- A scalable and green one-minute synthesis of substituted phenols
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A mild, green and highly efficient protocol was developed for the synthesis of substituted phenols via ipso-hydroxylation of arylboronic acids in ethanol. The method utilizes the combination of aqueous hydrogen peroxide as the oxidant and H2O2/HBr as the reagent under unprecedentedly simple and convenient conditions. A wide range of arylboronic acids were smoothly transformed into substituted phenols in very good to excellent yields without chromatographic purification. The reaction is scalable up to at least 5 grams at room temperature with one-minute reaction time and can be combined in a one-pot sequence with bromination and Pd-catalyzed cross-coupling to generate more diverse, highly substituted phenols.
- Elumalai, Vijayaragavan,Hansen, J?rn H.
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p. 40582 - 40587
(2020/11/18)
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- Method for photocatalytic synthesis of polybrominated phenol compound in water phase
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The invention discloses a method for photocatalytic synthesis of a polybrominated phenol compound in a water phase, comprising the following steps: adding a catalytic amount of a radical initiator, aphenol derivative and low-toxic and cheap bromide salt and water into a reaction vessel, reacting at room temperature at 5 W power in a photocatalytic reactor for a certain period, extracting with ethyl acetate and then re-crystallizing to obtain a polybrominated phenol compound. The above radical initiator is eosin, azobisisobutanol, sodium persulfate, ammonium persulfate or potassium persulfate.The free radical initiator and the bromine salt are cheap and easily available, and the method is an ideal synthesis method of the polybrominated phenol compound. According to the method, low-toxicity bromine salt instead of liquid bromine is used to carry out a bromination reaction, unstable and explosive hydrogen peroxide is replaced with the cheap and easily-available free radical initiator, and an emerging photocatalytic method is used. The polybrominated phenol compound can be obtained in a high yield by only using a 5W power lamp for the reaction, the reaction selectivity is high, by-products are less, and the post-treatment is simple.
- -
-
Paragraph 0012-0019
(2019/08/30)
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- Synthesis and antitumor activity evaluation of compounds based on toluquinol
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Encouraged by the promising antitumoral, antiangiogenic, and antilymphangiogenic properties of toluquinol, a set of analogues of this natural product of marine origin was synthesized to explore and evaluate the effects of structural modifications on their cytotoxic activity. We decided to investigate the effects of the substitution of the methyl group by other groups, the introduction of a second substituent, the relative position of the substituents, and the oxidation state. A set of analogues of 2-substituted, 2,3-disubstituted, and 2,6-disubstituted derived from hydroquinone were synthesized. The results revealed that the cytotoxic activity of this family of compounds could rely on the hydroquinone/benzoquinone part of the molecule, whereas the substituents might modulate the interaction of the molecule with their targets, changing either its activity or its selectivity. The methyl group is relevant for the cytotoxicity of toluquinol, since its replacement by other groups resulted in a significant loss of activity, and in general the introduction of a second substituent, preferentially in the para position with respect to the methyl group, was well tolerated. These findings provide guidance for the design of new toluquinol analogues with potentially better pharmacological properties.
- Cheng-Sánchez, Iván,Torres-Vargas, José A.,Martínez-Poveda, Beatriz,Guerrero-Vásquez, Guillermo A.,Medina, Miguel ángel,Sarabia, Francisco,Quesada, Ana R.
-
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- Regioselective monobromination of aromatics via a halogen bond acceptor-donor interaction of catalytic thioamide and N-bromosuccinimide
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Regioselective monobromination of various aromatics was achieved at room temperature using N-bromosuccinimide and 5 mol% of thioamides in acetonitrile. With thiourea as catalyst, activated aromatics, such as anisole, acetanilide, benzamide and phenol analogues containing electron donating or withdrawing groups, were brominated with high regioselectivity. Room temperature brominations of weakly activated aromatics and deactivated 9-fluorenone were accomplished by 5 mol% thioacetamide, higher substrates concentrations and longer reaction times. A backbonding of the bromine lone pairs with the π*of C[dbnd]S group and a halogen bond between the halogen bond donor bromine and the halogen bond acceptor sulfur of the thioamide are thought to be the principal interactions and cause of N-bromosuccinimide activation.
