V. V. Ershov

Synthesis of heterocyclic derivatives of 3,6-di-tert-butyl-o-benzoquinone by catalytic dehydrocondensation with ethylene glycol, glycerol, and diethanolamine

The dehydrocondensation of 3,6-di-tert-butyl-o-benzoquinone with ethylene glycol, glycerol, its chlorhydrin, and with diethanolamine, catalyzed by MnO2−NaOH, has been carried out in an alcohol-DMF medium with the formation of 7,10-di-tert-butyl-2,5-dioxabicyclo[4.4.0]deca-1,6-diene-8.9-dione, its 4-hydroxymethyl and 4-chloromethyl derivatives, and 7,10-di-tert-butyl-5-(β-hydroxyethyl)-2-oxa-5-azabicyclo[4.4.0]deca-1,6-diene-8,9-dione.

ESR study of products of transformation of 3,6-tert-butylpyrocatechol on alumina, zinca, silica, and titania

The formation of semiquinone and phenoxazyl radicals and metallocomplexes with semiquinone ligands was observed by ESR during the interaction of di-tert-butylpyrocatechol with Al2O3, ZnO, SiO2, and TiO2. In the case of different modifications of SiO2, admixtures of TiO2 exhibit a higher reactivity in complex formation with the organic substrate.

Hydroxylation of substituted diatomic phenols and their derivatives

Oxidation of 3,6-di-tert-butylpyrocatechol in protic media is accompanied by the formation of 3,6-di-tert-butyl-2-hydroxy-para-benzoquinone. Hydroxylation of the 3,5-isomer results in dealkylation and isomerization with the formation of 6-tert-butyl-2-hydroxy-para-benzoquinone and the quinone mentioned above, respectively. Their ratio depends on the nature of the solvent. Analogous processes accompany redox transformations of 2,6-di-tert-butylhydroquinone, 2,6-diphenyl-para-benzoquinone, and 2,4,6-tri-tert-butylphenol adsorbed on silica gel. Derivatives of 3,5-substituted pyrocatechols formed under conditions of heterophase oxidation in air are capable of transformations to form nitrogen-containing compounds.

SOLID-PHASE BROMINATION OF HINDERED PHENOLS

The solid-Phase bromination of a series oftert-butyl-substituted phenols withN-bromosuccinimide and dioxane dibromide afforded halogenated cyclohexadienones, quinobromides. Under the extrusion conditions, the latter underwent further transformations, mainly, debromination. A new reaction, dioxane dibromide catalyzed anhydroheterocyclization of 2,2′-dihydroxy-3,3′,5,5′-tetra-tert-butyldiphenyl to 2,4,6,8-tetra-tert-butyldibenzofuran, was discovered and the mechanism of this reaction was proposed.

Oxidation of 2-dialkylaminomethyl-4,6-di-tert-butylphenols

Oxidative transformations of 2-dialkylaminomethyl-4,6-di-tert-butylphenols depend on the nature of the oxidant, the character of the substituents at the nitrogen atom, and the medium. A mechanism of the oxidation of these compounds is suggested. The molecular structure of the compound obtained as a result of oxidative trimerization of 2-dimethylaminomethyl-4,6-di-tert-butylphenol was established by X-ray structural analysis.

Isotopic Study of the Formation of Phenoxazine Derivatives in the Transformations of 3,5-Di-tert-Butylcatechol Adsorbed in Thin SiO2-nTiO2 Layers in the Air

A study was carried out on the isotopic composition of the tetra-tert-butylphenoxazine derivatives formed in the heterophase transformations of 3,5-di-tert-butylcatechol adsorbed on thin SiO2 layers with microscopic traces of Ti and Mn in a nitrogen-oxygen atmosphere enriched with 15N2. The formation of isotopically-labeled tetra-tert-butylphenoxazinyl and hydroxytetra-tert-butylphenoxazinyl radicals and tetra-tert-butylphenoxazinone indicated the participation of atmospheric nitrogen in the heterophase catalytic reaction.

Solid-phase oxidation of 2,4-Di-tert-butylphenol and 3,6-Di-tert-butylpyrocatechol in the presence of alkali and alkaline earth metal halides under elastic deformation

Solid-phase oxidation of 2,4-di-tert-butylphenol to give 2,2′,4,4′-tert-butyl-6,6′-bisphenol and of 3,6-di-tert-butylpyrocatechol to afford 3,6-di-tert-butyl-l,2-benzoquinone was performed in the presence of alkali and alkaline earth metals halides under conditions of modified extrusion. The formation of the corresponding metal 3,6-di-tert-butylsemiquinolates was registered by ESR method. The different behavior of chlorides, bromides, and iodides was observed and rationalized basing on the dissimilar complexing ability of halogens. The mechanism of activated oxidation was assumed.

Reactivity in solid phase. Transformations of 2,4-di-tert-butylphenol and its derivatives under elastic deformation conditions

The solid-phase transformations of 2,4-di-tert-butylphenol (1) and its 6-bromo- (5) or 6-hydroxymetyl-substituted (11) derivatives were studied. The dependence of the behavior of compounds1 and5 in solid-phase processes on the composition of the medium was found. Oxidative coupling with the participation of atmospheric oxygen as an oxidant became possible at an excess of NaOH (or in NaOH/NaCl medium). The mechanism of oxidative debromocondensation of compound 5 that involves spontaneous dehalogenation of the haloquinolide intermediate and heterolysis of the C-Br bond with the elimination of Br+ was proposed. It was concluded that the mechanism proposed is common to solid-phase dienone-phenol transformations. The dual reactivity of compound11, determined by the chemical hardness of the anion-catalyst, was discovered.

The Free Radical Tautomerism

The phenomenon of different chemical groups migration between two oxygen atoms in di-tret-butyl-2-R-oxyphenoxy radicals was observed with the help of the ESR method, and the migration frequencies were measured.