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.     

A study of the mechanism of photocrosslinking polymers by quinones

Photocrosslinking of poly(methyl methacrylate) (PMMA) was studied in the solid state in the presence of various quinones. For the study of photocrosslinking mechanism, a PMMA film containing p-benzoquinone (Q) was irradiated with UV light (λ > 370nm) and then purified by reprecipitation. It was found that the reprecipitated polymer has quinone-type moieties, besides the hydroquinone-type moieties, chemically bound to the polymer chain. The reprecipitated polymer film also crosslinking efficiency was higher than that of PMMA film containing Q. It was concluded that the formation of quinone-type structure during irradiation played an important role in the photocrossing of PMMA containing Q.     

Low-temperature oxidation of 3,6-di-tert-butyl-o-benzoquinone and 3,6-di-tert-butylpyrocatechol with tert-butyl hydroperoxide in the presence of aluminum, titanium, and zirconium tert-butylates

Systems consisting of metal (Al, Ti, Zr) tert-butylate and tert-butyl hydroperoxide oxidize 3,6-di-tert-butyl-o-benzoquinone under mild conditions (room temperature, benzene). With (t-BuO)₃Al and (t-BuO)₄Zr, the major reaction products are 5-hydroxy-3,6-di-tert-butyl-2,3-epoxy-p-benzoquinone, and with (t-BuO)₄Ti, 2-hydroxy-3,6-di-tert-butyl-p-benzoquinone. Under the conditions of this reaction, 3,6-di-tert-butylpyrocatechol initially transforms into 3,6-di-tert-butyl-o-benzoquinone. The reactions involve metalcontaining peroxides.     

Uncontrolled pseudoliving free-radical polymerization of methyl methacrylate in the presence of butyl-<Emphasis Type="Italic">p</Emphasis>-benzoquinones

Polymerization of methyl methacrylate initiated by dicyclohexyl peroxydicarbonate in the presence of tri-n-butylboron and butyl-p-benzoquinone or 2,5-di-tert-butyl-p-benzoquinone occurred with no induction period. The yields and molecular masses of the polymers linearly increased with an increase in the conversion degree, which suggests the free-radical mechanism of “living” chain polymerization. The poly(methyl methacrylate) macrochains of the prepolymers contained sterically hindered aromatic structures with labile C-O bonds. The latter underwent reversible homolytic dissociation to give a growth-inducing radical and sterically hindered aryloxyls. Pseudoliving free-radical polymerization in the presence of the prepolymer (macroinitiator) was studied at 45, 60, and 80 °C. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1119–1122, June, 2007.     

Polymerization of methyl methacrylate in the presence of 2,5-di-tert-butyl-p-benzoquinone

Polymerization of methyl methacrylate in the presence of 2,5-di-tert-butyl-p-benzoquinone is a combination of two processes: inhibited and controlled radical polymerization. The adduct of chain propagation radicals and p-quinone formed due to the inhibited polymerization is a macroinitiator of controlled radical polymerization. The fraction of the pseudo-living process is determined by the concentration of p-quinone in the starting polymerized composition. Post-polymerization proceeds via the reversible inhibition mechanism.

     

Catalytic Activity of Polymer Anchored Cu-tren Complex in the Oxidation of 2,6-Di-t-butyl Phenol

Poly(styrene-co-dimethylaminoethyl methacrylate) and poly(methyl methacrylate-co- dimethylaminoethyl methacrylate) were prepared by solution polymerization. These polymers were quaternized by methyl iodide and n-hexyl bromide. The produced polymers were used as support in the aqueous oxidation of 2,6-di-tert-butylphenol (DBP) using hydrogen peroxide catalyzed by tris(2-aminoethyl)amine copper(II) complex “Cu(II)-tren complex” anchored on the prepared polymers. The products obtained from the reactions were 3,3′-5,5′-tetra-tert-butyldiphenoquinine (DPQ) and 2,6-di-tert-butyl-p-benzoquinone (BQ). No reaction products were obtained when the reaction was carried out in the absence of polymeric catalyst. The polymer composition and reaction medium greatly affect product distribution of the reaction. Polar organic solvent like DMF and methanol favor the formation of DPQ, while nonploar organic solvent like benzene and methylene chloride favor the formation of BQ. Hydrophobic branches of polymers 6 (PS-HexBr-Cu-TREN) and 8 (PMMA-HexBr-Cu-TREN) favor BQ formation as the weight of support increased. On the other hand, DPQ is favored in the presence of hydrophilic branches as observed for both polymeric catalysts 5 (PS-MeI-Cu-TREN) and 7 (PMMA-MeI-Cu-TREN).     