- Bovonsombat, Pakorn,Teecomegaet, Pattaradra,Kulvaranon, Panisanun,Pandey, Aditi,Chobtumskul, Kittithorn,Tungsirisurp, Sireethorn,Sophanpanichkul, Punyanuch,Losuwanakul, Satreerat,Soimaneewan, Dechathon,Kanjanwongpaisan, Patcharida,Siricharoensang, Pornpawit,Choosakoonkriang, Sirirat
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p. 6564 - 6572
(2017/10/17)
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- A quick, mild and efficient bromination using a CFBSA/KBr system
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Bromination is a fundamental transformation in organic chemistry and brominated compounds as building blocks are of paramount importance in organic synthesis. In our study, we have developed an efficient method of bromination by using a CFBSA/KBr system at room temperature in a short reaction time. Notably, this approach has been proven to be applicable to a range of substrates including 1,3-diketones and β-keto esters, phenols, aromatic amines and heteroarenes with good to excellent yields.
- Jiang, Pan-Pan,Yang, Xian-Jin
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p. 90031 - 90034
(2016/10/09)
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- Vanadium bromoperoxidase (VBrPO) mimics: Synthesis, structure and a comparative account of the catalytic activity of newly synthesized oxidovanadium and oxido-peroxidovanadium complexes
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The bioinspired catalytic activities of two newly synthesised vanadium(iv)dioxido (complex 1) and vanadium(v) oxido-peroxido (complex 2) complexes with the neutral tridentate benzimidazole ligand, 2,6-di-(1H-benzo[d]imidazol-2-yl)pyridine (Byim) have been established. The bromoperoxidase activities of these complexes have been established through the activation of C-H bonds of substrates like phenol, o-cresol and p-cresol. The products, characterized by GC analysis shows that good conversions have been achieved. Considering the catalytic efficiency of the complexes, complex 2, with one in-built peroxido group is found to be more potent than complex 1. The catalytic cycles of both the complexes have been established from experimental results.
- Palmajumder, Eshita,Patra, Swarup,Drew, Michael G. B.,Mukherjea, Kalyan K.
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p. 8696 - 8703
(2016/10/13)
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- Preparation of carbazole and dibenzofuran derivatives by selective bromination on aromatic rings or benzylic groups with N-bromosuccinimide
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N-Bromosuccinimide (NBS), a bromine source, has been used to study the bromination of toluidine and cresols systematically to clarify the underlying mechanism and the orientation effect. It has been found that bromination of toluidine and cresols which possess electron-donating NH2/OH with NBS gives electrophilic aromatic substitution products quickly instead of the desired benzylic bromination products. In contrast, when the electronic effect of the substituted groups is reversed, only the benzylic bromination products are gained. Based on this methodology, several potential AChE inhibitors, such as 2-methoxy-5-(benzylamino)methyl-dibenzofuran, 3-bromo-2-methoxy-5-methyl-9H- carbazole, 3,6-dibromo-2-methoxy-5-methyl-9H-carbazole, and 5-(bromomethyl)-2- methoxy-9H-(phenylsulfonyl)-carbazole have been synthesized.
