Chemistry of O-Benzoquinones and Masked O-Benzoquinones I. Diels-Alder Reactions of O-Benzoquinones with Dimethyl Acetylenedicarboxylate and Phenylacetylene

Diels-Alder reactions of six o-benzoquinones with dimethyl acetylenedicarboxylate has been examined. The yields of adducts vary with the natures of the o-benzoquinones, 3,4-Di-n-propyl-(1c), 3,6-di-n-propyl (1d). 3. 4-diallyl-(1e) and 3, 6-diallyl-o-benzoquinone (1f) are found to give bicyclic a-diketones exclusively without the formation of 1,4-dioxine derivatives, the yields ranging from 20 to 70%. In the case of 4, 5-dimethoxy-o-benzoquinone, dimethyl 4, 5-dimethoxyphthalate is produced in 42% yield, presumably derived from the decomposition of the corresponding initially formed α-diketone. 3, 6-Di-n-propyl-4, 5-dimethoxy-o-benzoquinone deteriorates without addition to dimethyl acetylenedicarboxylate upon heating. The additions of o-benzoquinones 1c , 1d and 1f to phenylacetylene are also studied. The yields of adducts, α-diketones, range from 23% to 82%.     

Hypervalent and binuclear silicon and germanium derivatives from bis-(3,5-di-tert-butyl-2-phenol)-oxamide

The reactions of bis-(3,5-di-tert-butyl-2-phenol)oxamide (1) with Cl₂SiR₂ (Me or Ph) or Cl₂GeR₂ (Me, nBu or Ph) in THF provided binuclear pentacoordinated silicon and germanium compounds: bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylsilane (2), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenylsilane (3), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-dimethylgermane (4), bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-di-n-butylgermane (5) and bis-(3,5-di-tert-butyl-2-oxo-phenyl)-oxamido-bis-diphenylgermane (6). The mono-nuclear tetracoordinated silicon compounds N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(dimethylsilane) (8) and N-acetyl-bis-(3,5-di-tert-butyl-2-oxo-phenyl)-amide-bis-(diphenylsilane) (9) were synthesized from N-(3,5-di-tert-butyl-2-phenol)acetamide (7) and Cl₂SiR₂ (R = Me and Ph). Comparison of the ²⁹Si NMR chemical shifts of the penta- (2 and 3) and tetracoordinated (8 and 9) silicon compounds provided information about the intramolecular coordination of the carbonyl group to the silicon atom. Compounds 3 and 6 were characterized by single-crystal X-ray analyses. They have planar hexacyclic structures where the central atoms present distorted tbp geometries with one nitrogen and two carbon atoms in equatorial positions and two oxygen atoms in apical positions.     

Lithium-silylindolide als Precursor für 1,2-, 1,3-Bis(silyl)indole und Bis(indol-1,3-yl)silane

Lithium-silylindolide as Precursor of 1,2-, 1,3-Bis(silyl)indoles and Bis(indole-1,3-yl)silane Lithium-indolide reacts with difluorosilanes (F₂SiR₂: R = CHMe₂ ( 1 ); CMe₃ ( 2 )) in a molar ratio 2 : 1 with formation of bis(indole-1-yl)silanes. The 1-(di-tert-butylfluorosilyl)-3-(fluorodiisopropylsilyl)indole ( 3 ) is obtained in the reaction 1-(di-tert-butylfluorosilyl)-3-lithium-indolide and F₂Si(CHMe₂)₂. In a molar ratio 2 : 1 the bis(1-di-tert-butylfluorosilyl-indole-3-yl)diisopropylsilane 4 is formed. As a byproduct bis(1-di-tert-butylfluorosilyl-indole-3-yl)dimethylmethane ( 5 ) is isolated. A cleavage of THF and the formation of (indole-1-yl)diisopropylvinyloxysilan ( 6 ) occurs in the reaction of 1-diisopropylfluorosilylindole with t-BuLi in THF. 1-(di-tert-butylfluorosilyl)indole reacts with n-BuLi/TMEDA accompanied by an 1,2-anionic silyl group migration to give the 2-(di-tert-butylfluorosilyl)-1-lithiumindolide 7 . Hydrolysis of 7 gives the 2-(di-tert-butylfluorosilyl)indole ( 8 ). In the reaction of 7 with F₂Si(CHMe₂)₂ the 1-(diisopropylfluorosilyl)-2-(di-tert-butylfluorosilyl)indole 9 is obtained. 1-n-Butyl-diisopropylsilylindole ( 10 ) is the product of the reaction of F₂Si(CHMe₂)₂, n-BuLi/TMEDA and indole at –70 °C. Lithium-indolide reacts with 3 to give the 1-(di-tert-butylfluorosilyl)indole-3-yl)(indole-1-yl)-diisopropylsilane ( 11 ), the first example of this class of substances. In the reaction of 1 , F₂SiMe₂, and t-BuLi in THF the 1-(diisopropyl(indole-1-yl)silyl)-3-dimethyl-(3.3-dimethylbutylsilyl)indole 12 is isolated. The crystal structures of 2 , 5 and 9 are discussed.     

