Effect of the nature of the cation in 2,6-di-tert-pentylphenolates on the kinetics and mechanism of the reaction of 2,6-di-tert-pentylphenol with methyl acrylate

The nature of the cation (K or Na) in 2,6-di-tert-pentylphenolates (ArOK or ArONa) affects the kinetics of the reaction of 2,6-di-tert-pentylphenol (ArOH) with methyl acrylate. This is associated with the ability of ArONa to replace the cation with a proton during interaction with methyl 3-(4-hydroxy-3,5-di-tert-pentylphenyl)propionate (HOArAlkOMe) to form a more efficient catalyst, sodium 4-(2-methoxycarbonylethyl)-2,6-di-tert-pentylphenolate (NaOArAlkOMe). Two different kinetic schemes, which describe the kinetics of the consumption of ArOH in the presence of ArOK and ArONa, are proposed. The elemental-stage rate constants are calculated by mathematical simulation of the reaction kinetics with consideration of the features of catalysis in the presence of ArOK and ArONa.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 827–830, May, 1994.     

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.     

Potassium and sodium 2,6-di-tert-butylphenoxides and their properties

The crucial factor of the reaction of 2,6-di-tert-butylphenol with alkali hydroxides is temperature, depending on which two types of potassium or sodium 2,6-di-tert-butylphenoxides are formed. These types exhibit different catalytic activity in the alkylation of 2,6-di-tert-butylphenol with methyl acrylate. More active forms of 2,6-Bu^t ₂C₆H₃OK or 2,6-Bu^t ₂C₆H₃ONa are synthesized at temperatures higher than 160 °C and are predominantly the monomers, which dimerize on cooling. The data of ¹H NMR, electronic, and IR spectra for the corresponding forms of 2,6-Bu^t ₂C₆H₃OK and 2,6-Bu^t ₂C₆H₃ONa isolated in the individual state are in agreement with cyclohexadienone structure. In DMSO or DMF, the dimeric forms of 2,6-di-tert-butylphenoxides react with methyl acrylate to form methyl 3-(4-hydroxy-3,5-di-tert-butylphenyl)propionate in 64–92% yield. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2138–2143, December, 2006.     

N-amination of 2,6-di-tert-butylpyridine

Summary Despite its low nucleophilicity 2,6-di-tert-butylpyridine (DTBP) easily undergoes N-amination. Other hidered pyridines react similarly. Comparison of the NMR carbon chemical shifts of 2,6-disubstituted 1-aminopyridinium perchlorates and those of the respective 1-methylpyridinium salts shows that the changes are parallel. 1-Amino-2,6-di-tert-butylpyridinium perchlorate does not react withp-dimethylaminobenzaldehyde. However, other hindered 1-(4-dimethylaminobenzylideneamino)pyridinium salts were obtained by a standard procedure.

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N-Aminierung von 2,6-di-tert-Butylpyridin

Zusammenfassung Trotz seiner geringen Nucleophilie ist an 2,6-Di-tert-butylpyridin (DTBP) leicht eine N-Aminierung durchzuführen. Andere gehinderte Pyridine reagieren ähnlich. Ein Vergleich der NMR-Kohlenstoffverschiebungen von 2,6-disubstituiertem 1-Aminopyridiniumperchlorat mit denjenigen der entsprechenden 1-Methylpyridiniumsalze zeigt, daß die Änderungen parallel verlaufen. 1-Amino-2,6-di-tert-butylpyridiniumperchlorat reagiert nicht mitp-Dimethylaminobenzaldehyd, hingegen wurden andere gehinderte 1-(4-Dimethlylaminobenzylidenamino)pyridiniumsalze über Standardmethoden erhalten.

     

The reaction of 3,6-di-tert-butyl-1,2-benzoquinone and 3,6-di-tert-butylcatechol withtert-butyl hydroperoxide

Reaction of 3,6-di-tert-butyl-1,2-benzoquinone and 3,6-di-tert-butylcatechol withtert-butyl hydroperoxide in aprotic solvents leads to the generation of semiquinone (SQ^.H), alkylperoxy (ROO^.), and alkyloxy radicals. The reaction of SQ^.H and ROO^. produces 2,5-di-tert-butyl-6-hydroxy-1,4-benzoquinone, 3,6-di-tert-butyl-1-oxacyclohepta-3,5-diene-2,7-dione, and 2,5-di-tert-butyl-3,6-dihydroxy-1,4-benzoquinone. The radical generated from solvent attacks SQ^.H at position 4 with C−C bond formation. 4-Benzyl-2,5-di-tert-butyl-6-hydroxycyclohexa-2,5-diene-1-dione produced in this way is transformed into 4-benzyl-3,6-di-tert-butyl-1,2-benzoquinone under the reaction conditions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 943–946, May, 1999.     

