L. I. Larina

Synthesis of 1,3-Dialkylimidazolium and 1,3-Dialkylbenzimidazolium Salts

A number of N-alkylimidazoles and N-alkylbenzimidazoles were synthesized by reactions of imidazole and benzimidazole with alkyl halides. The reaction rate increases by a factor of 2 to 3 under conditions of microwave activation. Subsequent treatment of the resulting N-alkylazoles with alkyl halides afforded the corresponding 1,3-dialkylimidazolium and 1,3-dialkylbenzimidazolium halides.

New Synthesis and Properties of 3-Alkyl-, 3-Chloroalkyl-, 3-Perfluoroalkyl-, and 3-Aryl-1-methyl-(5-halo)pyrazoles from Chloro(bromo)vinyl Ketones and N,N-Dimethylhydrazine

A new regioselective heterocyclization was revealed in the reaction of 2-chloro- and 2,2-dichloro(bromo)vinyl ketones with N,N-dimethylhydrazine to afford 3-substituted 1-methyl(5-halo)pyrazoles. The reaction is accompanied by elimination of methyl halide and formation of up to 90% of N,N,N-trimethylhydrazinium halide as the second product.

NMR investigation of chlorophosphorylation products of N‐vinylazoles

The structure of novel phosphorus‐containing N‐vinylazoles prepared by action of phosphorus pentachloride has been studied by multinuclear 1H, 13C, 15N, 31P and two‐dimensional (2D) NMR spectroscopy. N‐vinyl‐substituted 1,2‐diazoles and 1,2,3‐triazoles have undergone phosphorylation, exclusively, on double bond. N‐vinylazoles‐based hexa‐coordinated phosphorus compounds have been synthesized for the first time. 31P NMR spectroscopy provides the most convenient and unambiguous method for the investigation of E—Z‐isomeric structures of phosphorylated enamines. Copyright

1H, 13C and 15N NMR spectroscopy and tautomerism of nitrobenzotriazoles.

Benzotriazole nitro derivatives were prepared by nitration of the corresponding benzotriazoles and by methylation or cyclization of appropriate nitro‐1,2‐phenylenediamines. Structures and tautomerism of the nitrobenzotriazoles were studied by multinuclear 1H, 13C, 15N, and 2D NMR spectroscopy and quantum chemistry. Copyright

Reactions of stereoselective addition of selenium dibromide and monobromide to acetylene

The reaction of selenium tetrabromide with acetylene afforded bis(2-bromovinyl)selenium dibromide as a mixture of isomers [1]. No information existed on the reaction of selenium dibromide and monobromude with acetylene. We perform systematic research on the reactions of selenium halides with unsaturated compounds [2–12]. It was shown for the first time in [2, 3] that selenium dichloride and dibromide were suitable for the preparation of organoselenium compounds. By the addition of selenium dichloride and dibromide to divinyl sulfide, diorganyldiethynylsilanes and –germanes new heterocyclic compounds were synthesized [2–12]. We performed for the first time the reactions of selenium dibromide and monobromide with acetylene. They proceed as a stereoselective anti-addition with the formation of a previously unknown E,E-bis(2bromovinyl)-selenide (I) in 90–98% yield. of selenium monobromide with acetylene in chloroform at 30–40°C resulted in selenide I in 98% yield (calculated on the taken selenium monobromide) and was accompanied by the elemination of elemental selenium. The reactions were characterized by high stereoselectivity: exclusively compound of the E,E-configuration was obtained. This stereoslectivity might originate from the involvement into the reaction cyclic intermediates A, B. The formation of analogous intermediates in the reactions of electrophilic addition of compounds with a selenium–halogen bond to alkynes was previously established [13].

Configurational Assignment and Conformational Study of Methylglyoxal Bisdimethylhydrazones Derived from the 2-Ethoxypropenal Precursor

A configurational assignment of the isomeric methylglyoxal bisdimethylhydrazones derived from the 2-ethoxypropenal precursor has been performed based on experimental measurements and high-level ab initio calculations of 1J(C,C) and 1J(C,H) couplings. The results reveal the marked stereochemical dependence upon the orientation of the lone pairs of both nitrogen atoms in different isomers. Methylglyoxal bisdimethylhydrazone is shown to exist in a mixture of the EE and ZE isomers (ca. 75:25), both of which adopt predominant s-trans conformations with minor (up to 8°) out-of-plane deviations.

1,3-dipolar cycloaddition of trimethylsilyl azide to propynals and dimerization of 1H-1,2,3-triazole-5-carbaldehydes to tricyclic bis-hemiaminals

Reactions of trimethylsilyl azide with 3-trimethylsilyl-2-propynal and 2-propynal were studied. X-Ray analysis of the molecular structure of 4-trimethylsilyl-1H-1,2,3-triazole-5-carbaldehyde showed that the carbonyl group appears in the s-cis conformation with respect to the double C=C bond in the heteroring. The effect of the temperature and polarity of the medium on the ability of 1H-1,2,3-triazole-5-carbaldehyde to undergo dimerization to tricyclic bis-hemiaminals was examined by IR and 1H NMR spectroscopy.

Synthesis, structure, and characteristics of 1,2-dichlorovinyl alkyl ketones

A method of alkyl 1,2-dichlorovinyl ketones preparation from acyl halides and 1,2-dichloroethylene was developed. The configurational equilibrium and electronic structure of alkyl 1,2-dichlorovinyl ketones was investigated by IR, 1H and 13C NMR spectroscopy, by measuring dipole moments, and by quantum-chemical calculations using methods RHF and B3LYP in the basis 6–311++G (d,p). Alkyl 1,2-dichlorovinyl ketones are stable in the Z, s-cis-configuration where the olefin proton is involved into an intramolecular hydrogen bond with the oxygen of the carbonyl group. Reaction of 1,2-dichlorovinyl ketones with alkylhydrazines afforded 1-alkyl-3-alkyl-4-chloropyrazoles. The reaction of alkyl 1,2-dichlorovinyl ketones with 1,1-dimethylhydrazine involved dehydrochlorination and afforded 1,1-dimethylhydrazinium hydrochloride and a mixture of compounds with uncertain structure.

Chloro(bromo)vinyl ketones and 2,2-Dichloroacrolein in Reactions with Hydrazines

Reactions of 2,2-dichlorovinyl and 2,2-dibromovinyl ketones with alkylhydrazines afford respectively 1-R-3-alkyl(aryl)-5-chloro- or 5-bromopyrazoles in preparative yields. The dichloroacrolein forms with alkylhydrazines and dimethylhydrazine only the corresponding hydrazones. Quantum-chemical calculations were performed characterizing the structure of the obtained ketones and dichloroacrolein alkylhydrazones, of dichloroacrolein dimethylhydrazone, of 1-alkyl-5-chloropyrazolinium halides, and 1-alkyl-5-chloropyrazoles.

Universal method for trimethylsilylation of acetylenic alcohols and glycols

Abstract A highly convenient universal method for trimethylsilylation of acetylenic alcohols and glycols via treatment by hexamethyldisilazane in the presence of benzoic acid sulphimide as a catalyst has been developed. The rate of trimethylsilylation of acetylenic alcohols is reduced from primary to secondary and to tertiary alcohols accordingly, as well as with the decreasing of hydroxyl nucleophylicity. The toxicity of trimethylsilyl acetylenic ethers, except 2-trimethylsiloxy-3-butyne, is much lower than that of original compounds.