A new procedure for fusion of a five-membered ring. Building up of the naphtho[1,8-<Emphasis Type="Italic">bc</Emphasis>]furan system

Reactions of 2,6-di-tert-butylnaphthalene-1,5-diol with aminals derived from aromatic aldehydes afforded 2-aryl-4,8-di-tert-butyl-2H-naphtho[1,8-bc]furan-5-ols and 2-aryl-4,8-di-tert-butylnaphtho[1,8-bc]-furan-5-ones.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 9, 2004, pp. 1349–1351.Original Russian Text Copyright © 2004 by Tyurin, Minyaeva, Mezheritskii.     

Steric effects on forming different by-products in the formylation reaction of 2,4-dialkylphenol (dialkyl = t-Bu/t-Bu, t-Bu/Me and Me/Me) proved by their structural and spectral characterizations

In the formylation reaction of 2,4-dialkylphenol (2,4-di-tert-butylphenol, 2-tert-butyl-4-methylphenol and 2,4-dimethylphenol) in the presence of hexamethylenetetramine, steric effects of alkyl groups play important roles in forming different types of by-products, namely 2,4-di-tert-butyl-6-[(6,8-di-tert-butyl-2H-1,3-benzoxazin-3(4H)-yl)methyl]phenol (1), 2-tert-butyl-4-methyl-6-[(6-tert-butyl-8-methyl-2H-1,3-benzoxazin-3(4H)-yl)methyl]phenol (2) and tris(2-hydroxy-3,5-dimethylbenzyl)amine hydrochlorate (3). These three compounds are fully characterized and single-crystal structures of 1 and 3 are further elucidated.     

Synthesis and X-ray single crystal structure of first aromatic ortho-di-tert-butyl azolo[1,2,4]triazine

Oxidation of 3,4-di-tert-butyl-8-methyl-1,4-dihydropyrazolo[5,1-c][1,2,4]triazine with NBS/K₂CO₃ furnished 3,4-di-tert-butyl-8-methylpyrazolo[5,1-c][1,2,4]triazine, a mildly strained heteroaromatic compound. X-Ray single crystal diffraction analysis indicated that the conjugated 1,2,4-triazine ring adopts a twist-boat configuration, while the two t-Bu substituents are located on the opposite sides of the azole plane. The related 3-tert-butyl-4-(o-C-carboranyl)-8-methyl-1,4-dihydropyrazolo[5,1-c][1,2,4]triazine was also synthesized, however, its oxidative aromatization was unsuccessful.     

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.     

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.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 5, 2005, pp. 718–721.Original Russian Text Copyright © 2005 by Belostotskaya, Komissarova, Prokof’eva, Kurkovskaya, Vol’eva.     

Synthesis and structure of 2,4-di-tert-butyl-1-chloro-6-methyltricyclo[4.1.0.02,7]hept-4-en-3-one

The reaction of 2,6-di-tert-butyl-4-dichloromethyl-4-methylcyclohexa-2,5-dien-1-one with (Me₃Si)₂NNa yielded 2,4-di-tert-butyl-1-chloro-6-methyltricyclo[4.1.0.0^2,7]hept-4-en-3-one (substituted tropovalene). The structure of the title compound was established by¹H and¹³C NMR spectroscopy and X-ray diffraction analysis. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1642–1645, September, 1997.     

