- Synthesis of phenyl-substituted conduritol B and its mechanism of formation
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The phenyl-substituted conduritol B 8 was prepared in racemic form in a five-step sequence starting from 2-phenyl-1,4-benzoquinone (10) (Scheme 1). The reaction mechanism of the key step 12b → 13 is discussed (Scheme 2).
- Cantekin, Seda,Caliskan, Rasit,Sahin, Ertan,Balci, Metin
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- Oxidative Dearomatization of Phenols and Polycyclic Aromatics with Hydrogen Peroxide Triggered by Heterogeneous Sulfonic Acids
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We report herein a method for the oxidative dearomatization of phenols and bare polycyclic arenes into the corresponding quinoid derivatives using hydrogen peroxide. The reaction is catalyzed by sulfonic acids and best results were achieved using heterogenized species. The best results using phenols were achieved using a hybrid material, namely a perfluorinated polymer functionalized with sulfonic acid groups supported on silica. The dearomatization of polycyclic aromatic hydrocarbons performed better using the polymeric acid catalyst. These methods operate under mild conditions, using mild and benign oxidants and thus minimizing the formation of waste.
- Pancrazzi, Francesco,Maestri, Giovanni,Maggi, Raimondo,Viscardi, Rosanna
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supporting information
p. 5407 - 5414
(2021/10/25)
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- Selective Palladium-Catalyzed α,β-Homodiarylation of Vinyl Esters in Aqueous Medium
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A palladium-catalyzed 1,2-diarylation of vinyl esters with arylboronic acids in water has been developed. This newly elaborated protocol features a good functional group tolerance and provides one-step access to 1,2-diarylethanol derivatives under mild reaction conditions. The presented reaction can be carried out in the water at ambient temperature without the addition of any ligands, what makes this procedure environmentally benign. The transformation occurs within a single catalytic cycle and is feasible due to the modification of transition metal catalytic activity through the influence of π-acceptor olefin (benzoquinone) as well as water as a medium. Moreover, this protocol allows to generate entire compound libraries (highly profitable in medicinal chemistry) and utilizes sustainable arylboronic acids as coupling partners under mild conditions. It is also noted that the structure of boron moiety has a great impact on the reaction selectivity, the usage of sterically hindered esters of arylboronic acids influence the reaction course towards stilbenes.
- Brodzka, Anna,Koszelewski, Dominik,Ostaszewski, Ryszard,Trzepizur, Damian,Wilk, Monika
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supporting information
p. 6028 - 6036
(2021/12/10)
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- Zwitterion-induced organic-metal hybrid catalysis in aerobic oxidation
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In many metal catalyses, the traditional strategy of removing chloride ions is to add silver salts via anion exchange to obtain highly active catalysts. Herein, we reported an alternative strategy of removing chloride anions from ruthenium trichloride using an organic [P+-N-] zwitterionic compound via multiple hydrogen bond interactions. The resultant organic-metal hybrid catalytic system has successfully been applied to the aerobic oxidation of alcohols, tetrahydroquinolines, and indolines under mild conditions. The performance of zwitterion is far superior to that of many other common Lewis bases or Br?nsted bases. Mechanistic studies revealed that the zwitterion triggers the dissociation of chloride from ruthenium trichloride via nonclassical hydrogen bond interaction. Preliminary studies show that the zwitterion is applicable to catalytic transfer semi-hydrogenation.
- Hu, Rong-Bin,Lam, Ying-Pong,Ng, Wing-Hin,Wong, Chun-Yuen,Yeung, Ying-Yeung
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p. 3498 - 3506
(2021/04/07)
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- Strategies towards potent trypanocidal drugs: Application of Rh-catalyzed [2?+?2?+?2] cycloadditions, sulfonyl phthalide annulation and nitroalkene reactions for the synthesis of substituted quinones and their evaluation against Trypanosoma cruzi
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Rhodium-catalyzed [2 + 2 + 2] cycloadditions, sulfonyl phthalide annulations and nitroalkene reactions have been employed for the synthesis of 56 quinone-based compounds. These were evaluated against Trypanosoma cruzi, the parasite that causes Chagas disease. The reactions described here are part of a program that aims to utilize modern, versatile and efficient synthetic methods for the one or two step preparation of trypanocidal compounds. We have identified 9 compounds with potent activity against the parasite; 3 of these were 30-fold more potent than benznidazole (Bz), a drug used for the treatment of Chagas disease. This article provides a comprehensive outline of reactions involving over 120 compounds aimed at the discovery of new quinone-based frameworks with activity against T. cruzi.
- Wood, James M.,Satam, Nishikant S.,Almeida, Renata G.,Cristani, Vinicius S.,de Lima, Dênis P.,Dantas-Pereira, Luiza,Salom?o, Kelly,Menna-Barreto, Rubem F.S.,Namboothiri, Irishi N.N.,Bower, John F.,da Silva Júnior, Eufranio N.
