemical study of reaction mechanisms in the C2H2/CH3OH/KOH/DMSO system

An ab initio quantum chemical study (MP2/6-311++G**//B3LYP/6-31+G*) of a number of possible interactions is performed for the gas phase system of acetylene—potassium hydroxide-dimethylsulfoxide(DMSO)—methanol and with regard to the solvent effect within the continuum model. Key structures in the vinylation reaction are shown to be methoxide ion complexes with the alkali metal hydroxide and acetylene molecules. The formation of these complexes results in the activation of the acetylene molecule and an increase in the nucleophilicity of the methoxide ion. In the C₂H₂/CH₃OH/KOH/DMSO reaction system, a proton exchange between the acetylene molecule and the anionic nucleophile ([OH]^- and [CH₃O]^-) is freely performed with the formation of systems with ethynideions, whereas the thermodynamically preferable formation of vinyl alcohol or methyl vinyl ether is determined by a barrier of 20 kcal/mol.     

New reactions of alkynes with ketones in superbasic media

The present work reviews new reactions of alkynes with ketones in the superbasic media MOH—DMSO (M = Na, K, Cs) and KOBu^t—DMSO: the stereoselective nucleophilic addition of deprotonated ketones to the triple bond to form the E-isomers of β,γ-enones; vinylation of tertiary acetylenic alcohols that formed in situ from acetylene and ketones; the direct synthesis of vinyl ethers of tertiary acetylenic alcohols from acetylene and ketones; the stereoselective synthesis of dispirocyclic ketals containing the Z-ethylene fragment from arylalkynes and two molecules of a cyclic ketone; the stereoselective cascade synthesis of hexahydroazulenones from two arylalkyne molecules and 2-alkylcyclohexanones; the stereoselective cascade assembly of 7-methylidene-6,8-dioxabicyclo[3.2.1]octanes from two acetylene molecules and two ketone molecules; the stereoselective cascade synthesis of 7-methylidene-6,8-dioxabicyclo[3.2.1]octanes from acetylenes and 1,5-diketones; and the three-component cascade reaction of acetylene, ketones, and oximes to afford 4-methylidene-3-oxa-1-azabicyclo-[3.1.0]hexanes.     

<Emphasis Type="Italic">Ab initio</Emphasis> quantum-chemical study of vinylation of pyrrole and 2-phenylazopyrrole with acetylene in a KOH/DMSO system

Interaction between pyrrole and its 2-vinyl, 2-azo, and 2-phenylazo derivatives with acetylene in the gas phase and DMSO was studied using the MP2/6-311++G**//MP2/6-31G* ab initio approach and including the solvation effects within the framework of the continuum model. Possible reasons are considered for the hindered character of direct vinylation of azopyrroles with acetylene in superbasic media. The introduction of the azo group in the 2 position of the pyrrole ring leads to the increased stability of the pyrrole anion and increased acidity from pK _a = 22.1 for pyrrole and pK _a = 20.5 for vinylpyrrole to pK _a = 16.6 and 16.4 for 2-azopyrrole and 2-phenylazopyrrole, respectively. The binding energy between the pyrrole anion and the acetylene molecule decreases concurrently. The heat of formation of the pyrrole anion adducts with acetylene changes from ΔH = 4.8 kcal/mol for pyrrole to ΔH = 22.4 kcal/mol for 2-phenylazopyrrole. For all anion adducts under study, preferable isomers are Z isomers formed by the interaction of pyrrole anions with the cis-distorted acetylene molecule, but the formation of the E isomers corresponds to a lower activation barrier, which explains known Z stereoselectivity of the nucleophilic addition to monosubstituted acetylenes. When an azo group is introduced, the reaction becomes more endothermal, and the energy barriers to the formation of both Z and E isomers increase. Among other reasons for lowering of the activity of 2-arylazopyrroles during vinylation we consider possible reaction of acetylene addition at the most remote nitrogen atom of the azo group and participation of the anion center in cation chelation (K⁺ in the calculation).     