Reactions of lithium phenylacetylenide and lithium 3,3-dimethylbut-1-ynide with 3,6-di-tert-butyl-1,2-benzoquinone. Molecular structure of 2,5-di-tert-butyl-8-(3,6-di-tert-butyl-1,2-benzoquinon-4-yl)-8-phenylocta-2,4,6,7-tetraen-1,6-olide

Reactions of 3,6-di-tert-butyl-1,2-benzoquinone with PhC≡CLi and Bu^tC≡CLi are multistage processes. In the first stage, nucleophilic 1,2-addition of the organometallic compound too-benzoquinone occurs to form the corresponding hydroxycyclohexadienone derivative. In polar solvents, the latter undergoes rearrangement through insertion of the oxygen atom into the ring to form a new allenic organolithium compound. The reaction of the newly formed organometallic compound with the initialo-quinone occurs either as a one-electron transfer to yield lithium semiquinolate and a dimerization product,viz., 4,4′-bi(2,5-di-tert-butyl-9,9-dimethyldeca-2,5-dien-7-yn-1,6-olide), or as the 1,4-addition to yield 2,5-di-tert-butyl-8-(3,6-di-tert-butyl-1,2-benzoquinon-4-yl)-8-phenylocta-2,4,6,7-tetraen-1,6-olide. The structure of the latter compound was established by X-ray diffraction analysis and by NMR and IR spectroscopy. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 351–356, February, 1999.     

Synthesis of new ordered aromatic polyester copolymers

Aromatic polyesters of 3,5-di-tert-butyl-4-hydroxybenzoic acid and 3,5-diisopropyl-4-hydroxybenzoic acid were prepared. The polymers were found to be high-melting but largely insoluble in organic solvents. The polymer based on 3,5-di-tert-butyl-4-hydroxy-benzoic acid was not degraded to monomer by sulfuric acid. A number of new aromatic polyesters were also prepared. Several new monomers for aromatic polyesters were synthesized, including bis(2,5-di-tert-butyl-4-carbophenoxyphenyl)terephthalate, m- and p-phenylene bis(3,5-di-tert-butyl-4-hydroxybenzoate), bis(2,6-di-tert-butyl-4-chlorocarboxyphenyl)terephthalate, and m-phenylene bis(3,5-diisopropyl-4-hydroxybenzoate). An aromatic polyester prepared from bis(2,6-di-tert-butyl-4-chlorocarboxyphenyl) terephthalate and resorcinol had a η_inh (trichloroethylene) of 1.05 (0.5%, 30°C) and a possible melting point of 330°C (DSC). Tough, creasable films could be cast from trichloroethylene solution of this polymer. Attempts to observe or to trap the keto-ketene that might result when 3,5-di-tert-butyl-4-hydroxybenzoyl chloride is treated with base were unsuccessful.     

Synthesis of aromatic tetracyclic tin compounds by template and transmetallation reactions: Alkyl vs aryl migration from tin to nitrogen

The syntheses of [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]diphenyltin (1) and [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]dichloro-phenyl-stannate (2) by template reactions using 3,5-di-tert-butylcatechol, aqueous ammonia and SnPh₂Cl₂ are reported. We also report the syntheses of compounds 2, [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]trichloro-stannate (4), [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)methylamine]chloro-methyltin (5), and [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)-n-butylamine]n-butyl-chlorotin (6) and [bis(3,5-di-tert-butyl-2-hydroxy-2-phenyl)amine]n-butyl-dichloro-stannate (7), performed by transmetallation reactions of the octahedral zinc coordination compound Zn[3,5-di-tert-butyl-1,2-quinone-(3,5-di-tert-butyl-2-hydroxy-1-phenyl)imine]₂ (3) with SnPhCl₃ or SnPh₂Cl₂, SnCl₄, SnMe₂Cl₂, Sn(nBu)₂Cl₂ and Sn(nBu)Cl₃, respectively. The X-ray diffraction structures of compounds 1, 2, 4 and 6 are reported. The transmetallation reactions with Sn(alkyl)₂Cl₂ afforded pentacoordinated tin compounds, where an alkyl group migrated from tin to nitrogen, while similar reactions with Sn-Ph compounds did not present any phenyl group migration.     