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- Chemoproteomics of an indole-based quinone epoxide identifies druggable vulnerabilities in vancomycin-resistant staphylococcus aureus
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The alarming global rise in fatalities from multidrug-resistant Staphylococcus aureus (S. aureus) infections has underscored a need to develop new therapies to address this epidemic. Chemoproteomics is valuable in identifying targets for new drugs in different human diseases including bacterial infections. Targeting functional cysteines is particularly attractive, as they serve critical catalytic functions that enable bacterial survival. Here, we report an indole-based quinone epoxide scaffold with a unique boat-like conformation that allows steric control in modulating thiol reactivity. We extensively characterize a lead compound (4a), which potently inhibits clinically derived vancomycin-resistant S. aureus. Leveraging diverse chemoproteomic platforms, we identify and biochemically validate important transcriptional factors as potent targets of 4a. Interestingly, each identified transcriptional factor has a conserved catalytic cysteine residue that confers antibiotic tolerance to these bacteria. Thus, the chemical tools and biological targets that we describe here prospect new therapeutic paradigms in combatting S. aureus infections.
- Kulkarni, Amogh,Soni, Isha,Kelkar, Dhanashree S.,Dharmaraja, Allimuthu T.,Sankar, Rathinam K.,Beniwal, Gaurav,Rajendran, Abinaya,Tamhankar, Sharvari,Chopra, Sidharth,Kamat, Siddhesh S.,Chakrapani, Harinath
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supporting information
p. 6785 - 6795
(2019/08/20)
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- Activated Carbon-Promoted Dehydrogenation of Hydroquinones to Benzoquinones, Naphthoquinones, and Anthraquinones under Molecular Oxygen Atmosphere
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We found that the activated carbon-molecular oxygen system promotes the conversion of hydroquinones to benzoquinones, naphthoquinones, and anthraquinones, which are often found in natural products and pharmaceuticals. In particular, the one-pot synthesis of naphthoquinones and anthraquinones involving a Diels-Alder reaction is a useful protocol for this purpose.
- Kim, Sanghun,Matsubara, Ryosuke,Hayashi, Masahiko
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p. 2997 - 3003
(2019/03/08)
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- Mn-Catalyzed 1,6-conjugate addition/aromatization of: Para -quinone methides
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A series of ferrocenyl triazole ligands have been synthesized and characterized, which proved to be effective for the Mn-catalyzed 1,6-conjugate addition/aromatization of para-quinone methides with good to high yields under mild conditions. This protocol provided an efficient and practical route to the synthetically interesting functionalized quinones, methines and their analogues.
- Yang, Bobin,Yao, Wei,Xia, Xiao-Feng,Wang, Dawei
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supporting information
p. 4547 - 4557
(2018/06/29)
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- Metal-free, air-promoted, radical-mediated arylation of benzoquinone with phenylhydrazines
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An efficient, economic, and air-promoted metal-free method for direct arylation of benzoquinone with phenylhydrazines was developed. This approach leads to the formation of corresponding [1,1′-biphenyl]-2,5-dione derivatives as biological and pharmaceutic
- Sayahi, Mohammad Hosein,Ansari, Samira,Saghanezhad, Seyyed Jafar,Mahdavi, Mohammad
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supporting information
p. 703 - 706
(2018/09/27)
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- Silver-Catalyzed Minisci Reactions Using Selectfluor as a Mild Oxidant
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A new method for silver-catalyzed Minisci reactions using Selectfluor as a mild oxidant is reported. Heteroarenes and quinones both participate in radical C-H alkylation and arylation from a variety of carboxylic and boronic acid radical precursors. Several oxidatively sensitive and highly reactive radical species are successful, providing structures that are challenging to access by other means.
- Galloway, Jordan D.,Mai, Duy N.,Baxter, Ryan D.
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supporting information
p. 5772 - 5775
(2017/11/10)
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- Catalytic asymmetric [2+2] cycloaddition between quinones and fulvenes and a subsequent stereoselective isomerization to 2,3-dihydrobenzofurans
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The catalytic enantioselective [2+2] cycloaddition between quinones and fulvenes was achieved, for the first time, by the use of a chiral copper(ii) complex catalyst. The transformation afforded a series of enantiomerically enriched [6,4,5]-tricyclic cyclobutane derivatives in good yields with excellent regio- and stereoselectivities. Furthermore, the [2+2] adducts could be easily converted into formal [3+2] adducts efficiently and stereoselectively.
