- HALOGENATED PHLOROGLUCINOLS FROM RHABDONIA VERTICILLATA
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Six bromo- and/or chloro- derivatives of phloroglucinol have been obtained from the red alga Rhabdonia verticillata.Key Word Index - Rhamdonia verticillata; Rhambdoniaceae; halogenated phenols; bromo- and chlorophloroglucitols.
- Blackman, Adrian J.,Matthews, David J.
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- Transition metal-free protodecarboxylation of electron rich aromatic acids under mild conditions
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A mild and practical method for the transition metal-free protodecarboxylation of aromatic acids using readily available and safe sodium persulfate as initiator was described. This environment-friendly decarboxylation approach was performed at 60 °C in ethanol and could easily scale up to the gram level with a good yield. In Particular, the tandem reactions of decarboxylation and halogenation were achieved by the addition of the corresponding halogenating reagents to the reaction system.
- Fang, Jingxian,Wang, Dangui,Deng, Guo-Jun,Gong, Hang
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p. 4503 - 4506
(2017/10/30)
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- Oxidative bromination reactions in aqueous media by using Bu4NBr/TFA/H2O2 system
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Metal-free oxidative bromination reactions in aqueous media were performed using tetrabutylammonium bromide, trifluoroacetic acid, and hydrogen peroxide under mild conditions. Oxidative bromination reaction of alkenes was found to afford the corresponding vic-bromides. Furthermore, this oxidative bromination system is applicable to the oxidative bromination of alkynes, arenes, and 3,4-dihydronaphthalen-1(2H)-one. A gram-scale bromination reaction was also performed successfully.
- Moriuchi, Toshiyuki,Fukui, Yasuhiro,Sakuramoto, Takashi,Hirao, Toshikazu
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supporting information
p. 1708 - 1710
(2017/11/23)
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- Cross-Dehydrogenative-Coupling of Alkoxybenzenes with Toluenes: Copper(II) Halide Mediated Tandem Halo/Benzylation of Arenes
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A cross-dehydrogenative-coupling of alkoxybenzenes and toluenes with concomitant halogenation is reported. Conditions employed were the use of stoichiometric copper halide salts and dialkylperoxides to afford a range of bromoalkoxydi- and triarylmethanes. Preliminary mechanistic studies suggest that the in situ production of haloarenes (or dihaloarenes) followed by a copper-mediated coupling of a benzylic radical is operational.
- Storr, Thomas E.,Teskey, Christopher J.,Greaney, Michael F.
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supporting information
p. 18169 - 18178
(2016/12/16)
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- Photocatalytic Selective Bromination of Electron-Rich Aromatic Compounds Using Microporous Organic Polymers with Visible Light
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Pure organic, heterogeneous, metal-free, and visible light-active photocatalysts offer a more sustainable and environmentally friendly alternative to traditional metal-based catalysts. Here we report a series of microporous organic polymers containing photoactive conjugated organic semiconductor units as heterogeneous photocatalysts for a visible-light-promoted, highly selective bromination reaction of electron-rich aromatic compounds using HBr as a bromine source and molecular oxygen as a clean oxidant. Via a simple Friedel-Crafts alkylation reaction, the microporous organic polymers were obtained by cross-linking of organic semiconductor compounds with defined valence and conduction band positions. The utilization of the simply prepared porous polymer-based photocatalytic systems opens new opportunities toward a sustainable and efficient material design for catalysis.
- Li, Run,Wang, Zi Jun,Wang, Lei,Ma, Beatriz Chiyin,Ghasimi, Saman,Lu, Hao,Landfester, Katharina,Zhang, Kai. A. I.
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p. 1113 - 1121
(2016/02/18)
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- Effective bromo and chloro peroxidation catalysed by tungsten(vi) amino triphenolate complexes
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Amino triphenolate tungsten(vi) complexes have been prepared and they proved to be efficient catalysts in haloperoxidation reactions using hydrogen peroxide as a terminal oxidant and inorganic sources of halides. In particular, interesting results have been obtained in the challenging chloroperoxidation reactivity (catalyst loading down to 0.05% with TONs up to 900). A comparison among three different metal complexes bearing the same ligand (vanadium(v), molybdenum(vi) and tungsten(vi)) showed much better performances of the last complex both on bromo and chloro peroxidations.
