- Selective oxidative para C-C dimerization of 2,6-dimethylphenol
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Mechanistic investigations on the oxidative coupling of 2,6-dimethylphenol have led to the development of a selective and efficient procedure to prepare 3,5,3′,5′-tetramethyl-biphenyl-4,4′-diol, via a C-C coupling, mediated by a hypervalent form of iodine, i.e. (diacetoxyiodo)benzene and for which a mechanism is proposed. The Royal Society of Chemistry 2005.
- Boldron, Christophe,Aromi, Guillem,Challa, Ger,Gamez, Patrick,Reedijk, Jan
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Read Online
- Regioselective oxidative coupling of 2,6-dimethylphenol to tetramethyldiphenoquinone using polyamine dendrimer-encapsulated Cu catalysts
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The polyamine dendrimer-encapsulated Cu complexes are capable of regioselectively catalyzing the oxidative coupling reaction of 2,6-dimethylphenol to tetramethyldiphenoquinone in high yield. The polyamine dendrimer nanovoids encapsulate Cu ions in such a manner that adjacent Cu centers are able to serve as active species for the reaction.
- Maeno, Zen,Okao, Motohiro,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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Read Online
- A dual-functional heterogeneous ruthenium catalyst for the green one-pot synthesis of biphenols
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A green one-pot synthesis of biphenols using O2 and H2 was achieved using a magadiite-supported Ru nanoparticle catalyst. This catalyst selectively promoted the oxidative coupling of phenols to diphenoquinones with O2, followed by the successive reduction of these diphenoquinones to biphenols using H2 in a single reactor.
- Maeno, Zen,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro
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p. 3205 - 3209
(2017/08/16)
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- Solvent-Dependent Facile Synthesis of Diaryl Selenides and Biphenols Employing Selenium Dioxide
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Biphenols are important structure motifs for ligand systems in organic catalysis and are therefore included in the category of so-called "privileged ligands". We have developed a new synthetic pathway to construct these structures by the use of selenium dioxide, a stable, powerful, and commercially available oxidizer. Our new, and easy to perform protocol gives rise to biphenols and diaryl selenides depending on the solvent employed. Oxidative treatment of phenols in acetic acid yields the corresponding biphenols, whereas conversion in pyridine results in the preferred formation of diaryl selenides. As a consequence, we were able to isolate a broad scope of novel diaryl selenides, which could act as pincer-like ligands with further applications in organic synthesis or as ligands in transition metal catalysis.
- Quell, Thomas,Mirion, Michael,Schollmeyer, Dieter,Dyballa, Katrin M.,Franke, Robert,Waldvogel, Siegfried R.
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p. 115 - 119
(2016/05/02)
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- Industrialized synthesis method of high-purity biphenyl diphenol compound
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The invention discloses an industrialized synthesis method of a high-purity biphenyl diphenol compound. The synthesis method comprises the steps that a phenolic compound A of which the ortho-position or para-position is a hydrogen atom serves as the raw material, alkali metal hydroxide or alkaline earth metal hydroxide or weak-acid alkali metal salt serves as a catalyst, different phenolic compounds are added to serve as oxidation regulators, all the substances are mixed and heated to 65 DEG C-185 DEG C, and meanwhile oxygen or air is blown into the mixture for an oxidation coupling reaction; after the PH value of the reaction system is adjusted through an acidic substance, a disproportionated reaction is conducted in an inert gas environment at the temperature ranging from 65 DEG C to 245 DEG C, and the high-purity biphenyl diphenol compound B or C is obtained. According to the preparation method of the high-purity biphenyl diphenol compound, the steps are simple, the reaction conditions are mild, the cost is low, the reaction materials can be recycled, the product is good in color, the product purity reaches up to 99.9 percent, and the preparation method is very suitable for industrialized production.
