Preparation and properties of phosphaethynes bearing bulky aryl groups with electron-donating substituents at the para position

Phosphaethynes bearing a 2,6-di-tert-butyl-4-(dimethylamino)phenyl, 2,6-di-tert-butyl-4-methoxyphenyl, or 2,6-di-tert-butylphenyl group were prepared. A (31)P NMR spectroscopic investigation of the chemical shifts indicated that electron-donating groups at the para position cause shifts to a higher field. Bathochromic shifts caused by the electron-donating groups were apparently observed in UV-vis spectra. The structure of 2-[2,6-di-tert-butyl-4-(dimethylamino)phenyl]-1-phosphaethyne was analyzed by X-ray crystallography.     

Synthesis of 1-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-r-benzimidazoles

Reaction of 2,6-di-tert-butyl-1,4-benzoquinone with o-phenylendiamine gives 2,6-di-tert-butyl-1,4-benzoquinone-4-(N-o-aminophenyl)imine which reacts smoothly with heterocyclic, aromatic and aliphatic aldehydes to form (1-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-substituted benzimidazoles.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 483–485, April, 1990.     

Effects of oxygen in the photolysis of 2,6-di-tert-butyl-1,4-benzoquinonediazide in CCl4

Conclusions The photolysis of 2,6-di-tert-butyl-1,4-benzoquinonediazide in CCl₄, gives 2,6-di-tert-butyl-1,4-benzoquinone in the presence of O₂ in addition to the cage product, 4-chloro-4-trichloromethyl-2,6-di-tert-butylcyclohexadienone. A mechanism has been proposed for the photolysis of the quinonediazide in the presence and absence of oxygen.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2325–2327, October, 1987.     

ESR study of free radicals produced from the reaction of o-substituted phenyl methacrylates with tert-butoxy radical

ESR spectra of radicals produced from the reactions of phenyl methacrylate (PMA) and four o-substituted PMAs, 2,4,6-trimethyl-, 2,6-diisopropyl-, 2,6-di-tert-butyl-, and 2,6-di-tert-butyl-4-methyl-PMAs, with tert-butyoxy radical were measured in 2-methyltetrahydrofuran over the temperature range of ?53 to ?15°C. The coupling constants of the β-methylene protons observed varied with the bulkiness of the o-substituents, whereas the p-substitution did not affect the pattern of the spectra. 2,6-Diisopropyl- and 2,4,6-timethyl-PMAs, which can form homopolymers, gave 5- and 13-line spectra, respectively. For the radicals from 2,6-di-tert-butyl- and 2,6-di-tert-butyl-4-methyl-PMAs, the same 8-line spectrum was observed, indicating that the coupling constant of one of the β-methylene protons was too small to detect. Conformations of the radicals were deduced from the coupling constants of the β-methylene protons. Variation of the ESR spectrum according to the bulkiness of the o-substituent was interpreted as a consequence of steric interactions between the polymer chain bound to the β carbon and the substituents, and the α-methyl group.     

2,6-di-tert-butyl-4-perimidylphenols and their oxidation

1,8-Naphthylenediamine was reacted with 2,6-di-tert-butyl-4-formyl-phenol to produce 2,6-di-tert-butyl-4-(1,3-dihydro-perimidyl) phenol (I). The latter was coverted into 2,6-di-tert-butyl-4-(1H-perimidyl)phenol (II) by oxidizing I with sodium pyrosulfate. When phenol II was oxidized by lead dioxide in toluene and THF, the EPR spectra revealed a 12-component multiplet with perimidyl splitting constants a¹ _N=a³ _N=a_H ^NH=0.2 mT; a_H ^6.7=0.6 mT.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 1, pp. 64–67, January, 1992.     

Novel ferrocene-based inhibitor of proteins glycation

Russian Chemical Bulletin - Antioxidant and antiglycating activities of 2,6-di-tert-butyl-4-[N-(4-pyridyl)iminomethyl]phenol (1), 2,6-di-tert-butyl-4-[N-(3-pyridylmethyl)-iminomethyl]phenol (2) and...     