- Zheng, Haifeng,Xu, Chaoran,Wang, Yan,Kang, Tengfei,Liu, Xiaohua,Lin, Lili,Feng, Xiaoming
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supporting information
p. 6585 - 6588
(2017/07/10)
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- Hydroquinone-Based Biarylic Polyphenols as Redox Organocatalysts for Dioxygen Reduction: Dramatic Effect of Orcinol Substituent on the Catalytic Activity
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A series of 18 new biaryls has been synthesized and investigated with regard to their organocatalytic efficiency. They consist of a hydroquinone core linked to a phenol or a resorcinol moiety. It is shown that the resorcinol moiety substituted on its meta position has a strong impact on the catalytic activities of these compounds towards the reduction of dioxygen by diethylhydroxylamine (DEHA) in aqueous medium. While the derivative consisting of the two cores spaced by three methylene units is completely inactive, substitution on the hydroquinone part leads to tremendously active catalysts, especially the biaryl consisting of methoxyhydroquinone-orcinol. Two mechanisms are proposed to explain the dramatic efficiency of the novel hydroquinone-based biarylic polyphenols for the catalytic reduction of dioxygen, both considering the influence of the orcinol moiety on the semiquinone anion intermediate. As a first hypothesis, this substituent could promote its direct reduction by DEHA to regenerate the hydroquinone, which will react again to regenerate the semiquinone. On the other hand, an intramolecular hydrogen bond could enhance the reactivity of the semiquinone anion toward dioxygen by an addition–elimination mechanism. In this case, the elimination would provide the corresponding quinone but, since the reduction of the quinones by DEHA is much slower than the observed kinetics, a reduction by DEHA prior to the elimination has to be considered to generate the semiquinone anion instead of the quinone. (Figure presented.).
- Lebeuf, Rapha?l,Nardello-Rataj, Véronique,Aubry, Jean-Marie
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supporting information
p. 268 - 278
(2017/02/05)
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- Rh-Catalyzed Reactions of 1,4-Benzoquinones with Electrophiles: C-H Iodination, Bromination, and Phenylselenation
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Under Rh-catalyzed conditions, typically electrophilic 1,4-benzoquinones exhibit nucleophilic reactivity, such that exposure to appropriate electrophiles generates products of C-H iodination, bromination, and phenylselenation. This provides a mild and general method for direct halofunctionalization, and the first method that can achieve direct C-H phenylselenation of this compound class. The scope and limitations of the new protocols are outlined, and representative derivatizations are highlighted.
- Jardim, Guilherme A. M.,Bower, John F.,Da Silva Júnior, Eufranio N.
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p. 4454 - 4457
(2016/09/28)
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- Ir-catalyzed arylation, alkylation of quinones with boronic acids through C-C coupling
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Ir-catalyzed arylation, alkylation of quinones with boronic acids was developed under room temperature. Both aryl and alkyl boronic acids are suitable for this transformation. This expands the application scope of the iridium catalyst. This is also an excellent proof that iridium catalysts can be used in the C-C coupling of quinones and naphthoquinones with alkyl boronic acids.
- Wang, Dawei,Ge, Bingyang,Ju, Anqi,Zhou, Yucheng,Xu, Chongying,Ding, Yuqiang
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supporting information
p. 30 - 33
(2015/01/30)
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- Synthesis of aryl- and alkylquinones through rhodium-catalyzed C-C coupling under mild conditions
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A direct arylation, alkylation of quinones with aryl and alkyl boronic acids through rhodium-catalyzed C-C coupling has been developed under mild conditions. [CpRhCl2]2 was shown to be the most effective catalyst for the transformation. More importantly, good to excellent yields were obtained under room temperature and base-free conditions. This reaction provides a practical, efficient method for the synthesis of aryl- and alkylquinones.
- Wang, Dawei,Ge, Bingyang,Du, Liyong,Miao, Hongyan,Ding, Yuqiang
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supporting information
p. 2895 - 2898
(2015/02/02)
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- Substituent effects on reactive oxygen species (ROS) generation by hydroquinones
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In order to understand the structural aspects of stabilization of hydroquinones and their ability to generate reactive oxygen species (ROS), we designed and synthesized a series of 6-aryl-2,3-dihydro-1,4-benzoquinones. These compounds equilibrate with the corresponding 6-aryl-1,4-dihydroxybenzenes in an organic medium; a linear free energy relationship analysis gave ρ = +2.37, suggesting that this equilibrium was sensitive to electronic effects. The propensity of the compound to enolize appears to determine ROS-generating capability, thus offering scope for tunable ROS generation.
- Dharmaraja, Allimuthu T.,Jain, Charu,Chakrapani, Harinath
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supporting information
p. 9413 - 9417
(2014/12/12)
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- Synthesis of aryl substituted quinones as β-secretase inhibitors: Ligand-free direct arylation of quinones with aryl halides
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The simple ligand-free direct arylation of quinones with aryl halides applying Pd(OAc)2as a catalyst in accordance with Heck reaction was studied. This reaction provided a simple and efficient synthetic approach to efficient inhibitors of β-secretase aryl-substituted quinones.
- Wang, Dawei,Ge, Bingyang,Yang, Shuyan,Miao, Hongyan,Ding, Yuqiang
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p. 1615 - 1621
(2015/02/19)
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- Versatile palladium-catalyzed C-H olefination of (hetero)arenes at room temperature
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The room-temperature oxidative C-H/C-H cross-couplings between (hetero)arenes and alkenes, coumarins or quinones have been reported by using a highly electrophilic palladium species [Pd(TFA)2], generated in situ from Pd(OAc)2and TFA, as the catalyst and cheap (NH4)2S2O8as the oxidant under air.