Reactions of quinones with organometallic compounds: correlation analysis of substituent effects

The effects of substituents in lithium, magnesium, zinc, and cadmium organometallic compounds in their reactions with p-benzoquinone and 3,6-di-tert-butyl-o-benzoquinone on the ratio of addition and reduction products were considered. The reduction of quinones follows a homolytic mechanism of single electron transfer. The results of correlation analysis confirmed a suggestion that the addition to quinones followed a nucleophilic (heterolytic) mechanism.     

Synthesis of sterically hindered benzoquinone methacrylates

Sterically hindered p- and o-benzoquinone methacrylates, viz., 2,5-di(tert-butyl)-3,6-di-oxocyclohexa-1,4-dienyl methacrylate and 2,5-di(tert-butyl)-3,4-dioxocyclohexa-1,5-dienyl methacrylate, were synthesized by O-acylation of the lithium and tetrabutylammonium salts of 3,6-di(tert-butyl)-2-hydroxy-p-benzoquinone with methacryloyl chloride. The influence of the nature of cation and solvent on regioselectivity of the acylation was studied. The o-benzoquinone derivative obtained can serve as a paramagnetic ligand in metal complexes.     

Reaction of superoxo Co(III) complexes with 2,6-di-t-butyl-p-benzoquinone methides

Superoxo Co(III) complexes derived from Co(Salpr) and [Co(CN)₅]^3? reacted with 2,6-di-$\text{t}$-butyl-$\text{p}$-benzoquinone methides to give 2,6-di-$\text{t}$-butyl-$\text{p}$-benzoquinone and 2,6-di-$\text{t}$-butyl-2,5-cyclohexadienonespirooxiranes as the main products, which are considered to result from nucleophilic attack by the superoxo species on the exo double bond of the quinone methides.     

Spectrophotometric Method for the Determination of Polyphenol Oxidase Activity by Coupling of 4-tert-Butyl-o-Benzoquinone and 4-Amino-N,N-Diethylaniline

ABSTRACT

We describe a spectrophotometric analytical method for the detection of polyphenol oxidase activity in an aqueous solution. The assay is based on the coupling reaction between 4-tert-butyl-o-benzoquinone, generated during the enzyme-catalyzed reaction acting on 4-tert-butylcatechol, and the aromatic amine, 4-amino-N,N-diethylaniline to yield a blue adduct (λ_max 625 nm). This blue adduct exhibited spectral features different from the parent phenol and from the o-quinone. Polyphenol oxidase activities extracted from potatoes, and sunflower seedlings were assayed. The proposed method presents several advantages over the spectrophotometric measurement of 4-tert-butyl-o-benzoquinone. The duration of the linear period was increased, allowing a better determination of its value. The molar extinction coefficient of the blue adduct was higher than that of the 4-tert-butyl-o-benzoquinone; therefore the limitation i8542948 by the comparatively low ? for the 4-tert-butyl-o-benzoquinone is overcome. This is of great importance when considering the inertness of the 4-tert-butyl-o-benzoquinone towards some common coupling agents such as 3-methyl-benzothiazolin-2-one hydrazone.     

Reaction of 3,6-di-tert-butyl-o-benzoquinone with dimedone. Functionalized derivatives of hinderedo-quinones and catechols

The reaction of 3,6-di-tert-butyl-o-benzoquinone with dimedone in the presence of a catalytic amount of Et₃N occurs as repeated 1,4-nucleophilic addition-oxidation and isomerization of a tricyclic quinone into quinomethane. The intermediate products were isolated and characterized. Semiquinone complexes of quinones were studied by ESR in solution. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2206–2209, December, 1997.     

Interaction of 3,5-di-tert-butyl-o-benzoquinone with secondary amines—a pathway to new sterically hindered N,N-disubstituted o-aminophenols

The interaction of 3,5-di-tert-butyl-o-benzoquinone with secondary amines has been studied. The synthetic procedure was developed in order to synthesize a series of new N,N-disubstituted o-aminophenols. The interaction of 3,5-di-tert-butyl-o-benzoquinone with dimethylamine leads to 2-(N,N-dimethylamino)-4,6-di-tert-butyl-phenol, which is oxidized in the reaction medium by the parent 3,5-di-tert-butyl-o-benzoquinone forming spirocompound 4,5′,6,7′-tetra-tert-butyl-3′-methyl-3′H-spiro[1,3-benzodioxol-2,2′-[1,3]benzoxazole].     