1-oxo-2,2,6,6-tetramethyl-4-chloropiperidinium perchlorate. A new facile oxidant for phenol coupling

The title compound (1) oxidizes 2,6-di-tert-butylphenol (2), 2,6-di-tert-butyl-4-methylphenol (3), 2,6-di-tert-butyl-4-(dipnenylmethyl)phenol (4), and p-naphthol (5), to quinones in good yield under mild conditions in acetonitrile. For unsubstituted phenols the reaction takes place in two ways, phenol (6) is oxidized to quinhydrone (7), while the oxidation products of the phenols, α-naphthol, catechol and 2,4-dihydroxyl-naphthol were only polymers.     

Use of an automated on-line SPE-HPLC method to monitor caffeine and selected aniline and phenol compounds in aquatic systems of Macedonia-Thrace, Greece

Caffeine and selected aniline and phenol compounds have been monitored in the river, lake, and ground water of Northern Greece (Macedonia-Thrace) from September 1999 to December 2000 by means of a fully automated on-line SPE-HPLC method. Among the target aniline and phenol compounds the most abundant was 2,6-di-tert-butyl-4-methylphenol, which was found to be present in both surface and ground water samples. Caffeine was also very frequently present in river and ground water, although its presence in lake water was rare. Caffeine and 2,6-di-tert-butyl-4-methylphenol were also monitored by off-line SPE of water samples and GC-ion-trap MS analysis of extracts.     

Chemical polarization of nuclei

Conclusions The reaction of 2,6-di-tert-butyl-1,4-benzoquinonediazide with primary aliphatic amines leads to the formation of intermediate unstable triazenes which, in turn, break down through a radical mechanism to form 2,6-di-tert-butylphenol and 2,6-di-tert-butyl-p-benzoquinone, the final reaction products.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 771–775, April, 1977.     

Rigid NON- and NSN-ligand complexes of tetravalent and trivalent uranium: comparison of U-OAr2 and U-SAr2 bonding

A rigid NSN-donor proligand, 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylthioxanthene (H(2)[TXA(2)], 1) was prepared by palladium-catalyzed coupling of 2,6-diisopropylaniline with 4,5-dibromo-2,7-di-tert-butyl-9,9-dimethylthioxanthene. Deprotonation of 1 using (n)BuLi provided Li(2)(DME)(2)[TXA(2)] (2), and subsequent reaction with UCl(4) afforded [Li(DME)(3)][(TXA(2))UCl(3)] (4). The analogous NON-donor ligated complex [(XA(2))UCl(3)K(DME)(3)] [3; XA(2) = 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylxanthene] was prepared by the reaction of K(2)(DME)(x)[XA(2)] with UCl(4). A cyclic voltammogram (CV) of 3 in THF/[NBu(4)][B(C(6)F(5))(4)] at 200 mV s(-1) showed an irreversible reduction to uranium(III) at E(pc) = -2.46 V versus FeCp(2)(0/+1), followed by a product wave at E(1/2) = -1.83 V. Complex 4 also underwent irreversible reduction to uranium(iii) [E(pc) = -2.56 V], resulting in an irreversible product peak at E(pa) = -1.83 V. One-electron reduction of complexes 3 and 4 using K(naphthalenide) under an argon atmosphere in DME yielded 6-coordinate [(XA(2))UCl(DME)] (5) and the thermally unstable 7-coordinate [(TXA(2))U(DME)Cl(2)Li(DME)(2)] (6), respectively. The U-S distances in 4 and 6 are uncommonly short, the C-S-U angles are unusually acute, and the thioxanthene backbone of the TXA(2) ligand is significantly bent. By contrast, the xanthene backbone in XA(2) complexes 3 and 5 is planar. However, κ(3)-coordination and an approximately meridional arrangement of the ancillary ligand donor atoms is maintained in all complexes. DFT and Atoms in Molecules (AIM) calculations were carried out on 3, 4, 5, 6, [(XA(2))UCl(3)](-) (3B), [(TXA(2))UCl(2)(DME)](-) (6B) and [(TXA(2))UCl(DME)] (6C) to probe the extent of covalency in U-SAr(2) bonding relative to U-OAr(2) bonding.     