Thermal decomposition of 2,6-di-tert-butyl-4-dimethylaminomethylphenol

Products of thermolysis of 2,6-di-tert-butyl-4-dimethylaminomethylphenol were determined qualitatively and quantitatively by GLC, UV, and¹H NMR methods. The kinetics of the reaction was studied. The thermolysis products were studied as the inhibitors in thermopolymerization of monomers. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1881–1883, October, 1997.     

Kinetic study of the protolysis of 2,6-di-tert-butyl-4-hydroxyphenoxyl

The kinetic acidity of 2,6-di-tert-butyl-4-hydroxyphenoxyl in tetrahydrofuran has been estimated by means of ESR. It is shown that ion pairs are formed in the process of proton transfer from the radical to triethylamine.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2512–2516, November, 1992.     

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.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1499–1503, June, 1996.     

Interaction of functionally-substituted 4-alkyl-2,6-di-<Emphasis Type="Italic">tert</Emphasis>-butylphenols with hydrohalic acids

Reactions of 4-alkyl-2,6-di-tert-butylphenols containing OH, SH, COOH, and COOMe groups in their para substituents with hydrogen chloride and hydrohalic acids were studied. One-step transformations of 2,6-di-tert-butyl-4-(ω-hydroxyalkyl)phenols to the corresponding 4-(ω-halogenoalkyl)phenols, as well as of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and its esters to phloretic acid were proposed. 4-(3-Mercaptopropyl)phenol upon heating with conc. HBr undergoes condensation to 3-(4-hydroxyphenyl)propyl 4-(3-mercaptopropyl)phenyl sulfide as the main product. Dedicated to the memory of Academician N. N. Vorozhtsov on the 100th anniversary of his birth. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1078–1083, June, 2007.     

HY Zeolite Modified by Liquid Silane Deposition and Its Catalytic Activity in Selective tert-Butylation of Naphthalene

HY zeolites were modified by chemical liquid deposition with i-C₄H₉Si(OC₂H₅)₃, followed by hydrothermal treatment. The samples were characterized by X-ray diffraction, N₂ adsorption and pulse mass analysis to investigate the influence on framework structure, specific surface area, pore diameter and adsorption behaviors. The catalytic performances of HY zeolite and the modified samples in the alkylation of naphthalene with tert-butyl alcohol were also evaluated. The results showed the modification of HY zeolite did not change framework structure but increased specific surface area, decreased average pore diameter, and reduced the size of pore opening. Catalytic activity of the modified HY zeolite catalyst for tert-butylation of naphthalene was decreased compared with that of HY zeolite catalyst while shape-selectivity of 2,6-di-tert-butylnaphthalene (2,6-DTBN) was increased obviously, the highest 2,6-DTBN/2,7-DTBN ratio of 6.62 obtained.     

Kinetics and mechanism of the reaction of ozone with 3,6-di-tert-butylpyrocatechol

The reaction of ozone with 3,6-di-tert-butylpyrocatechol at 20°C was investigated, and it was found that the main reaction product was 3,6-di-tert-butylquinone, while the reaction rate was proportional to the concentrations of the reagents. A reaction scheme explaining the mechanism of formation of the main and side products is proposed.N. N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, 117977 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 6, pp. 1443–1447, June, 1992.     

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. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1328–1335, July, 1997.     

Structures of oxidation products of 4,6-di-tert-butylpyrogallol

Oxidation of 4,6-di-tert-butylpyrogallol gave two dimeric products instead of the expected 4,6-di-tert-butyl-3-hydroxy-1,2-benzoquinone (2). It was established by X-ray diffraction analysis that the first product has the structure of tetra-tert-butyl-6, 10a-dihydroxy-1,2-dioxo-3,4a,7,9-1,2,4a, 10a-tetrahydrodibenzo-1,4-dioxine. From this it follows that compound 2 undergoes regio- and stereospecific dimerization according to the [2π+4π]-cycloaddition mechanism,viz, the hetero Diels—Alder reaction. The double intensities of the signals in the¹H NMR spectrum are indicative of a symmetrical structure of the second product, 2,6,4′, 6′-tetra-tert-butyl-4,4′-dihyroxy-3,5,3′,5′-tetraoxo-4,4′-bi(cyclohexene), which is a racemate of enantiomers formed upon recombination (r+r orl+l) of the intermediate of oxidation of pyrogallol, namely, of ther,l-stereogenic 3,5-di-tert-butyl-1-hydroxy-2,6-dioxocyclohex-3-enyl radical. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 139–146, January, 1999.     

