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.     

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.     

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.     

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.     

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.     

Inclusion of nickel(<Emphasis Type="SmallCaps">II</Emphasis>) and copper(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with aliphatic polyamines in cucurbit[8]uril

The inclusion compound of macrocyclic cavitand cucurbit[8]uril (CB[8]) with the nickel(II) complex containing the tetraazamacrocyclic ligand cyclam, {[Ni(cyclam)]@CB[8]}Cl₂··16H₂O (1), and the inclusion compounds of CB[8] with the copper(II) bis-ethylene-diamine complex, {trans-[Cu(en)₂(H₂O)₂]@CB[8]}Cl₂·{CB[8]}·42H₂O (2a) and {trans-[Cu(en)₂(H₂O)₂]@CB[8]}Cl₂·17H₂O (2b), were synthesized and characterized by X-ray diffraction analysis, IR and ESR spectroscopy, and electrospray mass spectrometry. Guest—host inclusion compounds can be directly synthesized starting from a metal complex and cucurbit[8]uril, as was exemplified by the preparation of compounds 2a and 2b.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2414–2419, November, 2004.     

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.     

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.     

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.     

Synthesis and studies of spectroscopic and electrochemical properties of dinuclear ruthenium(<Emphasis Type="SmallCaps">II</Emphasis>) and manganese(<Emphasis Type="SmallCaps">II</Emphasis>) complexes

New dinuclear ruthenium manganese complexes of general composition (bpy)₂Ru(L)MnCl_x(H₂O)₂ (L is 1,10-phenanthroline-5,6-dione, 3,3′-dicarboxy-2,2′-bipyridyl, or bis(pyrazolyl); x = 2 or 4) were synthesized by the reaction of (bpy)₂Ru(L) with MnCl₂ · 4H₂O. These compounds and the starting mononuclear ruthenium complexes were studied by spectrophotometric and electrochemical methods in MeCN. The position of the charge-transfer band Ru^II → L in the spectra depends on the donor-acceptor characteristics of the ligand L. For the dinuclear complex under study, the formal potentials of reversible one-electron oxidation of Ru^II are in the range of 0.9–1.2 V (vs. the standard hydrogen electrode), whereas oxidation of Mn^II occurs at more positive (by 0.1–0.2 V) potentials. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2281–2285, October, 2005.     

Synthesis and some properties of tetrakis-3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxybenzylated calix[4]resorcinols

A method for the synthesis of new calix[4]resorcinols tetra-3,5-di-tert-butyl-4-hydroxybenzyl derivatives is developed. Their interaction with methyldichlorophosphonate, dimethyldichlorosilane in the presence of a base leads to formation of organophosphorus-organosilicon cavitands. Acetylation of hydroxybenzylated calix[4]resorcinols with acetic anhydride leads to products of either incomplete or full acetylation depending on experimental conditions.     

Synthesis and crystal structure of 5-(3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxyphenyl)-1,2,3,5-tetrahydrophenazine

5-(3,5-Di-tert-butyl-4-hydroxyphenyl)-1,2,3,5-tetrahydrophenazine was synthesized by the reaction of 2,6-di-tert-butyl-1,4-benzoquinone-4-(o-aminophenyl)imine with cyclohexanone. The structure of the reaction product was established by X-ray diffraction.     

New tin(<Emphasis Type="SmallCaps">iv</Emphasis>) <Emphasis Type="Italic">o</Emphasis>-iminosemiquinone complexes

New tin(iv) mono- and bis-o-iminosemiquinone complexes were obtained by the exchange reaction of radical anion lithium salt of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-imino-benzoquinone with tin(iv) organochlorides. The compounds synthesized were characterized by EPR spectroscopy and X-ray diffraction analysis. Substituents on the tin atom were found to affect stability of paramagnetic metal derivatives formed.     