- Badetti, Elena,Romano, Francesco,Marchiò, Luciano,Ta?kesenlio?lu, Sara,Da?tan, Arif,Zonta, Cristiano,Licini, Giulia
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p. 14603 - 14608
(2016/09/28)
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- Efficient and Practical Oxidative Bromination and Iodination of Arenes and Heteroarenes with DMSO and Hydrogen Halide: A Mild Protocol for Late-Stage Functionalization
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An efficient and practical system for inexpensive bromination and iodination of arenes as well as heteroarenes by using readily available dimethyl sulfoxide (DMSO) and HX (X = Br, I) reagents is reported. This mild oxidative system demonstrates a versatile protocol for the synthesis of aryl halides. HX (X = Br, I) are employed as halogenating reagents when combined with DMSO which participates in the present chemistry as a mild and inexpensive oxidant. This oxidative system is amenable to late-stage bromination of natural products. The kilogram-scale experiment (>95% yield) shows great potential for industrial application.
- Song, Song,Sun, Xiang,Li, Xinwei,Yuan, Yizhi,Jiao, Ning
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supporting information
p. 2886 - 2889
(2015/06/30)
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- Practical and metal-free electrophilic aromatic halogenation by interhalogen compounds generated in situ from N-halosuccinimide and catalytic TMSCL
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Halomonochloride compounds (ClCl, BrCl, ICl) generated in situ from N-halosuccinimide and catalytic chlorotrimethylsilane (TMSCl, 0.1 equiv) can efficiently halogenate aromatic compounds to give halogenated products in good to excellent yields and selectivities. The reaction can be carried out at room temperature or at lower temperatures, requires only one hour, is practical to apply to a wide range of substrates, and provides a simple access to a variety of haloarene compounds. Georg Thieme Verlag Stuttgart New York.
- Maibunkaew, Tapanee,Thongsornkleeb, Charnsak,Tummatorn, Jumreang,Bunrit, Anon,Ruchirawat, Somsak
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supporting information
p. 1769 - 1775
(2014/08/05)
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- Oxidative bromination reaction using vanadium catalyst and aluminum halide under molecular oxygen
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The vanadium-catalyzed oxidative bromination reaction of arenes, alkenes, and alkynes was performed in the presence of AlBr3 to provide an alternative method for conventional bromination using hazardous bromine. The catalytic cycle is formed under molecular oxygen, which is more advantageous to vanadium bromoperoxidase (VBrPO) requiring hydrogen peroxide as a terminal oxidant.
- Kikushima, Kotaro,Moriuchi, Toshiyuki,Hirao, Toshikazu
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supporting information; experimental part
p. 340 - 342
(2010/03/04)
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- Vanadium-catalyzed oxidative bromination promoted by Br?nsted acid or Lewis acid
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The oxidative bromination of arenes was induced by a vanadium catalyst in the presence of a bromide salt and a Br?nsted acid or a Lewis acid under molecular oxygen, which provides an eco-friendly bromination method as compared with a conventional bromination one with bromine. This catalytic reaction could be applied to the bromination of alkenes and alkynes to give the corresponding vic-bromides. Use of aluminum halide as a Lewis acid in place of a Br?nsted acid was demonstrated to provide a more practical protocol for the oxidative bromination. From ketones, α-bromination products were obtained. AlBr3 was found to serve as both a bromide source and a Lewis acid to induce the bromination smoothly. 51V NMR experiment showed that this catalytic bromination is likely to depend on the redox cycle of a vanadium catalyst under molecular oxygen.
- Kikushima, Kotaro,Moriuchi, Toshiyuki,Hirao, Toshikazu
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experimental part
p. 6906 - 6911
(2010/09/18)
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- Regioselective copper-catalyzed chlorination and bromination of arenes with O2 as the oxidant
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Electron-rich aromatic C-H bonds undergo regioselective chlorination and bromination in the presence of CuX2, LiX (X = Cl, Br) and molecular oxygen. Preliminary mechanistic insights suggest that the bromination and chlorination reactions proceed by different pathways.
- Yang, Lujuan,Lu, Zhan,Stahl, Shannon S.
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supporting information; experimental part
p. 6460 - 6462
(2010/03/04)
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- A xerogel-sequestered selenoxide catalyst for brominations with hydrogen peroxide and sodium bromide in an aqueous environment
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(Chemical Equation Presented) 4-(Hydroxymethyl)phenyl benzyl selenoxide (4) sequestered in a halide-permeable, Class II xerogel formed from 10/90 (mol/mol) 3-aminopropyltriethoxysilane/tetraethoxysilane catalyzes the bromination of organic substrates (4-pentenoic acid, 3,5-dihydroxybenzoic acid, 1,3,5-trimethoxybenzene, N-phenylmorpholine, and N,N-dimethylaniline) with NaBr and H2O2. Catalyst performance (reaction rate) when sequestered within the halide-permeable xerogel is 23-fold greater in comparison to xerogel-free catalyst in solution. The catalyst is easily separated from the reaction mixture via filtration and the recovered catalyst can be reused without loss of activity through formation of the first 80 mol of product per mole of catalyst.
- Bennett, Stephanie M.,Tang, Ying,McMaster, Danielle,Bright, Frank V.,Detty, Michael R.