The Synthesis of (3,5-DI-tert-butyl-4-hydroxyphenyl)methyl-(3-pyridylalkyl)-ethers via 1-(3,5-Di-tert-butyl-4-hydroxyphenyl)methyl Pyridinium Salts.

The rearrangement of 1-(3,5-di-tert-butyl-4-hydroxyphenyl)methyl pyridinium salts under basic conditions is described. A method for the synthesis of (3,5-di-tert-butyl-4-hydroxyphenyl)methyl-(3-pyridylalkyl)-ethers is elaborated.     

Synthesis of magnesium catecholate and <Emphasis Type="Italic">o</Emphasis>-semiquinone complexes by oxidation of the metal with 3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl-<Emphasis Type="Italic">o</Emphasis>-benzoquinone

Oxidation of amalgamated magnesium metal with 3,6-di-tert-butyl-o-benzoquinone (1) in different aprotic organic solvents afforded magnesium catecholate and bis-o-semiquinolate complexes. The catecholate derivatives of magnesium CatMgL₂ (Cat is the 3,6-di-tert-butyl-o-benzoquinone dianion, L = THF or Py) were synthesized in high yields in pyridine and tetrahydrofuran, respectively. The reactions in diethyl ether or dimethoxyethane produced hexacoordinated metal bis-o-semiquinolates SQ₂MgL_n (SQ is the 3,6-di-tert-butyl-o-benzoquinone radical anion, L = Et₂O, n = 2; L = DME, n = 1). The reaction with the use of toluene as the solvent gave a magnesium bis-o-semiquinolate complex containing the coordinated unreduced o-quinone molecule. The molecular structures of the [CatMgPy₂]₂ and SQ₂Mg·DME complexes were established by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 92–98, January, 2007.     

[4+2]-Cycloaddition of sterically hindered thiophene S-oxides to alkenes and SO extrusion reactions of the cycloadducts

Cycloaddition reactions of 2,5-di-tert-butylthiophene S-oxide and 2,3,4,5-tetrakis(p-tolyl)thiophene S-oxide with alkenes are described. The reactivity of 2,5-di-tert-butylthiophene S-oxide as diene in Diels–Alder reactions is compared with 2,5-di-tert-butylthiophene S,S-dioxide. The thermal and photochemical SO extrusion reactions of the cycloadducts under formation of highly substitutedaromatic compounds are exemplified.     

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. The study was carried out under financial support of the Russian Foundation for Basic Research (grant no. 96-03-33253a). Deceased.     

Alkylation of pyrocatechol in <Emphasis Type="Italic">tert</Emphasis>-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.     

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.     

Synthesis,structure and antioxidant activity of sulfur-containing tetrakisphenol

3-[2-(3,5-Di-tert-butyl-4-hydroxyphenylsulfanyl)acetoxy]2,2-bis[2-(3,5-di-tert-butyl-4-hydroxyphenylsulfanyl) acetoxymethyl]propyl 3,5-di-tert-butyl-4-hydroxyphenylsulfanylacetate was synthesized. Its structure was determined by means of ¹H and ¹³C NMR spectroscopy and X-ray-diffraction analysis. This compound was found to possess high antioxidant activity in the conditions of auto-oxidation of low-pressure polyethylene.     

Kinetics of the formation and dissociation of complexes of cobalt(II) with <Emphasis Type="Italic">meso</Emphasis>-Phenylocta(methyl)porphyrin derivatives in organic solvents

The influence of the deformation of the tetrapyrrole aromatic macrocycle and the electronic effects of substituents on the kinetic parameters in the formation and dissociation reactions of cobalt complexes of porphyrins are discussed on the basis of a study of the kinetics of the formation and dissociation of cobalt complexes with meso-phenyl octa(methyl)porphyrin derivatives: 5,10,15-triphehyl octa(methyl) porphyrin; 5,15-bis-(3′,5′-di-tert-butyl phenyl) octa(methyl)porphyrin; 5,10,15-tris-(3′,5′-di-tert-butyl phenyl) octa(methyl)porphyrin; and 5,10,15,20-tetrakis-(3′,5′-di-tert-butyl phenyl) octa(methyl)porphyrin in acetic acid and pyridine.