Alkoxylation of 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-1,2-benzoquinone. New bis-1,2-benzoquinones

Alkoxylation of 3,6-di-tert-butyl-1,2-benzoquinone with a number of diols, including propane-1,3-diol, butane-1,4-diol, di-, and triethylene glycols, and cyclohexane-1,4-diyldimethanol, was studied. Nine new 4-alkoxy-3,6-di-tert-butyl-1,2-benzoquinones were synthesized, four of which were bis-1,2-benzoquinones with different tethers (6–13 atoms) between the quinone fragments. Depending on the length of the chain between the hydroxy groups in glycols, bicyclic 4,5-disubstituted 3,6-di-tert-butyl-1,2-benzoquinones were formed or their stepwise alkoxylation occurred. The newly synthesized o-benzoquinone derivatives can be reduced with alkali metals to give radical anions and converted into semiquinone chelates with manganese carbonyl.     

About selective methods of synthesis of 6-<Emphasis Type="Italic">tert</Emphasis>-butyl-2-methylphenol and 6-<Emphasis Type="Italic">tert</Emphasis>-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.     

Synthesis of substituted 3,4-dihydropyrimidin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones and pyrimidin-2(1<Emphasis Type="Italic">H</Emphasis>)-ones by the Biginelli reaction with 3,5-Di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4-hydroxybenzaldehyde

Three-component acid-catalyzed cyclocondensation of 3,5-di-tret-butyl-4-hydroxybenzaldehyde with urea and ethyl acetoacetate or α-nitroacetophenone (Biginelli reaction) under homogeneous conditions gave the corresponding 5-substituted 3,4-dihydropyrimidin-2(1H)-ones having in position 4 of the heteroring an aryl substituent with sterically shielded hydroxy group. The condensation catalyzed by inorganic salts (Fe³⁺, Co²⁺, Zn²⁺, Li⁺) was successful only with ethyl acetoacetate as initial methylene-active component. Under analogous conditions, acetophenone and 4-fluoroacetophenone gave rise to 4,6-diarylpyrimidin-2(1H)-ones which are capable of undergoing phenol-quinonemethide tautomerism.     

Anionic condensations of 3,5-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-4(2)-hydroxybenzaldehydes in the presence of weak bases

Products of the reactions of 4- and 2-hydroxy-3,5-di-tert-butyl-benzaldehydes with malonic acid, diethyl malonate, and acetic anhydride in the presence of weak bases were isolated and identified. The reactions of 3,5-di-tert-butyl-4-hydroxybenzaldehyde with malonic acid and acetic anhydride in the presence of sodium acetate and piperidine gave 3,5-di-tert-butyl-4-hydroxycinnamic acid. The reaction of its 2-hydroxy isomer with acetic anhydride stopped at the stage of formation of the corresponding O-acetyl derivative, while in the reaction with malonic acid the corresponding substituted cinnamic acid and its lactone (coumarin derivative) were formed as intermediate products in a transformation sequence finally leading to 3-(3,5-di-tertbutyl-2-hydroxyphenyl)-3-piperidinopropionic acid and 6,8-di-tert-butyl-2-oxo-3,4-dihydro-2H-chromen-4-ylacetic acid. Analogous differences were typical of reactions of isomeric 4- and 2-hydroxy-3,5-di-tert-butylbenzaldehydes with diethyl malonate. The transformations of the 2-hydroxy isomer were accompanied by hydrolysis and formation of an adduct of intermediate coumarin derivative with diethyl malonate and piperidine.     

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.     

Novel diphenylsulfimide antioxidants containing 2,6-di-<Emphasis Type="Italic">tert</Emphasis>-butylphenol moieties

New diphenylsulfimide derivatives containing substituents with the 2,6-di-tert-butylphenol moiety at the nitrogen atom were synthesized. Their molecular structures were established by X-ray diffraction. Antioxidant activity was experimentally evaluated by spectrophotometry based on hydrogen transfer to the stable radicals, namely, 2,2-diphenyl-1-picrylhydrazyl and the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS^·+), and using in vitro lipid peroxidation in rat brain and liver homogenates. The presence of phenol and diphenylsulfimide moieties in one molecule leads to a significant enhancement of antioxidant activity. The new compounds exhibit moderate inhibitory activity against enzymes involved in carbohydrate and lipid metabolism. The evaluation of antiglycation activity showed that the new sulfimides taken at a concentration of 100 μmol L^–1 have activity comparable with that of aminoguanidine.     

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.