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p. 6849 - 6852
(2008/12/22)
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- An efficient vanadium-catalyzed bromination reaction
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An efficient catalytic oxidative bromination of arenes, alkenes, and alkynes in aqueous media was achieved under relatively mild conditions by using NH4VO3 catalyst combined with H2O2, HBr, and KBr. Dodecyltrimethylammonium bromide was found to serve as an efficient surfactant to facilitate the NH4VO3-catalyzed bromination in aqueous media.
- Moriuchi, Toshiyuki,Yamaguchi, Mitsuaki,Kikushima, Kotaro,Hirao, Toshikazu
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p. 2667 - 2670
(2008/02/03)
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- Pyridinium hydrobromide perbromide induces ipsobromodeformylation in o-hydroxy and o-methoxy substituted aromatic aldehydes
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The reaction of o-hydroxy and o-methoxy substituted aromatic aldehydes with PHPB in pyridine gives aromatic bromination products including those arising from ipsobromodeformylation.
- Córdoba, Rubén,Plumet, Joaquín
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p. 9303 - 9305
(2007/10/03)
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- Synthesis of brominated compounds. A convenient molybdenum-catalyzed procedure inspired by the mode of action of haloperoxidases
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A two-phase (CHCl3/H2O) procedure for the synthesis of halogenated compounds has recently been developed. Such procedure mimics the mode of action of the enzymes haloperoxidases which contain vanadium in their active center. We have investigated the possibility to substitute vanadium with molybdenum. The molybdenum-based reactions show some advantages over the vanadium-based ones. In fact reaction times are shorter and overall yields are larger, under similar experimental conditions, both in the reaction with double bonds as well as with aromatic rings. Moreover, with double bonds, the molybdenum catalyzed process preferentially yields bromohydrins which are valuable synthetic intermediates. On the other hand, the molybdenum-catalyzed reactions show peculiar mechanistic features which deserve further investigation.
- Conte, Valeria,Di Furia, Fulvio,Moro, Stefano
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p. 8609 - 8612
(2007/10/03)
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- Catalytic Halogenation of Selected Organic Compounds Mimicking Vanadate-dependent Marine Metalloenzymes
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The ammonium metavanadate, mimicking vanadate-dependent metalloenzymes, efficiently catalyses the halogenation of a variety of organic substrates in dilute conditions in moderate to good yields using dilute hydrogen peroxide (30percent) as an oxidizing agent exhibiting remarkable ortho selectivity with electron-rich aromatics.
- Dinesh, Chimmanamada U.,Kumar, Rajiv,Pandey, Bipin,Kumar, Pradeep
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p. 611 - 612
(2007/10/02)
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- Bromophloroglucinols and their methyl ethers
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All 16 bromination products of phloroglucinol and its methyl ethers, as well as five bromoresorcinols and three of their dimethyl ethers, were synthesized and analyzed by nuclear magnetic resonance spectroscopy.Two or three equivalents of bromine convert phloroglucinol to di- and tribromophloroglucinol, 5-methoxyresorcinol to the tri- and 2,4-dibromo, 3,5-dimethoxyphenol to the tri- and 2,6-dibromo, and 1,3,5-trimethoxybenzene to the dibromo compound.With one equivalent of bromine, 3,5-dimethoxyphenol reacts preferentially at C-2 while 5-methoxyresorcinol gives both monobromo isomers.Partial debromination with sodium sulfite yields successively 2,4-dibromo- and 2-bromo-5-methoxyresorcinol from the tribromo compound but fails with brominated 3,5-dimethoxyphenol.In the resorcinol series, C-2 is invariably the least reactive position. 4,6-Dibromo-5-methoxyresorcinol and 2,4-dibromo-3,5-dimethoxyphenol are accessible by methylation of dibromophloroglucinol, obtained from 3,5-dibromo-2,4,6-trihydroxybenzoic acid by decarboxylation.In contrast to resorcinol and tribromoresorcinol, the partial bromination of pholoroglucinol and debromination of tribromopholoroglucinol are not selective.The 13Cnmr spectra of bromophloroglucinol methyl ethers show characteristic downfield shifts for methoxy groups orthogonal to the aromatic ring plane.
- Kiehlmann, E.,Lauener, R. W.
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p. 335 - 344
(2007/10/02)
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- Dilithiation of Aromatic Ethers
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The lithiations of anisole and all the isomeric dimethoxy- and trimethoxybenzenes with 2-5 equiv of n-butyllithium/TMEDA complex have been investigated under a variety of reaction conditions.Anisole and m-dimethoxybenzene do not undergo dilithiatian, but
- Crowther, G. P.,Sundberg, Richard J.,Sarpeshkar, Ashok M.
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p. 4657 - 4663
(2007/10/02)
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