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Paragraph 0023; 0024
(2016/11/14)
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- Selective c-c coupling reaction of dimethylphenol to tetramethyldiphenoquinone using molecular oxygen catalyzed by cu complexes immobilized in nanospaces of structurally-ordered materials
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Two high-performance Cu catalysts were successfully developed by immobilization of Cu ions in the nanospaces of poly(propylene imine) (PPI) dendrimer and magadiite for the selective C-C coupling of 2,6-dimethylphenol (DMP) to 3,3′,5,5′-tetramethyldiphenoquinone (DPQ) with O2 as a green oxidant. The PPI dendrimer encapsulated Cu ions in the internal nanovoids to form adjacent Cu species, which exhibited significantly high catalytic activity for the regioselective coupling reaction of DMP compared to previously reported enzyme and metal complex catalysts. The magadiite-immobilized Cu complex acted as a selective heterogeneous catalyst for the oxidative C-C coupling of DMP to DPQ. This heterogeneous catalyst was recoverable from the reaction mixture by simple filtration, reusable without loss of efficiency, and applicable to a continuous flow reactor system. Detailed characterization using ultraviolet-visible (UV-vis), Fourier transform infrared (FTIR), electronic spin resonance (ESR), and X-ray absorption fine structure (XAFS) spectroscopies and the reaction mechanism investigation revealed that the high catalytic performances of these Cu catalysts were ascribed to the adjacent Cu species generated within the nanospaces of the PPI dendrimer and magadiite.
- Maeno, Zen,Mitsudome, Takato,Mizugaki, Tomoo,Jitsukawa, Koichiro,Kaneda, Kiyotomi
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p. 3089 - 3106
(2015/09/02)
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- {Cu2+-Co3+-Cu2+} and {Cu 2+-Fe3+-Cu2+} heterobimetallic complexes and their catalytic properties
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We report on the heterobimetallic complexes {Cu+-Co 3+-Cu+} (3), {Cu+-Fe3+-Cu +} (4), {Cu2+-Co3+-Cu2+} (5), and {Cu2+-Fe3+-Cu2+} (6) and show their catalytic applications in the oxidation of hindered phenols and the oxidative coupling of terminal alkynes. The former reaction produces C-C-coupled and dealkylated products, whereas the latter leads to the homo- and heterocoupling of terminal alkynes. The facile redox interconversion between Cu+ and Cu 2+ for the secondary metal ions in these heterobimetallic complexes appears to be essential for the observed catalysis, and an important design aspect is better substrate accessibility and the use of molecular oxygen as the sole oxidant. Heterobimetallic complexes {Cu+-Co3+-Cu +} (3), {Cu+-Fe3+-Cu+} (4), {Cu 2+-Co3+-Cu2+} (5), and {Cu2+-Fe 3+-Cu2+} (6) have been used as catalysts for the oxidation of substituted phenols and the oxidative homo- and heterocoupling of terminal alkynes. Copyright
- Srivastava, Sumit,Ali, Afsar,Tyagi, Adish,Gupta, Rajeev
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p. 2113 - 2123
(2014/05/06)
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- Selective oxidative homo-and cross-coupling of phenols with aerobic catalysts
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Simple catalysts that use atom-economical oxygen as the terminal oxidant to accomplish selective ortho-ortho, ortho-para, or para-para homo-couplings of phenols are described. In addition, chromium salen catalysts have been discovered as uniquely effective in the cross-coupling of different phenols with high chemo-and regioselectivity.
- Lee, Young Eun,Cao, Trung,Torruellas, Carilyn,Kozlowski, Marisa C.
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supporting information
p. 6782 - 6785
(2014/06/09)
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- {Cu2+-Co3+-Cu2+} and {Cu2+-Fe3+-Cu2+} heterobimetallic complexes and their catalytic properties
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We report on the heterobimetallic complexes {Cu+-Co3+-Cu+} (3), {Cu+-Fe3+-Cu+} (4), {Cu2+-Co3+-Cu2+} (5), and {Cu2+-Fe3+-Cu2+} (6) and show their catalytic applications in the oxidation of hindered phenols and the oxidative coupling of terminal alkynes. The former reaction produces C-C-coupled and dealkylated products, whereas the latter leads to the homo- and heterocoupling of terminal alkynes. The facile redox interconversion between Cu+ and Cu2+ for the secondary metal ions in these heterobimetallic complexes appears to be essential for the observed catalysis, and an important design aspect is better substrate accessibility and the use of molecular oxygen as the sole oxidant. Heterobimetallic complexes {Cu+-Co3+-Cu+} (3), {Cu+-Fe3+-Cu+} (4), {Cu2+-Co3+-Cu2+} (5), and {Cu2+-Fe3+-Cu2+} (6) have been used as catalysts for the oxidation of substituted phenols and the oxidative homo- and heterocoupling of terminal alkynes.
