- Activation of Aryl Carboxylic Acids by Diboron Reagents towards Nickel-Catalyzed Direct Decarbonylative Borylation
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The Ni-catalyzed decarbonylative borylation of (hetero)aryl carboxylic acids with B2cat2 has been achieved without recourse to any additives. This Ni-catalyzed method exhibits a broad substrate scope covering poorly reactive non-ortho-substituted (hetero)aryl carboxylic acids, and tolerates diverse functional groups including some of the groups active to Ni0 catalysts. The key to achieve this decarbonylative borylation reaction is the choice of B2cat2 as a coupling partner that not only acts as a borylating reagent, but also chemoselectively activates aryl carboxylic acids towards oxidative addition of their C(acyl)?O bond to Ni0 catalyst via the formation of acyloxyboron compounds. A combination of experimental and computational studies reveals a detailed plausible mechanism for this reaction system, which involves a hitherto unknown concerted decarbonylation and reductive elimination step that generates the aryl boronic ester product. This mode of boron-promoted carboxylic acid activation is also applicable to other types of reactions.
- Deng, Xi,Guo, Jiandong,Su, Weiping,Wang, Xiaotai,Zhang, Xiaofeng
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supporting information
p. 24510 - 24518
(2021/08/12)
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- Isodesmic C-H Borylation: Perspectives and Proof of Concept of Transfer Borylation Catalysis
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The potential advantages of using arylboronic esters as boron sources in C-H borylation are discussed. The concept is showcased using commercially available 2-mercaptopyridine as a metal-free catalyst for the transfer borylation of heteroarenes using arylboronates as borylation agents. The catalysis shows a unique functional group tolerance among C-H borylation reactions, tolerating notably terminal alkene and alkyne functional groups. The mechanistic investigation is also described.
- Rochette, étienne,Desrosiers, Vincent,Soltani, Yashar,Fontaine, Frédéric-Georges
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supporting information
p. 12305 - 12311
(2019/08/20)
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- Metal-Free Radical Borylation of Alkyl and Aryl Iodides
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A metal-free radical borylation of alkyl and aryl iodides with bis(catecholato)diboron (B2cat2) as the boron source under mild conditions is introduced. The borylation reaction is operationally easy to conduct and shows high functional group tolerance and broad substrate scope. Radical clock experiments and density functional theory calculations provide insights into the mechanism and rate constants for C-radical borylation with B2cat2 are disclosed.
- Cheng, Ying,Mück-Lichtenfeld, Christian,Studer, Armido
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p. 16832 - 16836
(2018/11/23)
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- Solid-state 11B and 13C NMR, IR, and X-ray crystallographic characterization of selected arylboronic acids and their catechol cyclic esters
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Nine arylboronic acids, seven arylboronic catechol cyclic esters, and two trimeric arylboronic anhydrides (boroxines) are investigated using 11B solid-state NMR spectroscopy at three different magnetic field strengths (9.4, 11.7, and 21.1T). Through the analysis of spectra of static and magic-angle spinning samples, the 11B electric field gradient and chemical shift tensors are determined. The effects of relaxation anisotropy and nutation field strength on the 11B NMR line shapes are investigated. Infrared spectroscopy was also used to help identify peaks in the NMR spectra as being due to the anhydride form in some of the arylboronic acid samples. Seven new X-ray crystallographic structures are reported. Calculations of the 11B NMR parameters are performed using cluster model and periodic gauge-including projector-augmented wave (GIPAW) density functional theory (DFT) approaches, and the results are compared with the experimental values. Carbon-13 solid-state NMR experiments and spectral simulations are applied to determine the chemical shifts of the ipso carbons of the samples. One bond indirect 13C-11B spin-spin (J) coupling constants are also measured experimentally and compared with calculated values. The 11B/10B isotope effect on the 13C chemical shift of the ipso carbons of arylboronic acids and their catechol esters, as well as residual dipolar coupling, is discussed. Overall, this combined X-ray, NMR, IR, and computational study provides valuable new insights into the relationship between NMR parameters and the structure of boronic acids and esters. Copyright
- Oh, Se-Woung,Weiss, Joseph W. E.,Kerneghan, Phillip A.,Korobkov, Ilia,Maly, Kenneth E.,Bryce, David L.