- Fang, Lei,Zhang, Haun,Fang, Xubin,Gou, Shaohua,Cheng, Lin
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p. 635 - 641
(2014/06/23)
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- Synthesis, structural characterization, VHPO mimicking peroxidative bromination and DNA nuclease activity of oxovanadium(v) complexes
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The two novel oxovanadium(v) complexes [VO(PyDC)(BHA)] (1) [PyDC = pyridine-2,6-dicarboxylate, BHA = benzohydroxamate] and [VO(PyDC)(BPHA)] (2) [BPHA = benzophenyl hydroxamate] were synthesized by successive addition of a methanolic solution of H2PyDC and the corresponding hydroxamic acid ligand to the aqueous solution of ammonium metavanadate (NH4VO 3). The hydroxamic acid ligands were characterized by elemental analysis, IR, UV-vis and NMR studies whereas the complexes were characterized by IR, UV-vis, CHN, molar conductance, magnetic moment, mass and NMR spectroscopic methods. The structures of the complexes were determined by single crystal X-ray crystallography. The structures of both complexes reveal that vanadium(v) has distorted octahedral geometry. The bromoperoxidase activities of these complexes have been demonstrated through the activation of C-H bonds of phenol, o-cresol and p-cresol. The catalytic products have been characterized by GC-MS analysis which shows that good conversions have been achieved. So far as the catalytic efficiency of the complexes are concerned complex 2 is found to be superior to complex 1. Both the complexes were tested for DNA nuclease activity with pUC19 plasmid DNA. The results show that both of them exhibited nuclease activity against pUC19 circular plasmid DNA. The complexes produced both nicked coils and linear forms. In this case also it is observed that complex 2 shows better nuclease activity than complex 1.
- Patra, Swarup,Chatterjee, Suparna,Si, Tapan Kr.,Mukherjea, Kalyan K.
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p. 13425 - 13435
(2013/09/23)
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- Vanadate-dependent bromoperoxidases from Ascophyllum nodosum in the synthesis of brominated phenols and pyrroles
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Bromoperoxidases from the brown alga Ascophyllum nodosum, abbreviated as VBrPO(AnI) and VBrPO(AnII), show 41% sequence homology and differ by a factor of two in the percentage of α-helical secondary structures. Protein monomers organize into homodimers for VBrPO(AnI) and hexamers for VBrPO(AnII). Bromoperoxidase II binds hydrogen peroxide and bromide by approximately one order of magnitude stronger than VBrPO(AnI). In oxidation catalysis, bromoperoxidases I and II turn over hydrogen peroxide and bromide similarly fast, yielding in morpholine-4-ethanesulfonic acid (MES)-buffered aqueous tert-butanol (pH 6.2) molecular bromine as reagent for electrophilic hydrocarbon bromination. Alternative compounds, such as tribromide and hypobromous acid are not sufficiently electrophilic for being directly involved in carbon-bromine bond formation. A decrease in electrophilicity from bromine via hypobromous acid to tribromide correlates in a frontier molecular orbital (FMO) analysis with larger energy gaps between the π-type HOMO of, for example, an alkene and the σ*Br,X-type LUMO of the bromination reagent. By using this approach, the reactivity of substrates and selectivity for carbon-bromine bond formation in reactions mediated by vanadate-dependent bromoperoxidases become predictable, as exemplified by the synthesis of bromopyrroles occurring naturally in marine sponges of the genera Agelas, Acanthella, and Axinella. The Royal Society of Chemistry.
- Wischang, Diana,Radlow, Madlen,Hartung, Jens
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p. 11926 - 11940
(2013/09/02)
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- Synthesis and biological evaluation of 1,4-naphthoquinones and quinoline-5,8-diones as antimalarial and schistosomicidal agents
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Improving the solubility of polysubstituted 1,4-naphthoquinone derivatives was achieved by introducing nitrogen in two different positions of the naphthoquinone core, at C-5 and at C-8 of menadione through a two-step, straightforward synthesis based on the regioselective hetero-Diels-Alder reaction. The antimalarial and the antischistosomal activities of these polysubstituted aza-1,4-naphthoquinone derivatives were evaluated and led to the selection of distinct compounds for antimalarial versus antischistosomal action. The AgII-assisted oxidative radical decarboxylation of the phenyl acetic acids using AgNO3 and ammonium peroxodisulfate was modified to generate the 3-picolinyl-menadione with improved pharmacokinetic parameters, high antimalarial effects and capacity to inhibit the formation of β-hematin. The Royal Society of Chemistry 2012.