- Srivastava, Sumit,Ali, Afsar,Tyagi, Adish,Gupta, Rajeev
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p. 2113 - 2123
(2015/04/27)
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- Efficient oxidative coupling of 2,6-disubstituted phenol catalyzed by a dicopper(II) complex
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Complexation of a rigid multi-pyridine ligand bis(2-pyridyl)-1,8- naphthyridine (bpnp) with [Cu2(TFA)4] (TFA = trifluoroacetate) resulted in the formation of a dinuclear copper(ii) complex, namely [Cu2(bpnp)(μ-OH)(TFA)3] (1). This complex has been characterized by X-ray crystallographic, spectroscopic and elemental analyses. Complex 1 is an efficient catalyst for the oxidative coupling of various 2,6-disubstituted phenols with molecular oxygen. Yields and selectivity depend on the reaction conditions employed, the best results being obtained in isopropanol or dioxane at 90 °C with yields of >99%. Mechanistic pathway of the catalysis is discussed.
- Liao, Bei-Sih,Liu, Yi-Hung,Peng, Shei-Ming,Liu, Shiuh-Tzung
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scheme or table
p. 1158 - 1164
(2012/03/07)
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- Efficient generation of ortho -quinone methide: Application to the biomimetic syntheses of (±)-schefflone and tocopherol trimers
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An efficient method using silver oxide-mediated oxidation for the synthesis of ortho-quinone methides has been developed and applied to the biomimetic syntheses of novel trimeric natural products, (±)-schefflone and tocopherol trimers. Further studies of the critical trimerization as well as substrate scope and limitations are also reported.
- Liao, Daohong,Li, Houhua,Lei, Xiaoguang
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supporting information; experimental part
p. 18 - 21
(2012/02/04)
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- Carbonic anhydrase inhibitors. Inhibition of human erythrocyte isozymes I and II with a series of antioxidant phenols
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The inhibition of two human cytosolic carbonic anhydrase (hCA, EC 4.2.1.1) isozymes I and II, with a series of phenol derivatives was investigated by using the esterase assay, with 4-nitrophenyl acetate as substrate. 2,6-Dimethylphenol, 2,6-diisopropylphenol (propofol), 2,6-di-t-butylphenol, butylated hydroxytoluene, butylated hydroxyanisole, vanillin, guaiacol, di(2,6-dimethylphenol), di(2,6-diisopropylphenol), di(2,6-di-t-butylphenol), and acetazolamide showed KI values in the range of 37.5-274.5 μM for hCA I and of 0.29-113.5 μM against hCA II, respectively. All these phenols were non-competitive inhibitors with 4-nitrophenylacetate as substrate. Some antioxidant phenol derivatives investigated here showed effective hCA II inhibitory effects, in the same range as the clinically used sulfonamide acetazolamide, and might be used as leads for generating enzyme inhibitors possibly targeting other CA isoforms which have not been yet assayed for their interactions with such agents.
- Sentuerk, Murat,Guelcin, Ilhami,Dastan, Arif,Irfan Kuefrevioglu, Oe.,Supuran, Claudiu T.
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experimental part
p. 3207 - 3211
(2009/09/08)
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- Enantioselective synthesis of bicyclo[2.2.2]octenones using a copper-mediated oxidative dearomatization/[4 + 2] dimerization cascade
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An enantioselective approach to bicyclo[2.2.2]octenone structures utilizing a copper-mediated asymmetric oxidative dearomatization/[4 + 2] dimerization cascade is described. The total synthesis and absolute stereochemistry reassignment of (+)-aquaticol has been achieved using the methodology. Copyright
- Dong, Suwei,Zhu, Jianglong,Porco Jr., John A.