- She, Zhijie,Shi, Yang,Huang, Yumin,Cheng, Yangyang,Song, Feijie,You, Jingsong
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supporting information
p. 13914 - 13916
(2015/01/09)
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- Transition metal-free direct C-H functionalization of quinones and naphthoquinones with diaryliodonium salts: Synthesis of aryl naphthoquinones as β-secretase inhibitors
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A novel ligand-free, transition metal-free direct C.H functionalization of quinones with diaryliodonium salts has been developed for the first time. The transformation was promoted only through the use of a base and gave aryl quinone derivatives in moderate to good yields. This methodology provided an effective and easy way to synthesize β-secretase inhibitors. The radical trapping experiments showed that this progress was the radical mechanism.
- Wang, Dawei,Ge, Bingyang,Li, Liang,Shan, Jie,Ding, Yuqiang
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p. 8607 - 8613
(2015/01/08)
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- Generation of arylated quinones by iron-catalyzed oxidative arylation of phenols: Formal synthesis of phellodonin, sarcodonin ε, leucomelone and betulinan A
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Biologically and pharmaceutically relevant arylated quinones (Quin-Ar) have been synthesized via direct C-H arylation of a variety of phenols using arylboronic acids. An inexpensive, environmentally friendly iron catalyst, ferric sulphate, Fe2(SO4)3, was employed in this operationally simple and efficient method.
- Deb, Arghya,Agasti, Soumitra,Saboo, Tapish,Maiti, Debabrata
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supporting information
p. 705 - 710
(2014/04/03)
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- Iron-catalyzed direct C-H arylation of heterocycles and quinones with arylboronic acids
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The arylation of C-H bonds to generate heteroaryl-aryl (Het-Ar) and arylated quinone (Quin-Ar) compounds has received great attention to achieve sustainable goals in synthetic chemistry. Despite significant advances, arylation of a broad range of Het-Ar and Quin-Ar derivatives remains a challenging task. Herein, a variety of heterocycles are arylated by using arylboronic acids in the presence of catalytic amounts of inexpensive Fe(NO 3)3. The C-arylated quinone compounds can be prepared by reacting arylboronic acids with either quinone or hydroquinone. The present method is operationally simple, scalable, does not require prefunctionalization of the heterocycle or quinone, and can tolerate a wide variety of functional groups in the coupling partners. These qualities are expected to render this method attractive for academic and industrial use. Direct C-H arylation of a variety of heterocycles and quinones with arylboronic acids has been developed. An inexpensive iron catalyst, Fe(NO3)3, and a co-oxidant, persulfate, were used in air. The protocol is applicable for large-scale synthesis and is expected to find application as a result of its operational simplicity. Copyright
- Deb, Arghya,Manna, Srimanta,Maji, Arun,Dutta, Uttam,Maiti, Debabrata
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supporting information
p. 5251 - 5256
(2013/09/02)
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- Iron-catalyzed cross-coupling of electron-deficient heterocycles and quinone with organoboron species via innate C-H functionalization: Application in total synthesis of pyrazine alkaloid botryllazine A
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Here, we report an iron-catalyzed cross-coupling reaction of electron-deficient heterocycles and quinone with organoboron species via innate C-H functionalization. Iron(II) acetylacetonate along with oxidant (K 2S2O8) and phase-transfer catalyst (TBAB) under open flask conditions efficiently catalyzed the cross-coupling of pyrazine with arylboronic acids and gave monoarylated products in good to excellent yields. Optimized conditions also worked for other heterocylces such as quinoxalines, pyridines, quinoline, and isoquinoline as well as quinones. In addition, we demonstrated as a first example its application for the synthesis of anticancer marine pyrazine alkaloid botryllazine A.
- Singh, Parvinder Pal,Aithagani, Sravan Kumar,Yadav, Mahipal,Singh, Varun Pratap,Vishwakarma, Ram A.
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p. 2639 - 2648
(2013/04/24)
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- The direct arylation of benzoquinones with arylboronic acid promoted by iron(II) oxalate
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Arylations of various quinones with several arylboronic acids have been developed. The reactions proceed readily at ambient temperature using iron(II) oxalate as a catalyst and potassium persulfate as a co-oxidant. The mechanism is presumed to proceed through a nucleophilic radical addition to the quinone with in situ reoxidation of the resulting dihydroquinone.
- Huanga, Yibo,Guanb, Dan
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p. 649 - 651
(2014/01/17)
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- FeSO4-promoted direct arylation of benzoquinones with ArB(OH)2 or ArBF3K
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FeSO4·7H2O was proven to work as effective promoter for the direct arylation of benzoquinones with aryl boronic acids in the presence of K2S2O8. In the arylation, slow addition of iron solution was crucial to efficiently proceed with the reaction. Interestingly, the Fe-mediated arylation could be converted into a catalytic reaction by using hydroquinones, instead of benzoquinones, or addition of ascorbic acid.
