- First preparation of a novel polyol resin for purifying arylboronic acids
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A novel polystyrene-supported triol resin was first prepared by reaction of the Merrifield resin with trometamol. Using this resin, arylboronic acids were efficiently isolated and purified through a capture-release procedure in organic solvents. However, in basic aqueous solvents arylboronic acids were immobilized on the resin only with low yield.
- Liu, Fu Long,Wan, Sheng Biao,Jiang, Tao
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Read Online
- A novel redox-sensitive protecting group for boronic acids, MPMP-diol
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A new boronic acid protecting group, 1-(4-methoxyphenyl)-2-methylpropane-1, 2-diol (MPMP-diol), has been developed. Both protection and deprotection can be accomplished under mild conditions with quantitative conversions. The deprotection can be carried out using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).
- Yan, Jun,Jin, Shan,Wang, Binghe
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- N-Nitroheterocycles: Bench-Stable Organic Reagents for Catalytic Ipso-Nitration of Aryl- And Heteroarylboronic Acids
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Photocatalytic and metal-free protocols to access various aromatic and heteroaromatic nitro compounds through ipso-nitration of readily available boronic acid derivatives were developed using non-metal-based, bench-stable, and recyclable nitrating reagents. These methods are operationally simple, mild, regioselective, and possess excellent functional group compatibility, delivering desired products in up to 99% yield.
- Budinská, Alena,Katayev, Dmitry,Passera, Alessandro,Zhang, Kun
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supporting information
(2020/03/30)
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- An easy route to (hetero)arylboronic acids
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An unprecedented spontaneous reactivity between diazonium salts and diboronic acid has been unveiled, leading to a versatile arylboronic acid synthesis directly from (hetero)arylamines. This fast reaction (35 min overall) tolerates a wide range of functional groups and is carried out under very mild conditions. The radical nature of the reaction mechanism has been investigated.
- Erb, William,Hellal, Akila,Albini, Mathieu,Rouden, Jacques,Blanchet, Jerome
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p. 6608 - 6612
(2014/06/09)
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- Organotrifluoroborate hydrolysis: Boronic acid release mechanism and an acid-base paradox in cross-coupling
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The hydrolysis of potassium organotrifluoroborate (RBF3K) reagents to the corresponding boronic acids (RB(OH)2) has been studied in the context of their application in Suzuki-Miyaura coupling. The "slow release" strategy in such SM couplings is only viable if there is an appropriate gearing of the hydrolysis rate of the RBF3K reagent with the rate of catalytic turnover. In such cases, the boronic acid RB(OH)2 does not substantially accumulate, thereby minimizing side reactions such as oxidative homocoupling and protodeboronation. The study reveals that the hydrolysis rates (THF, H2O, Cs2CO 3, 55 °C) depend on a number of variables, resulting in complex solvolytic profiles with some RBF3K reagents. For example, those based on p-F-phenyl, naphthyl, furyl, and benzyl moieties are found to require acid catalysis for efficient hydrolysis. This acid-base paradox assures their slow hydrolysis under basic Suzuki-Miyaura coupling conditions. However, partial phase-splitting of the THF/H2O induced by the Cs2CO 3, resulting in a lower pH in the bulk medium, causes the reaction vessel shape, material, size, and stirring rate to have a profound impact on the hydrolysis profile. In contrast, reagents bearing, for example, isopropyl, β-styryl, and anisyl moieties undergo efficient "direct" hydrolysis, resulting in fast release of the boronic acid while reagents bearing, for example, alkynyl or nitrophenyl moieties, hydrolyze extremely slowly. Analysis of B-F bond lengths (DFT) in the intermediate difluoroborane, or the Swain-Lupton resonance parameter (R) of the R group in RBF3K, allows an a priori evaluation of whether an RBF3K reagent will likely engender "fast", "slow", or "very slow" hydrolysis. An exception to this correlation was found with vinyl-BF 3K, this reagent being sufficiently hydrophilic to partition substantially into the predominantly aqueous minor biphase, where it is rapidly hydrolyzed.
- Lennox, Alastair J. J.,Lloyd-Jones, Guy C.
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supporting information; experimental part
p. 7431 - 7441
(2012/06/16)
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- Efficient hydrolysis of organotrifluoroborates via silica gel and water
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(Chemical Equation Presented) A general, mild, and efficient method for the hydrolysis of organotrifluoroborates to unveil boronic acids using silica gel and H2O was developed. This method proved to be tolerant of a broad range of aryl-, heteroaryl-, alkenyl-, and alkyltrifluoroborates as well as structurally diverse aminomethylated organotrifluoroborates.As anticipated, electron-rich substrates provided the corresponding boronic acids more readily than electron-poor substrates, owing to the resonance-stabilized difluoroborane intermediate. The method developed was expanded further for the conversion of organotrifluoroborates to the corresponding boronate esters. 2009 American Chemical Society.