- Lanfranchi, Don Antoine,Cesar-Rodo, Elena,Bertrand, Beno?t,Huang, Hsin-Hung,Day, Latasha,Johann, Laure,Elhabiri, Mourad,Becker, Katja,Williams, David L.,Davioud-Charvet, Elisabeth
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scheme or table
p. 6375 - 6387
(2012/09/05)
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- Cu-Mn spinel oxide catalyzed regioselective halogenation of phenols and N-heteroarenes
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A novel simple, mild chemo- and regioselective method has been developed for the halogenation of phenols using Cu-Mn spinel oxide as a catalyst and N-halosuccinimide as halogenating agent. In the presence of Cu-Mn spinel oxide B, both electron-withdrawing and electron-donating groups bearing phenols gave monohalogenated products in good to excellent yields with highest para-selectivity. The para-substituted phenol gave monohalogenated product with good yield and ortho-selectivity. N-Heteroarenes such as indoles and imidazoles also gave monohalogenated products with high selectivity. Unlike the copper-catalyzed halogenation, the present method works well with electron-withdrawing group bearing phenols and gives comparatively better yields and selectivity. The Cu-Mn spinel catalyst is robust and reused three times under optimized conditions without any loss in catalytic activity. Nonphenolics did not undergo this transformation.
- Singh, Parvinder Pal,Thatikonda, Thanusha,Kumar, K. A. Aravinda,Sawant, Sanghapal D.,Singh, Baldev,Sharma, Amit Kumar,Sharma,Singh, Deepika,Vishwakarma, Ram A.
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scheme or table
p. 5823 - 5828
(2012/09/05)
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- Biomimetic synthesis of (-)-pycnanthuquinone C through the diels-alder reaction of a vinyl quinone
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Three strikes and you're out! A concise, asymmetric synthesis of pycnanthuquinone C underscores the biosynthetic relevance of Diels-Alder reactions of vinyl quinones. The relative and absolute configuration of the natural product has been elucidated.
- Loebermann, Florian,Mayer, Peter,Trauner, Dirk
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supporting information; experimental part
p. 6199 - 6202
(2010/11/18)
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- 1-Benzyl-4-aza-1-azoniabicyclo[2.2.2]octane tribromide as a regenerable and useful reagent for bromination of phenols under mild conditions
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1-Benzyl-4-aza-1-azoniabicyclo[2.2.2]octane tribromide has been examined over several phenolic compounds under mild conditions. The reaction gives brominated phenols in good to excellent yields. Straightforward work-up of the reaction yields pure products in several cases.
- Hajipour, Abdol R.,Pourmousavi, Seied A.,Ruoho, Arnold E.
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p. 796 - 800
(2007/10/03)
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- Site directed nuclear bromination of aromatic compounds by an electrochemical method
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Direct bromination of a wide range of aromatic compounds possessing electron-donating groups, such as methoxy, hydroxy or amino groups, have been carried out by two-phase electrolysis. This electrochemical method results in high yields (70-98%) of monobromo compounds and usually with high regioselectivity (>95%) for the para position.
- Raju,Kulangiappar,Anbu Kulandainathan,Uma,Malini,Muthukumaran
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p. 4581 - 4584
(2007/10/03)
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- A stereocontrolled synthesis of δ-trans-tocotrienoloic acid
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(Chemical Equation Presented) A consise stereoselective total synthesis of a naturally occurring polymerase β inhibitor, δ-trans-tocotrienoloic acid (2), is described. The key step in the synthesis is an acid-catalyzed cyclodehydration reaction. Additiona
- Maloney, David J.,Hecht, Sidney M.