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p. 2738 - 2739
(2008/09/19)
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- Antioxidant activity of propofol and related monomeric and dimeric compounds
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This study was carried out to investigate the antioxidant activity of propofol (2,6-diisopropylphenol) and its related compounds, butylated hydroxyanisole (BHA), 2,6-dimethylphenol, 2,6-di-t-butylphenol, and their dimeric compounds. The degree of antioxidant activity was evaluated based on the degree of peroxidation induced with Fe-ascorbic acid in egg phosphatidylcholine through the determination of thiobarbituric acid-reactive substances (TBARS) formed during peroxidation. Their antioxidant activities were in the order of dipropofol>di(2,6-di-t-butylphenol)>diBHA>di(2,6-dimethylphenol). Dipropofol, a dimeric compound of propofol, showed the highest antioxidant activities. Dimeric compounds had higher activities than monomeric compounds, and the 1,1-diphenyl-p-picryhydrazyl-trapping ability of dimeric compounds was also greater than those of monomeric compounds (4-10-fold). These results suggest that dimeric phenols may increase their antioxidant activities along with increments in the conjugation system and play a inhibitory role in the propagation of free radical chain reactions.
- Ogata, Masahiro,Shin-Ya, Kazuo,Urano, Shiro,Endo, Toyoshige
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p. 344 - 346
(2007/10/03)
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- Antibacterial activity of dipropofol and related compounds
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Phenolic compounds, in general, exhibit antioxidant and antibacterial activities. We studied antimicrobial activity of the phenolic antioxidants, propofol (2,6-diisopropylphenol), tocopherol, eugenol, butylated hydroxyanisole (BHA), and several of their dimer compounds. Dipropofol (dimer of 2,6-diisopropylphenol) showed strong antibacterial activity against gram-positive strains including methicillin resistant Staphylococcus aureus (MRSA) and vancomycin resistant Enterococci (VRE), while propofol and other monomeric and dimeric phenols having methyl or tert-butyl groups showed no remarkable activity. The results indicated that the dimeric structure of 2,6-diisopropylphenol moiety may play an important role in the antibacterial activity.
- Ogata, Masahiro,Sato, Kanae Tutumimoto,Kunikane, Takao,Oka, Kentaro,Seki, Masako,Urano, Shiro,Hiramatsu, Keiichi,Endo, Toyoshige
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p. 1120 - 1122
(2007/10/03)
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- BIFUNCTIONAL BIPHENYL AND PROCESS FOR PRODUCING BIFUNCTIONAL PHENYLENE ETHER OLIGOMER COMPOUND USING THE SAME
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A process for producing 2,2′,3,3′,5,5′-hexamethyl-[1,1′-biphenyl]-4,4′-diol, which process comprises, while setting a pH of a reaction liquid containing an alkaline aqueous solution, a surfactant, a copper catalyst and 2,3,6-trimethylphenol during a reaction in the range of from 8 to 14 and controlling the variation range of the pH of the reaction liquid within ±1, oxidatively coupling the 2,3,6-trimethylphenol with an oxygen-containing gas, and a process for producing a bifunctional phenylene ether oligomer compound having a controlled average molecular weight, comprising carrying out oxidation polymerization under a proper oxygen concentration.
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- Selective oxidation of phenols to hydroxybenzaldehydes and benzoquinones with dioxygen catalyzed by polymer-supported copper
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Oxidation of 2,6-disubstituted 4-methylphenols with dioxygen by using a CuCl2-poly(4-methyl-4′-vinyl-2,2′-bipyridine) catalyst gave the corresponding 4-hydroxybenzaldehydes in high yields. The activity of the catalyst and the selectivity of the products significantly depended on the reaction conditions and the composition of the catalyst. When the molar ratio of the bipyridine unit of the polymer ligand to Cu was unity, i.e., N/Cu = 2, the best results were obtained. Moreover, the reaction is likely to be promoted by coordination of the products to the catalyst. Similarly, 2,3,6-trimethylphenol and related compounds were converted to p-benzoquinones selectively with a CuCl2-poly(4-vinylpyridine) catalyst. These polymer-supported catalysts were readily recovered and are reusable without noticeable decrease of their activity.