- Molander, Gary A.,Cavalcanti, Livia N.,Canturk, Belgin,Pan, Po-Shen,Kennedy, Lauren E.
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supporting information; experimental part
p. 7364 - 7369
(2010/01/16)
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- Substituent effects on aryltrifluoroborate solvolysis in water: Implications for Suzuki-Miyaura coupling and the design of stable 18F-labeled aryltrifluoroborates for use in PET imaging
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(Chemical Equation Presented) Whereas electron withdrawing substituents retard the rate of aryltrifluoroborate solvolysis, electron-donating groups enhance it. Herein is presented a Hammett analysis of the solvolytic lability of aryltrifluoroborates where log(Ksolv) values correlate to a values with a ρ value of approximately -1. This work provides a predictable rubric for tuning the reactivity of boron for several uses including 18F-labeled PET reagents and has mechanistic implications for ArBF3-enhanced ligandless metal-mediated cross coupling reactions with aryltrifluoroborates.
- Ting, Richard,Harwig, Curtis W.,Lo, Justin,Li, Ying,Adam, Michael J.,Ruth, Thomas J.,Petrin, David M.
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p. 4662 - 4670
(2008/09/20)
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- Benzoxepin-derived estrogen receptor modulators: A novel molecular scaffold for the estrogen receptor
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We present and examine the efficacy of a novel benzoxepin-based scaffold for modulation of the human estrogen receptor. Receptor tolerance of this new molecular scaffold is examined through presentation of experimentally determined antiproliferative effects on human MCF-7 breast tumor cells and measured binding affinities. The effect of functional group substitution on the benzoxepin scaffold is explored through a brief computational structure - activity relationship investigation with molecular simulation.
- Lloyd, David G.,Hughes, Rosario B.,Zisterer, Daniela M.,Williams, D. Clive,Fattorusso, Caterina,Catalanotti, Bruno,Campiani, Giuseppe,Meegan, Mary J.
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p. 5612 - 5615
(2007/10/03)
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- Deprotection of pinacolyl boronate esters by transesterification with polystyrene-boronic acid
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A mild, efficient method for the deprotection of pinacolyl organoboronate esters is described. Treatment of the organoboronate ester with excess polystyrene-boronic acid followed by filtration and evaporation of the solvent provides the corresponding organoboronic acid. Mild deprotection of pinacolyl boronate esters to the corresponding boronic acids was achieved in the presence of excess polystyrene-boronic acid via a transesterification process. The procedure allows for the cleavage of pinacolyl boronate esters in the presence of sensitive functional groups. Crown Copyright
- Pennington, Thomas E.,Kardiman, Cynantya,Hutton, Craig A.
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p. 6657 - 6660
(2007/10/03)
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- Thrombopoietin mimetics
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Invented are non-peptide TPO mimetics. Also invented is a method of treating thrombocytopenia, in a mammal, including a human, in need thereof which comprises administering to such mammal an effective amount of a selected substituted naphthimidazole derivative.
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- An improved protocol for the preparation of 3-pyridyl- and some arylboronic acids
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3-Pyridylboronic acid was prepared in high yield and bulk quantity from 3-bromopyridine via a protocol of lithium-halogen exchange and "in situ quench". This technique was further studied and evaluated on other aryl halides in the preparation of arylboronic acids.
- Li, Wenjie,Nelson, Dorian P.,Jensen, Mark S.,Hoerrner, R. Scott,Cai, Dongwei,Larsen, Robert D.,Reider, Paul J.
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p. 5394 - 5397
(2007/10/03)
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- Cupric acetate mediated N-arylation by arylboronic acids: A preliminary investigation into the scope of application
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A range of NH substrates of varying nucleophilicity were reacted with a selection of electronically diverse aryl boronic acids in the presence of cupric acetate in order to evaluate the generality of a previously described N-arylation procedure. The results of that investigation are discussed.
- Cundy, Darren J.,Forsyth, Stewart A.
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p. 7979 - 7982
(2007/10/03)
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- Reaction of Arylboronic Acids and their Derivatives with Lead Tetra-acetate. The Generation of Aryl-lead Triacetates, and meta- and para-Phenylenebis(lead triacetate), in situ for Electrophilic Arylation
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Arylboronic acids and some of their derivatives have been found to undergo a rapid boron-lead exchange with lead tetra-acetate.In the presence of a catalytic amount of mercury(II) acetate, the reaction produces mainly the aryl-lead triacetate, and it has been developed as a convenient method for in situ generation of these useful electrophilic C-arylating reagents.The reaction allows the generation for the first time of meta- and para-phenylenebis(lead triacetate), compounds which behave as meta- and para-phenylene dication equivalents.
- Morgan, Jacqueline,Pinhey, John T.
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p. 715 - 720
(2007/10/02)
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