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p. 4297 - 4300
(2007/10/03)
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- A controlled and selective bromination of phenols by benzyltriphenylphosphonium tribromide
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Reactions of phenols with benzyltriphenylphosphonium tribromide in dichloromethane-methanol mixture (2:1) gave mono, di and tri brominated phenols at room temperature with high selectivity and good yields.
- Hajipour, Abdol Reza,Mallakpour, Shadpour E.,Imanieh, Hossein,Pourmousavi, Seied A.
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p. 272 - 275
(2007/10/03)
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- An efficient and regioselective oxybromination of aromatic compounds using potassium bromide and oxone
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A simple, efficient and regioselective method for oxybromination of aromatics is reported. The electrophilic substitution of bromine generated in situ from potassium bromide using oxone as an oxidant for the first time.
- Narender,Srinivasu,Ramakrishna Prasad,Kulkarni,Raghavan
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p. 2313 - 2318
(2007/10/03)
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- Amines substituted with a dihydro-benzofuranyl or with a dihydro-isobenzofuranyl group, an aryl or heteroaryl group and an alkyl group, having retinoid-like biological activity
-
Compounds of Formula 1 and of Formula 2 where the symbols have the meaning defined in the specification, have retinoid-like biological activity.
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-
- Transition metal-catalyzed oxidations. 11 : Para-selective chlorination and bromination of phenols with tert-butyl hydroperoxide and TiX(OiPr)3
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Mononuclear phenols 1-4 are chlorinated or brominated with high para-selectivity and in good yields to the halides 5-11 with the TiXn(OiPr)m/TBHP system (X = Cl or Br). WILEY-VCH Verlag GmbH, 1999.
- Krohn, Karsten,Rieger, Hagen,Steingroever, Klaus,Vinke, Ingeborg
-
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- 1,3-dibromo-5,5-dimethylhydantoin, a useful reagent for aromatic bromination
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1,3-dibromo-5,5-dimethylhydantoin (DBDMH) is a useful and easy to handle reagent for bromination of various aromatic derivatives substituted with electron donating groups. In the presence of trimethylsilyltrifluoromethanesulfonate, DBDMH showed increased reactivity, and in one case, the reaction followed another pathway, suggesting an alternative mechanism.
- Chassaing, Christophe,Haudrechy, Arnaud,Langlois, Yves
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p. 4415 - 4416
(2007/10/03)
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- 4,4-Dibromo-3-methylpyrazol-5-one: New applications for selective monobromination of phenols and oxidation of sulfides to sulfoxides
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Dibromopyrazolone 1, a stable, crystalline solid effects para selective monobromination of phenols and aniline substrates under mild conditions. Selective oxidation of sulfides to sulfoxides can also be accomplished by using 1 in high yields.
- Mashraqui, Sabir H.,Mudaliar, Chandrashekar D.,Hariharasubrahmanian, Harini
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p. 4865 - 4868
(2007/10/03)
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- A new mild and selective reagent for nuclear bromination
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Hexamethylene tetramine tribromide HMTAHBr3 - a new, mild and regioselective brominant is reported for bromination of aromatic hydrocarbons, substituted ethers, phenols and anilides in high yields.
- Bisarya,Rao
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p. 779 - 788
(2007/10/02)
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- Halogenation Using N-Halogenocompounds. I. Effect of Amines on ortho-Bromination of Phenols with NBS
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Primary and secondary amines, especially diisopropylamine and dibutylamine, catalyzed ortho-dibromination of phenol and ortho-monobromination of 2-substituted phenols with NBS in dichloromethane to give selectively 2,6-dibromophenol and 2-bromo-6-sybstituted phenols, respectively.The effective intermediates are inferred to be N-bromoamines.The scope and limitations of the bromination are also presented.