- Komeyama, Kimihiro,Kashihara, Tetsuya,Takaki, Ken
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supporting information
p. 1084 - 1086
(2013/04/10)
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- Quinones synthesis via hydrogen peroxide oxidation of dihydroxy arenes catalyzed by homogeneous and macroporous-polymer-supported ruthenium catalysts
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Ruthenium(II)/dimethyl phenyloxazoline (Ru(II)/dm-Pheox) complex 2a and its macroporous-polymeric-catalyst 4 were found to be very rapid and efficient catalysts in the hydrogen peroxide oxidation of 1,2- and 1,4-dihydroxy arenes. Most of the quinone products were delivered in 99% yield. The polymeric-catalyst 4 could be reused at least five times.
- Abu-Elfotoh, Abdel-Moneim,Tsuzuki, Kazuyuki,Nguyen, Tram Bao,Chanthamath, Soda,Shibatomi, Kazutaka,Iwasa, Seiji
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p. 8612 - 8617
(2013/09/12)
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- Tandem oxidation-oxidative C-H/C-H cross-coupling: Synthesis of arylquinones from hydroquinones
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A concise and efficient approach to arylquinones from widely available hydroquinones has been developed through a tandem reaction involving the oxidation of hydroquinones and subsequent oxidative C-H/C-H cross-coupling of the resulting quinones with arenes.
- Zhang, Shuai,Song, Feijie,Zhao, Dongbing,You, Jingsong
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supporting information
p. 4558 - 4560
(2013/06/04)
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- Iron-mediated direct arylation with arylboronic acids through an aryl radical transfer pathway
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A novel iron-mediated direct C-H arylation of quinones and pyridine analogues with arylboronic acids has been developed using dichloromethane and water as solvents at ambient temperature. FeS is employed and serves as an efficient catalyst. A detailed reaction mechanism is speculated and expounded.
- Wang, Jian,Wang, Shan,Wang, Gao,Zhang, Ji,Yu, Xiao-Qi
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supporting information
p. 11769 - 11771
(2013/01/15)
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- μ-oxo-bridged hypervalent iodine(III) compound as an extreme oxidant for aqueous oxidations
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We have found that in aqueous oxidations the -oxo-bridged hypervalent iodine trifluoroacetate reagent 1 {[(PhI(OCOCF]} is generally more reactive than the corresponding monomeric reagent, especially toward phenolic substrates. -Oxo-bridged 1 in aqueous media thus provided dearomatized quinones 3 in excellent yields in most cases compared to conventional phenyliodine(III) diacetate and bis(trifluoroacetate), as a result of the rapid oxidation of both phenols and naphthols 2. Furthermore, the oxidation reactions proceeded even in water using water-soluble -oxo oxidant 1, which has promise for -oxo-bridged reagent 1 to become the favored reagent over hydrophobic phenyliodine(III) diacetate and bis(trifluoroacetate). Georg Thieme Verlag Stuttgart New York.
- Dohi, Toshifumi,Nakae, Tomofumi,Takenaga, Naoko,Uchiyama, Teruyoshi,Fukushima, Kei-Ichiro,Fujioka, Hiromichi,Kita, Yasuyuki
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experimental part
p. 1183 - 1189
(2012/05/19)
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- Practical C-H functionalization of quinones with boronic acids
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A direct functionalization of a variety of quinones with several boronic acids has been developed. This scalable reaction proceeds readily at room temperature in an open flask using inexpensive reagents: catalytic silver(I) nitrate in the presence of a persulfate co-oxidant. The scope with respect to quinones is broad, with a variety of alkyl- and arylboronic acids undergoing efficient cross-coupling. The mechanism is presumed to proceed through a nucleophilic radical addition to the quinone with in situ reoxidation of the resulting dihydroquinone. This method has been applied to complex substrates, including a steroid derivative and a farnesyl natural product.
- Fujiwara, Yuta,Domingo, Victoriano,Seiple, Ian B.,Gianatassio, Ryan,Del Bel, Matthew,Baran, Phil S.
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supporting information; experimental part
p. 3292 - 3295
(2011/05/03)
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- Ruthenium-catalyzed oxidative dearomatization of phenols to 4-(tert-butylperoxy)cyclohexadienones: Synthesis of 2-substituted quinones from p-substituted phenols
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The ruthenium-catalyzed oxidation of phenols with tert-butylhydroperoxide efficiently gives the corresponding 4-(tert-butylperoxy)cyclohexadienones. The oxidation proceeds selectively because of ruthenium's ability for rapid single-electron transfer. This biomimetic oxidation reaction is highly useful to obtain the metabolic compounds desired for confirming the safety of medicines and related compounds. Typically, the first metabolic compound of the female hormone estrone is readily obtained by this biomimetic oxidation reaction. The resulting 4-(tert-butylperoxy)cyclohexadienones are versatile synthetic intermediates, which can be transformed into 2-substituted 1,4-benzoquinones by treatment with acid catalysts. Acid-promoted rearrangement followed by a Diels-Alder reaction provides a new strategy for the synthesis of fused cyclic compounds, such as naphthoquinone and anthraquinone derivatives, from readily available phenols. The nonnatural 1,4-diacetoxy steroidal skeleton is obtained by the oxidation of estrone followed by zinc-mediated migration. Vitamin K 3 is synthesized selectively from p-cresol in an overall 79 % yield in 4 steps, and the synthesis includes the ruthenium-catalyzed oxidation.
