I. S. Belostotskaya

New Opportunities for Duff Reaction

Reaction of 2,4-di-tert-butylphenol with urotropin in conditions of Duff reaction takes an abnormal route and instead of the expected di-tert-butylsalicylaldehyde provides a mixture of N-substituted 3,5-di-tert-butyl-2-hydroxybenzylamines and redox conjugate benzoxazines containing mostly 6,8-di-tert-butyl-3-(3,5-di-tert-butyl-2-hydroxybenzyl)-2H-3,4-dihydrobenz[e][1,3]oxazine. A solvolysis of an individual benzoxazine in the system HO(CH2)2OH-H2O-HCl affords di(3,5-di-tert-butyl-2-hydroxybenzyl)amine, and in AcOH 3,5-di-tert-butylsalicilaldehyde. A mechanism of Duff reaction was suggested involving the formation of a benzoxazine intermediate.

New approach to the synthesis of 1,3-dioxolanes

Application of ethanol to the synthesis of 1,3-dioxolanes by the condensation of carbonyl compounds with vicinal diols results in a high yield of the reaction product and considerably reduces the duration of the process. It is assumed that the effect of the ethanol is caused by the adduct formation with carbonyl compounds (hemiacetals) which behave as active intermediates of the condensation. A cyclic ketal of acetone with glycerol obtained with the help of ethanol was used as a basis component in the synthesis of a series of ketals substituting diol or carbonyl components by transketalyzation mechanism proceeding without water liberation.

Structural factors responsible for the activity of macromolecular phenolic antioxidants

Hybrid macromolecular antioxidants based on hydrophilic polymers with chemically grafted sterically hindered phenol fragments in aqueous solution exhibited considerably higher antiradical activity than that typical of compositions consisting of a polymer and low-molecular phenol analogs. The activity of the examined antioxidants is determined mainly by formation of supramolecular structures in solution, as well as by the position of the phenolic fragment inside or outside hydrate shell. An important structural factor is the size of the spacer connecting the redox-active phenol ring with the polymer.

Photooxygenolysis of 3,6-di-tert-butyl-o-benzoquinone

The photolysis of 3,6-and 3,5-di-tert-butyl-o-benzoquinones in benzene (λ > 380 nm, inert atmosphere) involves decarbonylation of the compounds to furnish respectively 2,5-and 2,4-di-tert-butylcyclopentadienones. The 2,5-isomer is stable, and the 2,4-di-tert-butylcyclopentadienone suffers a conversion into a Diels-Alder adduct. The participation of oxygen inhibited the decarbonylation and changed the direction of the photolysis: Here the products of the 3,5-di-tert-butyl-o-benzoquinones conversion were a di-tert-butylmuconic anhydride and dipivalylethylene. It was concluded that a singlet oxygen was involved in the process which formed by a triplet-triplet annihilation at the interaction of 3O2 with a triplet-excited initial quinone.

1H NMR Study of Quaternization of 2,4-Di-tert-butyl-6-dimethylaminomethylphenol

The possibility was revealed for exhaustive protonation of 2,4-di-tert-butyl-6-dimethylaminomethylphenol with participation of lone electron pairs on both nitrogen and oxygen atoms. The reaction of the title compound with alkyl halides includes concurrent and consecutive processes leading to formation of the corresponding hydrohalides and quaternization products. The latter undergo spontaneous oxidation with atmospheric oxygen to give quaternary 6,8-di-tert-butyl-3-methyl-2H-3,4-dihydro-1,3-benzoxazine derivatives which were detected by 1H NMR spectroscopy.

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.

ANTIBACTERIAL ACTIVITY OF SUBSTITUTED 1,3-DIOXOLANES

Cyclic ketals and acetals (1,3-dioxolanes) substituted at positions 2 and 4 of the dioxolane ring, prepared by condensation of glycerol and ethylene glycol with aldehydes and ketones, had antimicrobial activity against Gram-positive and Gram-negative bacteria. This activity, which may be associated with the antiradical activity of the study compounds and depended on their hydrophilic-hydrophobic balance, allows targeted variation in structural parameters for the creation of new active compounds. Cyclic ketals with high antimicrobial activity can be used as antiseptics for sterilization of working surfaces and instruments.

Alkylation of pyrocatechol in tert-butyl alcohol-sulfuric acid-benzene

Alkylation of pyrocatechol with tert-butyl alcohol in benzene in the presence of sulfuric acid gave 3,5-di-tert-butylbenzene-1,2-diol in a higher yield than in analogous reaction with tert-butyl alcohol. This result was rationalized by reduction of inhibitory effect of liberated water, formation of heterogeneous system, and occurrence of the alkylation process in nonpolar organic phase. Intermediate products were identified and found to undergo intra- and intermolecular tert-butyl group transfer with formation of more stable 3,5-di-tertbutylbenzene-1,2-diol. The formation of p-di-tert-butylbenzene indicated participation of benzene in crossalkylation processes.