- Fujisaki, Shizuo,Eguchi, Hisao,Omura, Atsushi,Okamoto, Atsushi,Nishida, Akiko
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p. 1576 - 1579
(2007/10/02)
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- Synthesis and inhibitory activity of bromoquinone derivatives
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2,5 Dibromo-3-methyl-6-isopropyl-1,4-benzoquinone has been reported inhibitory to b6-f and b-c1 complexes [Malkin, R. (1977) Biochim. Biophys. Acta., 501, 552-554]. In this paper, four classes of the analogues are synthesized. They were 5-bromo-3-methyl, 3-bromo-2-methoxy-5-methyl, 2,5-dibromo-3-methyl, and 3,5-dibromo-2-methyl derivatives with the side chain -(CH2)nH of N=5,7,9,11 and 13 at position 6. Dibromo compounds are usually more inhibitory in the mitochondrial ubiquinol cytochrome c reductase; the maximal inhibition was usually with 9 methylene in a functional group.
- Gu, Lianquan,Liu, Cuihua,Xu, Jingxing,King, Tsoo E.
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p. 3199 - 3210
(2007/10/02)
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- SYNTHESIS AND STRUCTURE REVISION OF BIFURCARENONE, A UNIQOE MONOCYCLIC DITERPENE IN COMBINATION WITH A HYDROQUINONE C7 UNIT AS AN INHIBITOR OF MITOTIC CELL DIVISION
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Bifurcarenone, a C27 hydroquinone isolated from the brown seaweed Bifurcaria galapegensis, was synthesized as its racemate, and shown to be 2.The structure 1, originally proposed for bifurcarenone, was synthesized, and found to be different from the natur
- Mori, Kenji,Uno, Tetsuyuki
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p. 1945 - 1958
(2007/10/02)
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- Halogenation Using Quaternary Ammonium Polyhalides. IV. Selective Bromination of Phenols by Use of Tetraalkylammonium Tribromides
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Reaction of phenols with calculated amounts of benzyltrimethylammonium tribromide or tetrabutylammonium tribromide in dichloromethane-methanol for 0.5-1 h under mild conditions gave, selectively, the objective mono-, di-, or tribromophenols in good yields.
- Kajigaeshi, Shoji,Kakinami, Takaaki,Okamoto, Tsuyoshi,Nakamura, Hiroko,Fujikawa, Masahiro
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p. 4187 - 4189
(2007/10/02)
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- Effects of Halogen Substiution on Reactions of o-Quinol Acetates with Isopropylmagnesium Bromide and Diisopropylmagnesium. Competition between Unimolecular Decomposition and Bimolecular Reactions of Radical Anions
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When a single methyl substituent at C-2 or C-4 of an o-quinol acetate (1) is replaced by a halogen atom, a greatly decreased yield of the corresponding 3-isopropylphenol is obtained from reaction of 1 with isopropylmagnesium bromide.Replacement of a second methyl group by halogen results in a marked increase in the yield of the 3-isopropylphenol.Essentially identical product distributions are obtained from reactions of halogenated o-quinol acetates with concentrated and dilute Grignard solutions and with diisopropylmagnesium, in contrast to reactions with halogen-free o-quinol acetates.Reactions with hexadeuterioisopropylmagnesium bromide gave reduction products bearing increasing percentages of deuterium at C-3 as the number of bromines on the rings of the ω-quinol acetates increased.These data are consistent with reactions of halogenated o-quinol acetates, in contrast to those of halogen-free analogues, proceeding solely by SET processes.The reactions of halogen-stabilized radical anions with isopropyl radicals compete with decomposition of radical anions to phenoxy radicals.
- Miller, Bernard,Haggerty, John G.
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p. 174 - 179
(2007/10/02)
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- Reactions of Halogenated o-Quinol Acetates with Isopropylmagnesium Bromide and Di-isopropylmagnesium. Mechanism for Formation of Ethers, Reduction Products, and m-Isopropylphenols
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A mechanism is proposed to account for the nature and the variations in yields of products from reactions of Grignard reagents with halogenated o-quinol acetates.
- Miller, Bernard,Haggerty, John G.