- Murahashi, Shun-Ichi,Miyaguchi, Noriko,Noda, Shinji,Naota, Takeshi,Fujii, Akiko,Inubushi, Yasutaka,Komiya, Naruyoshi
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scheme or table
p. 5355 - 5365
(2011/11/14)
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- Synthesis of 2-substituted quinones, vitamin K3, and vitamin K1 from p-cresol. BF3·OEt2-catalyzed methyl migration of 4-tert-butyldioxycyclohexadienones
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BF3·OEt2-catalyzed methyl group migration of 4-methyl-4-tert-butyldioxycyclohexadienone, which is obtained by ruthenium-catalyzed oxidation of p-cresol with tert-butyl hydroperoxide, in hexafluoro-2-propanol/toluene gave toluquinone efficiently. The reaction can be applied to the regio-selective short-step syntheses of vitamin K3 and vitamin K1 from p-cresol.
- Murahashi, Shun-Ichi,Fujii, Akiko,Inubushi, Yasutaka,Komiya, Naruyoshi
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scheme or table
p. 2339 - 2341
(2010/05/19)
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- Synthesis of 2,5-Diaminoquinones by one-pot copper-catalyzed aerobic oxidation of hydroquinones and addition reaction of amines
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The aerobic oxidation of various hydroquinones was achieved by using copper nanoparticles entrapped in aluminum oxyhydroxide [Cu/ AlO(OH)] at room temperature. Furthermore, 2,5diamino-1,4-benzoquinones were synthesized directly from hydroquinone and amines by a one-pot procedure consisting of the copper-catalyzed aerobic oxidation of hydroquinones and the double addition of amines to the resulting quinones.
- Kim, Sungjin,Kim, Daehwan,Park, Jaiwook
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experimental part
p. 2573 - 2578
(2009/12/29)
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- Polymer incarcerated gold catalyzed aerobic oxidation of hydroquinones and their derivatives
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Polymer-incarcerated gold (PI Au) cluster catalysts mediated aerobic oxidation of hydroquinones and catechols to quinones very efficiently under mild conditions. The characteristic role of water in the reaction system was also observed. Copyright
- Miyamura, Hiroyuki,Shiramizu, Mika,Matsubara, Ryosuke,Kobayashi, Shu
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p. 360 - 361
(2008/09/20)
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- Aerobic oxidation of hydroquinone derivatives catalyzed by polymer-incarcerated platinum catalyst
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(Chemical Equation Presented) It's a lock-in! A remarkably wide substrate scope of hydroquinones are oxidized to quinones in high yields in a platinum-catalyzed process with as low as 0.05 mol% catalyst. The aerobic oxidation is catalyzed by platinum nanoclusters trapped in a styrene-based polymer network (see scheme, PI Pt=polymer-incarcerated nanoclusters). The catalyst could be reused at least 13 times without any loss of catalytic activity.
- Miyamura, Hiroyuki,Shiramizu, Mika,Matsubara, Ryosuke,Kobayashi, Shu
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supporting information; experimental part
p. 8093 - 8095
(2009/04/13)
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- A rapid and efficient synthesis of quinone derivatives: Ru(II)-or Ir(I)-catalyzed hydrogen peroxide oxidation of phenols and methoxyarenes
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Hydroquinone and methoxybenzene derivatives were catalytically oxidized promptly to the corresponding quinones in up to 99% yield. With a catalyst loading of 0.01 mol %, a maximum TON of 8.4 × 103 was attained in the case of Ru(II)-complex. Ru(II)(pybox-dh)(pydic) is able to enhance the hydrogen peroxide oxidation of substituted hydroquinones as well as methoxybenzenes, but Ir[(coe)2Cl]2 and Ir[(cod)Cl] 2 were found to be effective catalysts only for the former substrates under similar oxidation conditions.