Direct vinylation of glucose derivatives with acetylene

Vinyl ethers, promising chiral carbohydrate synthons, have been synthesized by the addition of glucose acetals (1,2:5,6-di-O-isopropylidene-α-d-glucofuranose, methyl 4,6-O-benzylidene-α-d-glucopyranoside, 1,2-O-cyclohexylidene-α-d-glucofuranose, methyl α-d-glucopyranoside) to acetylene under atmospheric and elevated pressures in an autoclave in the presence of superbase catalytic systems (KOH-DMSO, t-BuOK-DMSO). The complete vinylation of 1,2:5,6-di-O-isopropylidene-α-d-glucofuranose and methyl α-d-glucopyranoside has been realized under elevated pressure of acetylene in the system KOH-THF as well.     

Reaction of indazole and alkylpyrazoles with acetylene

The reaction of indazole and pyrazole and its alkyl-substituted derivatives with acetylene was studied. It was established that indazole and 3(5)-methylpyrazole form a mixture of vinyl isomers corresponding to their tautomeric forms under vinylation conditions. The ratios of the isomers of vinylindazoles in the reaction mixtures depend on the nature of the catalyst. The indazole isomers were separated by gas-liquid chromatography, and the 3(5)-methylpyrazole isomers were separated by vacuum fractionation. 1-Di(1-pyrazolyl)ethanes, the structure of which was confirmed by their PMR spectra, are also formed in the vinylation of pyrazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1247–1251, September, 1976.     

Pyrroles from ketoximes and acetylene.

2-Aryl- and 1-viny1-2-pyrroles were synthesized by condensation of p-substituted acetophenone oximes with acetylene under pressure in superalkaline media (KOH/DMSO). The initially formed nitrogen-unsubstituted pyrroles can be vinylated in the presence of acetylene. Lithium hydroxide, which is completely inactive in the vinylation step, was found to be a selective catalyst for the construction of a pyrrole ring from oximes of aliphatic aromatic ketones. In the case of aliphatic and cycloaliphatic ketoximes (for example, cyclohexanone oxime) LiOH has virtually no catalytic effect on the reaction. The yields of 1-viny1-2-ary1-pyrroles depend substantially on the substituent in the phenyl ring. The structures of the synthesized compounds were confirmed by the IR, PMR, UV, and ¹³C NMR spectra.See [1] for communication II.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 489–491, April, 1978.     

Highly effective stereoselective synthesis of vinyl ethers of 5-alkyl-2-(2-furyl)-5-hydroxymethyl-1,3-dioxanes

The vinylation of cis-5-alkyl-5-hydroxymethyl-2-(2-furyl)-1,3-dioxanes in the KOH–DMSO system in acetylene at atmospheric or elevated pressures (85-100°C, 3 h) takes place stereoselectively and leads to the formation of cis-5-alkyl-2-(2-furyl)-5-vinyloxymethyl-1,3-dioxanes with yields of up to 93%.     

Nucleophilic Addition to Acetylenes in Superbasic Catalytic Systems: X. Catalytic Effect of Alkali Metal Hydroxides in the Vinylation of 1-Heptanol

The catalytic activity of alkali metal hydroxides in base-catalyzed addition of 1-heptanol to acetylene depends on the alkali metal nature and degree of hydration of its hydroxide. In a closed system, the catalytic activity of alkali metal hydroxides decreases in the series 2KOH·H₂O > RbOH·H₂O > CsOH·H₂O > NaOH. The corresponding series for a flow system is as follows: RbOH·H₂O > CsOH·H₂O > 2KOH·H₂O > NaON > KOH·H₂O. The difference is explained by participation of the catalyst in side reactions with both 1-heptanol and acetylene. Addition of dimethyl sulfoxide to the catalytic system accelerates the vinylation process.