Cyclohexadienone diazeniumdiolates from nitric oxide addition to phenolates

Sterically hindered phenols react with nitric oxide under basic condititons to give either cyclohexadienone diazeniumdiolates or oximates. Phenols with 2,6-di-tert-butyl and 4-methyl (butylated hydroxy toluene, BHT), 4-ethyl, or 4-methoxy methylene substituents yield the corresponding 2,6-di-tert-butyl-2, 5-cyclohexadienone-4-alkyl-4-diazeniumdiolate salts (4-methyl 1a, 4-ethyl 3a, 4-methoxymethylene 5a). Phenols with 2,6-di-tert-butyl and 4-methylene (2,6-di-tert-butylphenol) substituents yield 4-methoxymethylenediazeniumdiolate (5a) together with 2, 6-di-tert-butyl benzoquinone oximate (6a), while phenols with 2, 6-di-tert-butyl and 4-methylenedimethylamino or hydrogen substituents yield exclusively 2,6-di-tert-butyl benzoquinone oximate (6a). Alkylation of the silver salts of 1a, or treating the O(2)-protonated diazeniumdiolate with diazomethane, both yield mixtures of O(1)- and O(2)-methylated isomers. All the compounds exhibit exothermic thermal decomposition except the quinuclidinium (1e, 3e, 5e) and triethylenediammonium (1f) salts which decompose endothermically. Three of the compounds namely "O(2)-protonated" (Z)-1-[4-(2, 6-di-tert-butyl-4-methyl-cyclohexadienonyl)]diazen-1-ium+ ++-1, 2-diolinic acid (1b), O(2)-methyl (Z)-1-[4-(2, 6-di-tert-butyl-4-methyl-cyclohexadienonyl)]diazen-1-ium+ ++-1,2-diolate (1c), and "O(2)-protonated" (Z)-1-[4-(2, 6-di-tert-butyl-4-methoxymethylenecyclohexadienonyl)]diazen- 1-ium-1, 2-diolinic acid (5b) were characterized by single-crystal X-ray diffraction studies. The diazeniumdiolate framework in all the structures is coplanar with considerable pi-bonding delocalized over the O-N-N-O framework.     

New derivatives of imidazoline 3-oxide and thiazoline with 2,6-dialkylphenol fragments

(2,6-Dialkyl-4-hydroxyphenyl)-2-butanones and aminooxides were used to obtain the corresponding 3-imidazoline 3-oxides. Nitrosylation of 3-imidazoline 3-oxide containing a phenol substituent proceeds either at the imidazoline ring amino group or at the phenol fragment. Intermolecular cyclization of (2,6-di-tert-butyl-4-hydroxyphenyl)-2-butanone with sulfur and ammonia gave a 3-thiazoline as two diastereomers.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 62–67, January, 1986.     

Preparation of nanosilica-immobilized antioxidant and the antioxidation effects in polypropylene

To improve the dispersion of silica in polypropylene（PP） matrix and to avoid physical loss of the antioxidants, nanosilica with dendric polyamidoamines on the surface（SG-PAMAM） was synthesized by using divergent method. Then nanosilica-immobilized antioxidant（SG-PAMAM-AO） was prepared by grafting 2,6-di-tert-butyl-4-aminophenol which was derived from 2,6-di-tert-butyl-4-phenol（AO）. The SG-PAMAM-AO was added into PP by melt mixing to study the aging property. The oxidation induction time of PP/SG-PAMAM-AO and PP/AO compounds was measured. It was found that the antioxidant property of the SG-PAMAM-AO was superior to that of AO. According to the changes of carbonyl absorption before and after photo-thermal aging, the photo-thermal oxidative stability of PP/SG-PAMAM-AO was much higher than that of PP, PP/SG-PAMAM and PP/AO.     