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p. 1617 - 1619
(2007/10/02)
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- Electrophilic Substitution with Rearrangement. Part 10. Some Products of Bromination of 2,4-Dimethylphenol and of 4-t-Butyl-2-methylphenol
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The reaction of 2,4-dimethylphenol with bromine gives first 6-bromo-2,4-dimethylphenol, which according to the conditions of further bromination can give 4,6-dibromo-2,4-dimethylcyclohexa-2,5-dienone; a mixture of 5,6- with some 3,6-dibromo-2,4-dimethylphenol; 6-bromo-4-bromomethyl-2-methylphenol with none of the 2-bromomethyl-4-methyl isomer; or a mixture from which 6-bromo-2,4-bis(bromomethyl)phenol can be isolated.The corresponding dienone from 6-bromo-4-t-butyl-2-methylphenol reacts by more complex pathways, and the products include those of de-t-butylation.The probable mechanisms involved in these reactions are discussed.
- Brittain, Judith M.,Mare, Peter B. D. de la,Newman, Paul A.,Chin, Wong See
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p. 1193 - 1198
(2007/10/02)
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- Electrophilic Substitution with Rearrangement. Part 9. Dienones derived from Brominations of o-, m-, and p-Cresol
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Regiospecific protodebromination of ring-substituted bromophenols derived from 2-, 3-, or 4-methylphenol can be effected by heating them with aqueous hydrogen iodide; the synthetic scope of this reaction has been explored.These di- and poly-bromophenols can generally be converted by further bromination in aqueous acetic acid into dienones , which have now been shown to have the 4-bromo-2,5-dienone rather than the 2-bromo-3,5-dienone structure.The rearrangemens of these dienones to ring-substituted polybromophenols by treatment with sulfuric acid have been investigated; where more than one product is formed, the regioselectivity differs from that prevailing in the corresponding direct bromination of the phenol with liquid bromine.The alternative rearrangements of these dienones in aprotic solvents with and without illumination have been compared with results obtained by reaction of methylphenols with bromine under the same conditions.Characteristic differences between the behaviours of 2-, 3-, and 4-methyl-substituted compounds reflect the specific reactions available to the particular dienones.
- Brittain, Judith M.,Mare, Peter B. D. de la,Newman, Paul A.
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- 5-Cyano-2,3-dihydrobenzofurans useful as herbicides
-
The invention provides herbicidally-active 2,3-dihydro-5-cyanobenzofurans of the formula: STR1 (wherein: R1 and R2 together represent =O or R1 represents hydrogen and R2 represents hydrogen, hydroxy, alkoxy, acyloxy, alkoxycarbonyloxy, alkylthiocarbonyloxy, halogen, isothiocyanato, amino, alkylamino, dialkylamino, arylamino, acylamino, alkoxycarbonylamino, alkylthiocarbonylamino, N-bonded heterocyclyl, cyano or alkylthio; R3 and R4 together represent alkylene or each represent hydrogen or alkyl; and R5, R6 and R7, which may be the same or different, each represent hydrogen, halogen, alkyl, alkoxy, acyl or cyano), processes for their preparation and herbicidal compositions containing them.
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- Reactions of Alkyl-lithium Compounds with Aryl Halides
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Reation of methyl-lithium with tribromophenols and with other aryl polyhalides leads directly to bi- and tri-aryl products. para-Substituents (Y) of 2,6-dibromo-4-Y-phenols promote arylation of substrates by their own lithiation products as Y becomes more electron-withdrawing.An aryne epoxide is not an intermediate in these reactions. 2,4,6-Tribromo-Z-benzenes react to form coupling products when Z can co-ordinate to an introduced ortho-lithium atom or when Z can be directly lithiated.Dimeric aggregation of the organolithium intermediates occurs so as to favor coupling to halogenated substrates.Both polar (ionic) and free-radical pathways are involved.
- Huddle, Penelope A.,Perold, Guido W.
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p. 2617 - 2625
(2007/10/02)
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