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experimental part
p. 388 - 401
(2012/08/13)
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- Chelate restrained boron cations for intermolecular electrophilic arene borylation
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Highly electrophilic boron species that borylate arenes are generated by halide abstraction from CatBX (Cat = catecholato, C6H 4O22-, X = Cl or Br) by [Et3Si] [CbBr6] (CbBr6 = [closo-1-H-CB11H 5Br6]-). A transient [CatB][CbBr6] related species reacts as a synthetic equivalent of [CatB]+ in intermolecular electrophilic borylation, with reactions proceeding rapidly at 25 °C. The [CatB]+ moiety was shown to be strongly Lewis acidic on the basis of 1H and 31P{1H} NMR spectroscopy of the crotonaldehyde and triethylphosphine oxide adducts, respectively. Catalytic quantities of [Et3Si][CbBr6] and CatBX were effective for the high-yielding borylation of arenes by CatBH in a highly atom efficient cycle with H2 the only byproduct. Successful catalysis was dependent on the robust [CbBr6]- anion and the use of electrophile-resistant borane sources
- Del Grosso, Alessandro,Pritchard, Robin G.,Muryn, Chris A.,Ingleson, Michael J.
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p. 241 - 249
(2010/04/04)
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- Guest-encapsulation properties of a self-assembled capsule by dynamic boronic ester bonds
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Two molecules of tetrakis(dihydroxyboryl)-cavitand 1a as an aromatic cavity and four molecules of 1,2-bis(3,4-dihydroxyphenyl)ethane 2 as an equatorial linker self-assemble into capsule 3a via the formation of eight dynamic boronic ester bonds in CDClsub
- Nishimura, Naoki,Yoza, Kenji,Kobayashi, Kenji
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p. 777 - 790
(2010/04/01)
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- Synthesis and reactivity of cobalt boryl complexes
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The synthesis and reactivity of phosphine-cobalt boryls, were investigated. The reactivity studies have shown that alkyne diboration takes place and borylation of aryl bromides is possible with low selectivity. Boryl transfer was investigated initially by
- Adams, Christopher J.,Baber, R. Angharad,Batsanov, Andrei S.,Bramham, George,Charmant, Jonathan P.H.,Haddow, Mairi F.,Howard, Judith A.K.,Lam, Wai Han,Lin, Zhenyang,Marder, Todd B.,Norman, Nicholas C.,Orpen, A. Guy
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p. 1370 - 1373
(2007/10/03)
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- C-H Activation and Functionalization of Unsaturated Hydrocarbons by Transition-Metal Boryl Complexes
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Transition-metal boryl complexes of the form Cp′Fe(CO)LBcat and (CO)5MBcat, where Cp′ = C5H5, C5Me5, M = Mn, Re, L = CO, PMe3, and cat = 1,2-O2C6H4, were synthesized by reaction of ClBcat with [Cp′Fe(CO)L]- or [M(CO)5]-. X-ray crystal structures of CpFe-(CO)2Bcat, Cp*Fe(CO)2Bcat, and (CO)5MnBcat were obtained. Upon irradiation, these metal boryl complexes reacted with arenes and alkenes to form aryl- and vinylboronate ester products in moderate to high yields. Monosubstituted arenes with methyl, chloro, trifluoromethyl, methoxy, and dimethylamino substituents were used as substrates, and the resulting ratios of ortho- to meta- to para-substituted arene products were measured. No significant electronic effects were observed, indicating that the chemistry is not occurring through a typical electrophilic aromatic substitution pathway. Competition experiments between toluene and other substituted arenes were conducted. Reactivity differences were small, but anisole was found to have the fastest rate of reaction. Kinetic isotope effects were measured for the reaction of CpFe(CO)2Bcat, (CO)5MnBcat, or (CO)5ReBcat with benzene/ benzene-d6 mixtures and were found to be 3.3 ± 0.4, 2.1 ± 0.1, and 5.4 ± 0.4, respectively. This difference in isotope effect along with differences in selectivities with substituted arsenic reagents rules out a mechanism by which a common free Beat radical attacks free substrate. Several experiments were also conducted to probe for CO loss. A 13CO-labeling experiment, CO inhibition experiment, and PMe3 trapping experiment indicate that the mechanism most likely proceeds through irreversible CO loss to form a 16-electron intermediate. Functionalization of alkenes to form vinylboronate esters was also observed, and mechanistic studies showed the absence of a measurable kinetic isotope effect for reaction of CpFe(CO)2Bcat or (CO)5ReBcat with ethylene/ethylene-d4 mixtures or for reaction with ethylene-d2.
- Waltz, Karen M.,Muhoro, Clare N.,Hartwig, John F.
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p. 3383 - 3393
(2008/10/08)
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- Derivatization and Mass Spectrometric Investigation of Substituted Benzeneboronic Acids. The Use of Linked Scanning During Gas Chromatography Mass Spectrometry
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Substituted benzeneboronic acids are important intermediates in the synthesis of support matrices for affinity chromatography but their analysis by mass spectrometry is hindered by thermal reactions in the ion source.A simple derivatization with 1,2- or 1
- Longstaff, Colin,Rose, Malcolm Edward
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p. 508 - 518
(2007/10/02)
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