- Takaki, Ken,Shimasaki, Yohei,Shishido, Tetsuya,Takehira, Katsuomi
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p. 311 - 317
(2007/10/03)
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- Catalytic oxidation of hindered phenols by a copper(I) complex and dioxygen
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The dioxygen reaction product of a binuclear copper(I) complex of a new m-xylyl-based ligand has proven to be a catalyst in the promotion of oxidative carbon-carbon coupling of hindered phenols, which leads to bisphenol and diphenoquinones. (C) 2000 Elsevier Science Ltd.
- Gupta,Mukherjee
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p. 7763 - 7767
(2007/10/03)
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- (Nitrosonaphtholato)metal complex-catalyzed oxidation of phenols and alkenes
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Bis(1-nitroso-2-naphtholato)manganese(II), tris(1-nitroso-2-naphtholato)manganese(III), tris(2-nitroso-1-naphtholato)manganese(III), bis(1-nitroso-2-naphtholato)cobalt(II), bis(1-nitroso-2-naphtholato)nickel(II), bis(1-nitroso-2-naphtholato)copper(II) and bis(1-nitroso-2-naphtholato)zinc(II) were prepared and their catalytic abilities in the oxidation of phenols were examined. The best yields of diphenoquinones were obtained when the catalytic oxidation using bis(1-nitroso-2-naphtholato)manganese(II) was carried out at 23°C under an oxygen atmosphere (1 atm) in the presence of a phosphine ligand. Likewise, phenols were completely converted to the corresponding diphenoquinones together with small amounts of benzoquinones under an oxygen pressure (20 atm) at 50°C in a short period of time. It was proven that the manganese(II) catalyst, molecular oxygen, and phosphine ligand were essential for the catalytic phenol oxidation. On the other hand. bis(1-nitroso-2-naphtholato)manganese(II)-catalyzed epoxidation of alkenes was only effective when iodosylbenzene was used. The catalytic oxidation mechanism was discussed on the basis of the measurement of cyclic voltammograms of the (nitrosonaphtholato)metal complexes, isolated intermediates, and effect of additives.
- Nishino, Hiroshi,Satoh, Hideaki,Yamashita, Mayumi,Kurosawa, Kazu
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p. 1919 - 1924
(2007/10/03)
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- Method using aromatic oxidizing agents
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A method for oxidizing certain aromatic compounds such as biphenols using an oxidizing agent such as peroxide in a solvent such as a concentrated alkanoic acid or and alkane diol.
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- Novel photochemical coupling of hindered phenols in the presence of acridine mechanistically probed by CIDEP
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Irradiation of hindered phenols in the presence of acridine as a light absorber gives bisphenols and biacridane.CIDEP study establishes the path of hydrogen abstraction by the triplet acridine.The overall mechanism is proposed by the product analysis and the CIDEP studies.
- Okada, Keiji,Okubo, Katsura,Oda, Masaji,Murai, Hisano
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p. 845 - 846
(2007/10/03)
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- Choice of Manganese(III) Complexes for the Synthesis of 4,4'-Biphenyldiols and 4,4'-Diphenoquinones
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2,6-Disubstituted phenols are oxidized with tris(2,4-pentanedionato)manganese(III), , in glacial acetic acid to give the corresponding 4,4'-biphenyldiols in high yields, whereas similar reactions using manganase(III) acetate, , instead of quantitatively yield the corresponding 4,4'-diphenoquinones.Cross-coupling reactions of 2,6-di-t-butylphenol and other substituted phenols afford the corresponding cross-coupled 4,4'-biphenyldiols and 4,4'-diphenoquinones together with oxidation products derived from them starting phenols themselves.The advantageous use of and Mn(OAc)3> in the ubiqitous phenol coupling reaction is discussed.
- Nishino, Hiroshi,Nobuyuki, Itoh,Nagashima, Makiko,Kurosawa, Kazu
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p. 620 - 622
(2007/10/02)
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- Mushroom tyrosinase catalysed coupling of hindered phenols: A novel approach for the synthesis of diphenoquinones and bisphenols
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An efficient oxidative carbon-carbon coupling of hindered phenols leading to diphenoquinones and bisphenols by mushroom tyrosinase is reported.
- Pandey,Muralikrishna,Bhalerao
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p. 3771 - 3774
(2007/10/02)
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