ESR study of the effect of water on the kinetics of proton transfer and exchange in solutions of semiquinone radicals

The interaction of 3,6-di-tert-butyl-2-hydroxyphenoxyl with triethylamine in the reaction of proton transfer is catalyzed by water. However, the rate of proton exchange with diethylamine is independent of water admixtures in the reaction medium. ESR showed that the complexing of 3,6-di-tert-butyl-2-hydroxyphenoxyl with water leads to redistribution of the spin density.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1018–1021, June, 1994.     

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.     

Some laws governing the alkylation of 6-tert-butyl-2-methylphenol with methyl acrylate in the presence of a phenoxide

A kinetic scheme of the reaction between 6-tert-butyl-2-methylphenol and methyl acrylate in the presence of an alkali metal phenoxide has been proposed. The rate constants of the elementary steps describing the catalytic mechanism have been calculated. The reaction gives methyl 3-(5-tert-butyl-4-hydroxy-3-methylphenyl)propionate as the only product (Calkylation). The nature of the metal cation does not affect the reaction mechanism.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 504–507, March, 1993.     

Kinetics of proton exchange between semiquinone radicals and NH-acids

Using EPR the proton exchange between 3,6-di-tert-butyl-2-oxyphenoxyl, 4-triphenylmethyl-6-tert-butyl-3-chloro-2-hydroxyphenoxyl, and secondary amines was studied. The nature of the solvent had no effect on the kinetic parameters of the process which was attributed to the formation of strong complexes owing to ring type hydrogen bonds. The effect of prototropy on the mechanism of proton exchange was examined.A. I. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, pp. 2505–2511, November, 1992.     

Investigation of radical pairs produced upon pulse action of elastic waves on the 3,6-di-tert-butylcatechol-3,6-di-tert-butyl-o-benzoquinone-sulfur system

The pulse action of elastic waves on polycrystalline mixtures of 3,6-di-tert-butylcatechol and 3,6-di-tert-butyl-o-benzoquinone produces radical pairs stable at room temperature, and the addition of polycrystalline sulfur considerably increases their yield. The dependences of formation and decay rates of paramagnetic centers on the composition of the mixture were studied. The threshold character of formation of paramagnetic centers at various powers of elastic wave pulse was established.Translated fromIzvestiya Akademii Nauk. Seriva Khimicheskaya, No. 4, pp. 864–868, April, 1996.     

Possibility of applying the electrochemical version of the Horner reaction to the synthesis of unsaturated lactones

Direct electrochemical reduction of specially synthesized 2-[(diethoxyphosphorylacetoxy] benzaldehyde on a platinum electrode in an aprotic medium is accompanied by ester bond cleavage, and not formation of coumarin via the phosphonate-anion followed by intramolecular Horner cyclization. This could be realized, as a matter of principle, in the presence of an ionol anion (2,6-di-tert-butyl-4-methylphenoxide), electrochemically generatedin situ.Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 144–146, January, 1993.     

Reactions of poly(methyl methacrylate) radicals with some <Emphasis Type="Italic">p</Emphasis>-quinones in the presence of tri-<Emphasis Type="Italic">n</Emphasis>-butylboron in methyl methacrylate polymerization

The polymerization of methyl methacrylate initiated by dicyclohexyl peroxydicarbonate at 30 °C was studied in the presence of tri-n-butylboron and a series of quinones, namely, p-benzoquinone, chloranil, and 2,5-di-tert-butyl-p-benzoquinone, whose concentration changed from 0.25 to 2.00 mol.%. The initial polymerization rate and molecular weight of poly(methyl methacrylate) depend on the structure and concentration of quinone. The growth radicals react with p-benzoquinone and chloranil predominantly at the C=C bond, while they react at the C=O bond of 2,5-di-tert-butyl-p-benzoquinone. The terminal stable oxygen-centered radicals that formed react with alkylborane, terminating reaction chains and generating alkyl radicals into the bulk. The latter are involved in chain initiation.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2114–2119, October, 2004.