- Iwasa, Seiji,Fakhruddin, Ahmad,Widagdo, Herman Setyo,Nishiyama, Hisao
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p. 517 - 520
(2007/10/03)
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- Photoreduction of p-Benzoquinones: Effects of Alcohols and Amines on the Intermediates and Reactivities in Solution
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The photochemistry of 1,4-benzoquinone (BQ) and alkyl-, Cl- and related derivatives, e.g. methyl-, 2,6-dimethyl-, chloro-, 2,5-dichloro-1,4-benzoquinone, duroquinone and chloranil, was studied in nonaqueous solvents by UV-vis spectroscopy using nanosecond laser pulses at 308 nm. The reactivity of the triplet state (3Q*) of the quinones with 2-propanol in the absence of water is largest for BQ and depends mainly on the quinone structure, whereas the rate constant of electron transfer from amines, such as triethylamine (TEA) or 1,4-diazabicyclo[2.2.2]octane, is close to the diffusion-controlled limit for BQ and most derivatives. Photoinduced charge separation after electron transfer from amines to 3Q* and the subsequent charge recombination or neutralization are supported by time-resolved conductivity measurements. The half-life of the decay kinetics of the semiquinone radical (.QH/Q.-) depends significantly on the donor and the medium. The photoconversion into the hydroquinones was measured under various conditions, the quantum yield, λirr = 254 nm, increases with increasing 2-propanol and TEA concentrations. The effects of quenching of 3Q*, the .QH/Q.- radicals and the photoconversion are outlined. The mechanisms of photoreduction of quinones in acetonitrile by 2-propanol are compared with those by TEA in benzene and acetonitrile, and the specific properties of substitution are discussed.
- Goerner, Helmut
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p. 440 - 448
(2007/10/03)
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- Aerobic oxidation of hydroquinones to quinones catalyzed by VO(acac)2
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In the presence of a catalytic amount of VO(acac)2, oxidation of hydroquinone and its derivatives with molecular oxygen at room temperature gave the corresponding quinones in moderate to high yields.
- Hwang, Der-Ren,Chu, Chang-Ying,Wang, Sheng-Kai,Uang, Biing-Jiun
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- Rapid conversion of phenols to p-benzoquinones under acidic conditions with lead dioxide
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Treatment of 4-unsubstituted and 4-halogenated phenols with PbO2 and 70% HClO4 in AcOH afforded the corresponding p-benzoquinones in fair to high yields. The oxidation of 4-substituted 2,6-di-tertbutylphenols 6 with PbO2 and 70% HClO4 in acetone gave 2,6-di-tert-butyl-p-benzoquinone (2).
- Omura, Kanji
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p. 1145 - 1148
(2007/10/03)
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- Catalytic Activities of CuSO4/Al2O3 in Dehydrogenation of Arenes by Dioxygen
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The oxidation reactions of hydroquinones, 2-naphthols, or 2,6-di-tert-butylphenol efficiently occurred by catalysis with alumina-supported copper(II) sulfate to give the corresponding benzoquinones, 1,1'-bi-2-naphthols, and 4,4'-diphenoquinone, respectively, in good yields.The synthetic potentiality of the catalytic reactions was demonstrated by easy isolation of the final products using only filtration and solvent evaporation as well as by application to large-scale syntheses of the benzoquinones and binaphthols.The catalysis with alumina-supported copper(II) sulfate was also applied to the oxidative intramolecular coupling of 5,5'-diacenaphthene to the corresponding perylene compound.
- Sakamoto, Takaaki,Yonehara, Hisatomo,Pac, Chyongjin
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p. 3194 - 3199
(2007/10/03)
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- Redox reactions of phenylhydroquinone with quinones in water
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The reversible reaction of hydrogen transfer between phenylhydroquinone and quinones (p-benzo-quinone, chlorobenzoquinone, and methylbenzoquinone) was studied as depending on water pH and composition and the procedure for water pretreatment. A spectrophotometric technique for measuring low concentrations of phenylbenzoquinone produced in the reaction was developed, and the rate constants for the forward and back reactions and the equilibrium constants were calculated. The reaction rate increased drastically (by more than 4 orders of magnitude) as pH grew from 4 to 8. The dependence of the reaction rate in water on pH was explained by the formation of hydroquinone anions in the alkaline region. These anions are strong electron donors and readily react with quinone molecules. The mechanism of the redox reaction in the hydroquinone-p-benzoquinone system is considered in quantum-chemical terms.
- Kalnin'sh,Pavlova
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p. 1596 - 1600
(2007/10/03)
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- Persulfate/copper(II): A mild and efficient oxidising system for the conversion of dihydroxybenzenes to quinones
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Sodium persulfate in the presence of copper(II) ions efficiently oxidises a number of o- and p-diphenols to the corresponding quinones under mild conditions.
- Costantini,D'Ischia,Prota
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p. 1399 - 1400
(2007/10/02)
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- Synthons for the Parent Vinyl Carbene Complex in the Benzannulation Reaction
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The benzannulation reaction of Fischer carbene complexes with alkynes to produce phenols was found not be synthetically useful for the parent vinyl carbene complex 6a.The β-silylated vinyl carbene complex 6c is more stable than the parent vinyl complex 6a and can be effectively used as a synthon for 6a since during the benzannulation the silicon migrates to the phenol function preferentially over hydrogen to give the arene chromium tricarbonyl complexes of the type 19.This reaction is general for a number of alkynes that have incorporated important functionality and is more useful for terminal alkynes than for internal alkynes.The migration of the silicon is responsible for the fact that stable arene chromium tricarbonyl complexes can be isolated from these reactions and makes possible transformations that take advantage of the activating ability of the chromium tricarbonyl group.This is demonstrated in intramolecular aromatic nucleophilic additions reactions.It is also shown in a single example that the α-silylated vinyl carbene complex 10b can in principle also serve as a synthon for the parent vinyl carbene complex 6a, since the benzannulated product can be disilylated with trifluoroacetic acid.
