Pyrroles from ketoximes and acetylene. 11. Conformation of 1-vinylpyrroles from1H NMR data

A number of 1-vinylpyrroles were studied by PMR spectroscopy. Bulky substituents in the position of the pyrrole ring give rise to deshielding of h_b and a decrease in²J(H_A,H_B) and⁶J(H₃,H_B). The results were interpreted as a decrease in the p, conjugation in the N-vinyl group due to distortion of the coplanarity. The dihedral angle () between the planes of the pyrrole ring and the double bond was estimated (with an accuracy of ±5 °).See [10] for our previous communication [10].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 328–330, March, 1980     

<Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR Study of Bifurcated Intramolecular Hydrogen Bonds in 2,6-Bis(2-pyrrolyl)pyridine and 2,6-Bis(1-vinyl-2-pyrrolyl)pyridine

According to the ¹H and ¹³C NMR data, bifurcated intramolecular hydrogen bond NH?N?HN in 2,6-bis(2-pyrrolyl)pyridine fixes its molecule in a conformation with syn orientation of the pyrrole rings. An analogous bifurcated hydrogen bond CH?N?HC is formed in 2,6-bis(1-vinyl-2-pyrrolyl)pyridine. 2-(1-Vinyl-2-pyrrolyl)-6-(2-pyrrolyl)pyridine is characterized by unsymmetrical bifurcated hydrogen bond NH? N?HC.     

Arrays of Nonselective Nonionic-Surfactant Sensors for the Separate Determination of the Homologues of Polyoxyethylated Nonylphenols

It was demonstrated that multisensor systems of the electronic tongue type based on nonselective solid-contact potentiometric sensors can be used for the separate determination of the homologues of nonionic surfactants— polyoxyethylated nonylphenols with different numbers of oxyethyl groups. The cross-sensitivity parameters were calculated for modified and unmodified sensors for nonionic surfactants. The artificial neural network method was used for processing analytical signals.__________Translated from Zhurnal Analiticheskoi Khimii, Vol. 60, No. 6, 2005, pp. 646–653.Original Russian Text Copyright © 2005 by Mikhaleva, Kulapina.Presented at the VI All-Russian Conference (with International Participation) on Electrochemical Methods of Analysis (EMA-2004, Ufa, May 23–27, 2004).     

Ethynylation of pyrroles with 1-acyl-2-bromoacetylenes on alumina: a formal ‘inverse Sonogashira coupling’

Pyrroles are cross-coupled with 1-acyl-2-bromoacetylenes on the surface of Al₂O₃ at room temperature under solvent-free conditions to afford 2-(acylethynyl)pyrroles with 100% regioselectivity and in good yields, thus representing the first example of a palladium-, copper-, base-, and solvent-free (‘green’) ethynylation of pyrroles, which can be considered a formal ‘inverse Sonogashira coupling’. Given the interest in functionalized pyrroles and acetylenes, this new facile and environmentally friendly cross-coupling should be of significant interest for the role of acylhaloacetylenes in pyrrole and acetylene chemistry.     

Annelation of the Pyrrole to the Steroid Skeleton Using the Trofimov Reaction

The product of annelation of the N-vinyl pyrrole ring with steroid skeleton of 5-cholestene was obtained in a single regioselective step by the reaction of 5-cholesten-3-one oxime with acetylene in KOH-DMSO by the Trofimov reaction.     

Synthesis of polyacetylene with sulfoxide functions

Polyacetylene functionalized by sulfoxide groups was synthesized from poly(methyl vinyl sulfoxide) by the elimination of methanesulfenic acid under the action of a strong base at 20—50 °C.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 774–776, March, 2005.     

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.     

Synthesis and liquid crystal properties of substituted 5-(arylcarbonyloxy)-2(p-cyanophenyl)pyrimidines

Liquid crystal p-substituted benzoates, biphenylcarboxylates, and benzoyloxybenzoates were obtained on the basis of 5-hydroxy-2-(p-cyanophenyl)pyrimidine. The development of nematogenicity by the esters due to the p-cyanophenyl grouping was noted, and the appearance of the smectic mesophase by the variation of the ring framework of the acid fragment of the molecule was investigated.Novosibirsk Institute of Organic Chemistry, Siberian Branch of the Russian Academy of Sciences (RAN), Novosibirsk 630090. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 371–376, March, 1995. Original article submitted December 19, 1994.     

5-Alkoxy-2-(p-cyanophenyl)pyrimidines: New lowmelting liquid crystals

The C₄-C₈ homologues of new, stable, low-melting pyrimidine liquid crystals of the 5-alkoxy-2-(p-cyanophenyl)pyrimidine series have been synthesized. Their liquid-crystal properties have been studied, and it has been shown that the C₄-C₆ homologues manifest nematic properties, while the C₇ and C₈ homologues have a smectic mesophase along with the nematic mesophase.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 206–208, February, 1993.     

New examples of the vinylation of NH-heterocycles with acetylene at atmospheric pressure in the KOH-DMSO system

Vinylation of 2-hetarylpyrroles, 4,5-dihydrobenzo[g]indole, and 1,2,3,4-tetrahydro--carbinols at atmospheric pressure in the superbasic system KOH-DMSO at 100–120 ° C has given the corresponding N-vinyl derivatives in yields of 92–99%.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 481–485, April, 1986.