Development of a one-stage synthesis of 2,6-di-<Emphasis Type="Italic">tert</Emphasis>-4-ethylbutylphenol from 2,6-di-<Emphasis Type="Italic">tert</Emphasis>-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.     

Alkylation of 2,6-di-<Emphasis Type="Italic">tert</Emphasis>-butylphenol with methyl acrylate catalyzed by potassium 2,6-di-<Emphasis Type="Italic">tert</Emphasis>-butylphenoxide

The kinetics of catalytic alkylation of 2,6-di-tert-butylphenol (ArOH) with methyl acrylate (MA) in the presence of potassium 2,6-di-tert-butylphenoxide (ArOK) depends on the method for the preparation of ArOK. The reaction of ArOH with KOH at temperatures > 180 °C affords monomeric ArOK, whose properties differ from those in the case of potassium 2,6-di-tert-butylphenoxide synthesized by the earlier methods. The regularities of ArOH alkylation depend on the ArOK concentration, the ArOH: MA ratio, and the effect of microadditives of polar solvents. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1971–1974, October, 2007.     

Extraction-spectrophtometric determination of vanadium using 2,6-dithiol-4-<Emphasis Type="Italic">tert</Emphasis>-butylphenol and aminophenols

Mixed-ligand complexes of vanadium(II, IV, V) with 2,6-dithiol-4-tert-butylphenol and aminophenols have been studied by spectrophotometry. Extraction of mixed-ligand complexes is maximal at pH 1.2–4.8. The optimal conditions for the formation and extraction of mixed-ligand compounds have been found and the ratios of components in the complexes have been determined. A procedure has been developed for extraction-spectrophotometric determination of vanadium in soils.     

Inhibiting activity of isocamphyl substituted phenols and their mixtures with 2,6-di-<Emphasis Type="Italic">tert</Emphasis>-butylphenol in the initiated oxidation of ethylbenzene

The stoichiometric coefficients of inhibition and rate constants for the reaction of several terpenephenols (isocamphyl substituted phenols) with ethylbenzene peroxy radicals were measured. Their reactivity was found to increase as the number of alkyl substituents grew and decreased with an o-alkoxyl compared with o-alkyl substituent because of the formation of an intramolecular H-bond. In spite of similar antiradical activities of terpenephenols with isocamphyl and isobornyl substituents, the reactivities of phenoxyl radicals formed from them in the interaction with sterically hindered phenol molecules are substantially different. They are higher for isocamphylphenols with substituents turned with respect to the aromatic ring plane.     

Urotropin synthesis of 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butylsalicylic acid derivatives

The stability of 3,5-di-tert-butylsalicylic aldehyde against oxidation is due to autoinhibiting of the chain process. However its oxidation into 3,5-di-tert-butylsalicylic acid was performed at the use of acetyl protection of the hydroxy group. In reaction of 6-bromo-2,4-di-tert-butylphenol with urotropin the formation was discovered of 3,5-di-tert-butylsalicylic acid, its nitrile and amide.     

Heterospin biradicals based on new piperidineoxyl-substituted 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o</Emphasis>-benzoquinone

A nucleophilic addition reaction of 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (OH-TEMPO) to 3,6-di-tert-butyl-o-benzoquinone was used to obtain a new sterically hindered o-benzoquinone (1) containing 2,2,6,6-tetramethylpiperidineoxyl functional group, which was characterized by IR spectroscopy, mass spectrometry, elemental analysis, and X-ray diffraction. A one-electron reduction of 1 with potassium and thallium is an efficient method for the generation of earlier unknown heterospin biradicals 5a and 5b, respectively, containing nitroxide and o-semiquinone radical centers. Analysis of the hyperfine structure of the ESR spectra of biradicals 5a and 5b in solution showed that they belong to the group of heterospin biradicals with strong (J >> a) and fast exchange interaction between the radical centers.     

Geometrical and energetical aspects of structure of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o-</Emphasis>benzoquinones

From the geometrical point of view, all observed conformations of the 3,6-di-tert-butyl-o-benzoquinone fragments are determined by the inequivalent positions of the Me groups of the tBu substitutes relative to the carbonyl oxygen atoms. The geometrical inequivalence is believed to cause the energetic inequivalence of the Me groups. The relevant quantum mechanical computations revealed intramolecular contacts of the C=O···H-(tBu)-type (2.37–3.83 kcal/mole) that can be interpreted to be hydrogen bonding interactions.     