- Chamberlin, Steven,Wulff, William D.
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p. 3047 - 3054
(2007/10/02)
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- Arylation of quinones with aryl mercuryl chloride catalyzed by lithium palladium chloride
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Treatment of benzoquinone/naphthoquinone with aryl mercury chloride in the presence of palladium chloride and lithium chloride gives the corresponding aryl substituted benzoquinone/naphthoquinone at the quinonoid position.
- Singh,Rohtagi,Khanna
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p. 987 - 993
(2007/10/02)
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- Reactive dyestuffs
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Triphendioxazine reactive dyestuffs of the general formula STR1 with the substituent definition given in the description, are outstandingly suitable for dyeing and printing materials containing hydroxyl groups or amide groups. They give red dyeings with high wet- and light-fastnesses.
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- Reduction of Arenediazonium Salts by Hydroquinone. Kinetics and Mechanism for the Electron-Transfer Step
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Arenediazonium tetrafluoroborate salts undergo facile electron transfer reaction with hydroquinone in aqueous phosphate-buffered solutions containing the hydrogen donor solvent acetonitrile.Reaction rates are the first-order in hydroquinone and arenediazonium ion concentrations, and they exhibit inverse first order dependence on the hydrogen ion concentration over the pH range of 1.0-9.5.Benzoquinone and arene are the principial products, but arylation of acetonitrile and benzoquinone are competitive in a reaction process that exhibits a 2:1 stoichiometric relationship between the arenediazonium ion salt and hydroquinone.Rate constants for reduction of substituted benzediazonium ions by the monoanion of hydroquinone correlate with ? constants yielding a ρ value of 3.5.Reactions performed in deuterium oxide show kinetic isotope effects that reflect the solvent isotope effect on the acidity constant for hydroquinone, and levels of isotope incorporation by deuterium abstraction from deuterium oxide and/or acetonitrile-d3 demonstrate that neither water nor hydroquinone are hydrogen atom donors to intermediate aryl radicals.Reduction of arenediazonium ions involves a rate-limiting single electron transfer from the monoanion of hydroquinone followed by a rapid single electron transfer from the semiquinone intermediate to the diazonium ion.Application of Marcus theory provides calculated rate constants for electron transfer from the hydroquinone monoanion to arenediazonium ions.These rate constants, together with the absence of evidence for a diazo ether intermediate and rate constants for diazotate formation, suggest that electron transfer occurs by an outer-sphere mechanism.
- Brown, Kathlynn C.,Doyle, Michael P.
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p. 3255 - 3261
(2007/10/02)
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- FUNCTIONAL GROUP OXIDATION USING SODIUM PERBORATE
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Sodium perborate in acetic acid is an effective reagent for the oxidation of anilines to nitroarenes and of sulphides to either sulphoxides or sulphones.It is also an excellent reagent for the oxidative deprotection of ketone dimethylhydrazones.Baeyer-Villiger oxidation of ketones can be carried out with sodium perborate in either trifluoroacetic acid or acetic acid/trifluoroacetic acid mixtures, and hydroquinones and certain highly substituted phenols are smoothly converted into quinones.
- McKillop, Alexander,Tarbin, Jonathan A.
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p. 1753 - 1758
(2007/10/02)
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- Triphendioxazine dyestuffs
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Triphendioxazine dyestuffs of the formula STR1 having the substituent meanings specified in the descriptive part, are highly suitable for dyeing and printing hydroxyl- or amido-containing materials, in particular fibre materials, and produce wash-fast dyeings and prints.
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- Oxidative Coupling of Quinones and Aromatic Compounds by Palladium(II) Acetate
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The oxidation of 1,4-benzoquinone, 2-phenyl-1,4-benzoquinone, 1,4-naphthoquinone, and 1,2-naphthoquinone by palladium(II) acetate in acetic acid containing arenes gave the corresponding aryl-sustituted quinones.Treatment of 1,4-naphthoquinone with aromatic heterocycles such as furfural, 2-acetylfuran, methyl 2-furoate, 2-acetylthiophene, 1-(phenylsulfonyl)pyrrole, 1-(phenylsulfonyl)indole, 4-pyrone, and 1-methyl-2-pyridone in the presence of palladium acetate gave the corresponding 2-heteroaryl-substituted 1,4-naphthoquinones.
- Itahara, Toshio
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p. 5546 - 5550
(2007/10/02)
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