Features of photolytic transformation of [4-(2-methyl-5-t-butyl-cyclohexadiene-1,5-dion-3,4-yl)-3-methyl-6-<Emphasis Type="Italic">tert</Emphasis>-butyl-catecholato]triphenylantimony(V)

Photolysis of [4-(2-methyl-5-tert-butyl-cyclohexadiene-1,5-dion-3,4-yl)-3-methyl-6-t-butyl-catecholato] triphenylantimony(V) in toluene by irradiation with the light of wavelength 546 nm leads to excitation of the molecule of parent compound which reacts with a molecule of Ph3SbCatQ affording 4,4′-di-(3-methyl-6-tert-butyl-o-benzoquinone) and 4,4′-di[(3-methyl-6-tert-butyl-catecholato)triphenylantimony(V)]. The formed compounds react with each other returning the system into the initial state. Action of light of wavelength 313 and 405 nm on the initial reaction mixture leads to the formation of carbon monoxide, Ph3SbCatCatSbPh3 and the products of photolytic transformation of 4,4′-di(3-methyl-6-tert-butyl-o-benzoquinone).     

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.     

5-{5-(bicyclo[2.2.1]hept-2-enyl)hydroxymethyl}-3,6-di-<Emphasis Type="Italic">tert</Emphasis>-butyl<Emphasis Type="Italic">o</Emphasis>-benzoquinone and related polymers. Synthesis and some properties

A norbornene-containing ortho-quinone, 5-{5-(bicyclo[2.2.1]hept-2-enyl)hydroxymethyl)-3,6-ditert-butyl-o-benzoquinone, was synthesized by the nucleophilic addition of 5-(hydroxymethyl)bicyclo[2.2.1] hept-2-ene to 3,6-di-tert-butyl-o-benzoquinone. The structure of the compound was established by the X-ray analysis. The monomer obtained undergoes metathesis polymerization in the presence of Grubbs catalyst of the third generation with the formation of polynorbornene containing quinone fragments in the side chains.     

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 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.     

New 1,1-amino hydroperoxides from regioselective oxygenation of 4-(n-arylmethyleneamino)-2,6-di-t-butylphenols.

The oxygenation of 4-(N-arylmethyleneamino)-2,6-di-$\text{t}$-butylphenols with Co(Salpr), a five coordinate Co(II0 Schiff base complex, in CH₂Cl₂ results in the regioselective hydroperoxylation at the imino carbon to give N-(l-aryl-l-hydroperoxymethyl)-3,5-di-$\text{t}$-butyl-$\text{p}$-benzoquinone monoimines, which give exclusively the corresponding amides and 2,6-di-$\text{t}$-butyl-$\text{p}$-benzoquinone in an aerobic solution of KOH in 90% EtOH.     

Reaction of superoxo Co(III) complex with quinones formation of a semiquinone Co(III) complex

The superoxo complex [Co(CN)₅O₂]^3- was found to act as a reducing agent towards quinones. One-electron reduction took place with $\text{o}$-quinones whereas two-electrons reduction with $\text{p}$-quinones. 3,5-Di-$\text{t}$-butyl-$\text{o}$-benzoquinone gave the corresponding semiquinone Co(III) complex quantitatively.     

Synthesis of aromatic polyesters and polyamides by alternating copolymerizations of 1,4-dicarbonyl-1,4-dihydronaphthalene with bezoquinones and benzoquinone diimines

1,4-Dicarbonyl-1,4-dihydronaphthalene ( 1 ) was synthesized by the dehydrochlorination reaction of 1,4-dihydronaphthalene-1,4-dicarbonyl chloride with triethylamine and obtained as its very dilute solution, but it easily polymerized in the concentration as high as 0.1 mol/L to give its polymer. 1 generated in situ by the dehydrochlorination reaction of 1,4-dihydronaphthalene-1,4-dicarbonyl chloride in a deoxygenated toluene polymerized alternatingly with benzoquinones such as 2-dodecylthio-p-benzoquinone, 2,5-di(tert-butyl)-p-benzoquinone, p-benzoquinone, and 2,3-dichloro-5,6-dicyano-p-benzoquinone, and with benzoquinone diimines such as N,N′-diethoxycarbonyl-p-benzoquinone diimine, N,N′-dibenzoyl-p-benzoquinone diimine, and N,N′-diphenyl-p-benzoquinone diimine to give aromatic polyesters and polyamides, respectively. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1929–1936, 1998