Mono-<Emphasis Type="Italic">meso</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylporphyrin

Summary. Treatment of meso-tetra(tert-butyl)porphyrin with sulfuric acid/n-butanol affords a mixture of porphyrin and mono-tert-butylporphyrin in relatively high yield.     

Physicochemical study of new polydentane ligand systems based on 2,6-diformyl-4-<Emphasis Type="Italic">tert</Emphasis>-butylphenol

New polydentate ligand systems, products of condensation of 2,6-diformyl-4-tert-butylphenol with 1,3-diaminopropanol-2 and carbo(thiocarbo)hydrazide, were synthesized and their structure was determined based on the data of elemental analysis, ¹H NMR and IR spectroscopy. The acid-base properties of bisazomethine I have been studied. Spatial structure and spectral properties of the ligand system were simulated using quantum-chemical calculations.     

Synthesis and photochemical properties of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-9<Emphasis Type="Italic">H</Emphasis>-carbazole derivatives

Method of synthesis has been developed for a series of 3,6-di-tert-butyl-9H-carbazole derivatives and their photochemical properties have been investigated. The dependence of the Steglich esterification reaction on the nature of the catalyst was studied. The synthesized compounds show fluorescent emission in the range 400–600 nm with a high quantum yield.     

Alkaline hydrolysis of diethyl <Emphasis Type="Italic">N</Emphasis>-acetylamino(3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxybenzyl)malonate

Alkaline hydrolysis of diethyl N-acetylamino(3,5-di-tert-butyl-4-hydroxybenzyl)malonate is accompanied by decarboxylation. The efficiency of this process depends on the temperature and ratio of the reactants. A possibility of tautomerism with migration of the proton of phenolic hydroxyl and the influence of the structure on the antioxidation properties were considered on the basis of analysis of the IR spectral data and quantum chemical (PM6) calculation of the structures. The energies of homolysis of the O-H bond of phenolic hydroxyl were calculated for a series of the synthesized compounds. It is proposed to predict the antioxidation activity on the basis of these values.     

Binuclear nickel(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butylbenzoate and 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxybenzoate anions and 2,3-lutidine: the synthesis,structure, and magnetic properties

Two novel binuclear nickel(II) complexes [Ni₂(O₂CR)₄(2,3-lut)₂] (O₂CR is anion of 3,5-di(tert-butyl)benzoic acid (bzo, 1) and 4-hydroxy-3,5-di(tert-butyl)benzoic acid (hbzo, 2); 2,3-lut is 2,3-lutidine) with four carboxylate bridges were synthesized. The structure of complex 1 was determined by X-ray diffraction. Both dimers 1 and 2 were characterized by elemental analysis, IR spectroscopy, and magnetic measurements. The presence of the α-substituent in the apical lutidine ligand leads to a distortion of the geometry of the metal carboxylate core in complex 1 as a result of short steric contacts Me(Lut)…O(OOCR) (3.134(7) Å). This is apparently responsible for a considerable decrease in the exchange parameters of complexes 1 and 2 (J =–30.0 and–23.6 cm^–1, respectively) as compared to known analogues. Density functional calculations of the structure and magnetic properties of 1 and 2 were carried out by the UB3LYP/6-31G(d,p) method.     

2,6-diformyl-4-<Emphasis Type="Italic">tert</Emphasis>-butylphenol bis-ferrocenoylhydrazone and binuclear copper(II) complexes on its basis

2,6-Diformyl-4-tert-butylphenol bis-ferrocenoylhydrazone (1, H₃L) and binuclear copper(II) complexes on its basis [Cu₂(H₂L)(OH)] (2), [Cu₂(H₂L)Cl₃]·(3), and [Cu₂(H₂L)(OH)]·₂NO₃ (4) have been synthesized and investigated. Tautomerism of bis-hydrazone (1) has been studied.     

Chlorination of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-1,2-benzoquinone in two-phase catalytic system

Chlorination of 3,6-di-tert-butyl-1,2-benzoquinone in a two-phase catalytic system (CH₂Cl₂, HCl- H₂O, H₂O₂, Bu₄NCl) led to halogen addition at the C=C bond, and subsequent dehydrochlorination of the adduct gave 3,6-di-tert-butyl-4-chloro-1,2-benzoquinone. Chlorination of the latter afforded 3,6-di-tert-butyl-4,5-dichloro-1,2-benzoquinone.     