Esr and cidep studies of the photooxidation of phenols in single crystals and in solutions

Photooxidation of single crystals of 2,6-di-tert-butyl-4-methylphenol and 2,6-di-tert-butylphenol, respectively, led to localized pair-wise trapping of triplet phenoxyl radical pairs. Electron ejection is not implicated in the primary photooxidation of phenols in single crystals, but in liquid solutions time-resolved CIDEP observations for the 2,4,6-tritert-butylphenol in hexaftuorobenzene suggest an initial formation of a phenol radical cation from the photoexcited triplet state.     

Complexes of organotin compounds with bis- and trisphosphonate derivatives of 2,6-di-tert-butylphenol having antioxidant activity

Russian Chemical Bulletin - Complexes of organotin compounds R2SnCl2 with bisand trisphosphonate derivatives of 2,6-di-tert-butyl-4-methylphenol (ionol) were synthesized. X-ray diffraction studies...     

Reaction of quinobromide compounds with amines

Conclusions A study was made of the reaction of 4-bromo-4-methyl-2,6-di-tert-butyl-2,5-cyclohexadienone and 4-bromo-2,4,6-tri-tert-butyl-2,5-cyclohexadienone with amines.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2801–2803, December, 1971.     

Reaction of esters of PIII acids with 2,6-di-tert-butyl-4-chloromethylidenecyclohexa-2,5-dienone

Russian Chemical Bulletin - A reaction of PIII acid esters with 2,6-di-tert-butyl-4-chloromethylidenecyclohexa-2,5-dienone leads to the formation of phosphorylated phosphorus ylides,...     

Antioxidants and stabilizers: Part XCV—A co-operative effect between antioxidants N-iso-propyl-N′-phenyl-1,4-phenylene diamine and 2,6-di-tert-butylphenol

In the process of stabilization against the autooxidation of hydrocarbons, the more effective of the two title antioxidants, i.e. N-iso-propyl-N′-phenyl-1,4-phenylenediamine (Ia), is transformed into N-iso-propyl-N′-phenyl-1,4-benzoquinonediimine (IIa). The stability of (IIa) is reduced in an acid medium. In an inert atmosphere and in the presence of weak acids (IIa) reacts quickly with 2,6-di-tert-butylphenol, giving rise to 3,3′,5,5′-tetra-tert-butyl-4,4′-biphenyldiol (VI) and 2,6-di-tert-butyl-4-(4-phenyl-aminophenylamino)-2,5-cyclohexadiene-1-one (Va). In the presence of a relatively low amount of oxygen (Ia), 3,3′,5,5′-tetra-tert-butyldiphenoquinone (IV), (Va) and 2,6-di-tert-butyl-1,4-benzoquinone (VII) are formed. In this way, conditions for co-operative action between the two antioxidants are provided. In the absence of acids the reaction proceeds much more slowly and (Va) is not formed. The mechanism of formation of all the compounds is discussed. There is no pronounced synergism between (Ia) and 2,6-di-tert-butylphenol during the autooxidation of squalene (natural rubber model) in pure oxygen and in a neutral medium. In the presence of 1 vol. % of acetic acid the effectiveness of antioxidant (Ia) is strongly reduced, particularly at elevated concentrations. In a mixture of (Ia) with 2,6-di-tert-butylphenol, a pronounced co-operative effect can be observed.     

Reaction of 4-nitro-2,4,6-tri-tert-butyl-2,5-cyclohexadienone with sterically hindered phenols and diphenylpicrylhydrazine

Conclusions The EPR method was used to study the reaction of 4-nitro-4-methyl-2,6-di-tert-butyl-2,5-cyclohexadienone with some sterically hindered phenols and diphenylpicrylhydrazine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1333–1335, June, 1971.The authors express their gratitude to S. L. Soshk for assistance in the work when taking the oxidation polarograms.     

On the problem of the purity of solvents in HPTLC

Summary The influence of stabilizers (2,6-di-tert-butyl-4-methylphenol and hydroquinone) and impurities in solvents on the reproducibility of the quantitative stability-indicating determination of mebeverine hydrochloride by means of high-performance thin-layer chromatography is reported.