L. M. Pokrovskii

Catalytic and Noncatalytic Ammonolysis of Chloropentafluorobenzene

Ammonolysis of chloropentafluorobenzene both in the presence and in the absence of copper(I) salt results mainly in replacement of the para- and ortho-fluorine atoms with respect to chlorine rather than replacement of the chlorine atom. Ammonolysis of 4-chloro-2,3,5,6-tetrafluoroaniline and 2-chloro-3,4,5,6-tetrafluoroaniline in the absence of copper(I) salt yields exclusively the corresponding fluorine substitution products, whereas in the presence of copper(I) salt the chlorine atom is replaced. Successive ammonolysis of chloropentafluorobenzene in the presence of copper catalyst along these two paths was put into the basis of a new method for preparation of 2,3,5,6-tetrafluoro-1,4-phenylenediamine.

Electrophilic Amination of Methylbenzenes with the System NaN3-AlCl3-HCl. Effects of the Solvent, Crown Ether, and Substrate Structure

Using mesitylene and o-xylene as examples, it was shown that the solvent nature strongly affects the conversion of methylbenzenes in electrophilic amination with the system NaN3-AlCl3-HCl. Two-parameter correlations were found between the substrate conversion, on the one hand, and dielectric constant and number of heavy atoms in the solvent, on the other. A considerable solvent effect on the regioselectivity of amination of o-xylene was observed. The presence of 18-crown-6 weakly affects the ratio of isomeric amines, but the conversion of o-xylene sharply decreases. Solid aromatic substrates, such as durene and pentamethylbenzene can also be involved in electrophilic amination with the system NaN3-AlCl3-HCl. On the basis of the experimental data and the results of quantum-chemical calculations, participation of a nitrenium intermediate in this reaction was postulated.

Catalytic and Noncatalytic Ammonolysis of Polyfluorinated 1,3-Dichlorobenzenes *

Reactions of 1,3-dichlorotetrafluorobenzene and 1,3-dichloro-2,4,6-trifluorobenzene with aqueous ammonia in the presence and in the absence of copper(I) salt lead to fluorine replacement by amino group in the para and ortho positions with respect to the chlorine atom. Ammonolysis of the resulting chloropolyfluoroanilines in the absence of a catalyst involves replacement of fluorine atom in the meta position with respect to the amino group. In the presence of copper(I) salt, catalytic aminodechlorination occurs at the para and ortho positions with respect to the amino group introduced in the first stage.

Mechanism of low-molecular alkenes interaction with sulfur-containing spatially hindered phenols under conditions of thermal modification of polymer materials

Transformations in the course of high-temperature modification of polyolefins under action of sulfur-containing modifiers have been studied using hexene-1 and hexane as model compounds. Composition of products of thermolysis of bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propyl] disulfide and bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propyl] sulfide at 200–270°C has been elucidated by means of thermogravimetry and gas chromatography-mass spectrometry. Mechanism of olefins modification with sulfides and disulfides involving the formation of biradical intermediates is discussed.

Replacement of an oxygen atom by chlorine atoms in the reaction of pentafluorobenzaldehyde with CCl3-substituted compounds in the presence of AlCl3

The interaction of pentafluorobenzaldehyde with RCCl3 (R = Cl, Ph, C6F5) in the presence of threefold molar excess of AlCl3 proceeds with replacing the oxygen atom of the aldehyde group by two chlorine atoms from the CCl3 group and results in the formation of pentafluorobenzylidene chloride. The electrophilic mechanism of the reaction is proposed.

Oxidative dimerization of 2,6-Di-tert-butyl-4-(2-hydroxyethyl)phenol

Abstract2,6-Di-tert-butyl-4-(2-hydroxyethyl)phenol undergoes oxidative self-coupling by the action of K3Fe(CN)6 in alkaline medium at room temperature to give 7,9-di-tert-butyl-4-(3,5-di-tert-butyl-4-hydroxyphenyl)-1-hydroxymethyl-2-oxaspiro[4.5]deca-6,9-dien-8-one. The composition of the reaction products has been determined, and the mechanism of their formation is discussed.

About selective methods of synthesis of 6-tert-butyl-2-methylphenol and 6-tert-butyl-2,4-dimethylphenol

Vapor phase catalytic methylation with methanol of 2-tert-butylphenol at the temperature 280–300°C proceeds selectively with formation of 6-tert-butyl-2-methylphenol. Elevating reaction temperature above 300°C leads to formation of 2,6-dimethylphenol. Reaction of 2-tert-butylphenol with methanol in alkaline medium in the presence of zinc oxide is shown to lead initially to formation of a mixture of calixarenes and methylenebisphenols that at elevated temperature exert splitting leading in future to 6-tert-butyl-2,4-dimethylphenol. Obtaining it in this reaction from 2,2′-methylenebis-(6-tert-butyl-4-methylphenol) proceeds selectively. Pathways of the reductive methylation of methylenebisphenols with methanol in alkaline medium is considered.

Development of a one-stage synthesis of 2,6-di-tert-4-ethylbutylphenol from 2,6-di-tert-butylphenol

Investigation of the catalyzed reaction of 2,6-di-tert-butylphenol with ethanol, ethylene glycol, oligomeric glycols, and paraldehyde in a strongly basic medium permitted to develop a technologically suitable procedure for manufacture of 2,6-di-tert-4-ethyl-butylphenol, used in the synthesis of Antioxidant-425.

Cyclocondensation of 1H-indol-2-amine with pentane-2,3,4-trione 3-arylhydrazones

Abstract3-(Aryldiazenyl)-2,4-dimethyl-9H-pyrido[2,3-b]indoles were synthesized for the first time by cyclocondensation of 1H-indol-2-amine with pentane-2,3,4-trione 3-arylhydrazones.

Oxidation of cyclohexene and α-pinene with O2—H2 mixture in the presence of supported platinum or palladium catalysts

Oxidation of cyclohexene and α-pinene with an O2—H2 mixture in the catalytic systems containing Pt or Pd and heteropoly compounds (HPC) was studied. The main oxidation products are epoxides, allyl alcohols, and ketones. The highest yield of the oxidation products was obtained in the presence of the platinum catalyst in combination with HPC PW11 or PW11Fe. The reaction mechanism was proposed. A relationship between the HPC composition and the nature of intermediates involved in oxidation was examined.