Reactions of 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-1,2-benzoquinone with mercapto carboxylic acids

Heating of an equimolar mixture of 3,5-di-tert-butyl-1,2-benzoquinone with thiosalicylic acid led to 2-[(4,6-di-tert-butyl-2,3-dihydroxyphenyl)thio]benzoic acid. In the case of β-mercaptopropionic acid, 2-[(4,6-di-tert-butyl-2,3-dihydroxyphenyl)thio]propionic acid was formed, which upon reflux in Ac2O was converted to 6,8-di-tert-butyl-9-hydroxy-3,4-dihydro-2H-1,5benzoxathiepin-2-one.     

Interaction of 9-substituted anthracenes with oxidation systems <Emphasis Type="Italic">tert</Emphasis>-butylhydroperoxide-metal <Emphasis Type="Italic">tert</Emphasis>-butoxide

9-R-Anthracenes (R = Me, Ph) are effective acceptors of peroxyl and metalalkoxyl radicals in the systems tert-butylhydroperoxide-metal tert-butoxide (M = Al, V, Cr; C₆H₆, 20°C). Isolation of 9-R-9,10-dihydro-9,10-di-tert-butylperoxyanthracenes, 10-R-10-tert-butylperoxy-9-anthrones as major products reliably confirms the formation of tert-butylperoxy radicals and can be used for quantitative assessment of their content.     

Titanium tetra-<Emphasis Type="Italic">tert</Emphasis>-butoxide-<Emphasis Type="Italic">tert</Emphasis>-butyl hydroperoxide oxidizing system: Physicochemical and chemical aspects

The reaction of titanium tetra-tert-butoxide with tert-butyl hydroperoxide (1: 2) (C₆H₆, 20 C) involves the steps of formation of the titanium-containing peroxide (t-BuO)₃TiOOBu-t and peroxytrioxide (t-BuO)₃TiOOOBu-t. The latter decomposes with the release of oxygen, often in the singlet form, and also homolytically with cleavage of both peroxy bonds. The corresponding alkoxy and peroxy radicals were identified by ESR using spin traps. The title system oxidizes organic substrates under mild conditions. Depending on the substrate structure, the active oxidant species can be titanium-containing peroxide, peroxytrioxide, and oxygen generated by the system.     

Reactions of benzazole-2-thiones with 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxybenzyl acetate

The benzylation of benzothiazole(oxazole, imidazole)-2-thiones with 3,5-di-tert-butyl-4-hydroxybenzyl acetate involves either the sulfur or nitrogen atom depending on the reaction conditions. The S- and N-benzylation products of benzazole-2-thiones are kinetically and thermodynamically controlled products, respectively. The use of 3,5-di-tert-butyl-4-hydroxy-benzyl acetate allows sterically hindered hydroxybenzyl derivatives of benzаzole-2-thiones to be generally synthesized under milder conditions than in known methods of their synthesis.     

Inhibitory effect of 2,6-di-<Emphasis Type="Italic">tert</Emphasis>-butylphenol groups in iron and manganese porphyrins on the catalytic activity in the oxidation of hydrocarbons by hydrogen peroxide

Iron and manganese porphyrins containing 2,6-di-tert-butylphenyl groups (R₄PFeCl and R₄PMnCl) have been synthesized to be further immobilized on silica gels via various spacers. The activity of these porphyrins in the oxidation of alkanes and alkenes by hydrogen peroxide has been studied. 2,6-Di-tert-butylphenol groups decrease the catalytic activity of porphyrins in oxidation processes.     

Antistress properties of sodium 1-<Emphasis Type="Italic">N</Emphasis>-acetylamino-1-carboxy-2-(3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxyphenyl)propionate

The effect of a spatially-hindered phenol, namely sodium 1-N-acetylamino-1-carboxy-2-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, on the functionality of mitochondria of rat liver was studied. Stress impact caused a 3 to 4-fold increase in the fluorescence intensity of the products of lipid peroxidation (LPO) in the membranes of these organelles. The preparation reduced the intensity of LPO to the control level, which was conductive to maintaining high functional activity of the mitochondria. Prevention of mitochondrial dysfunction was probably associated with an increase in the resistance of animals to stress factors.