- Remarkably Efficient Iridium Catalysts for Directed C(sp2)-H and C(sp3)-H Borylation of Diverse Classes of Substrates
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Here we describe the discovery of a new class of C-H borylation catalysts and their use for regioselective C-H borylation of aromatic, heteroaromatic, and aliphatic systems. The new catalysts have Ir-C(thienyl) or Ir-C(furyl) anionic ligands instead of the diamine-type neutral chelating ligands used in the standard C-H borylation conditions. It is reported that the employment of these newly discovered catalysts show excellent reactivity and ortho-selectivity for diverse classes of aromatic substrates with high isolated yields. Moreover, the catalysts proved to be efficient for a wide number of aliphatic substrates for selective C(sp3)-H bond borylations. Heterocyclic molecules are selectively borylated using the inherently elevated reactivity of the C-H bonds. A number of late-stage C-H functionalization have been described using the same catalysts. Furthermore, we show that one of the catalysts could be used even in open air for the C(sp2)-H and C(sp3)-H borylations enabling the method more general. Preliminary mechanistic studies suggest that the active catalytic intermediate is the Ir(bis)boryl complex, and the attached ligand acts as bidentate ligand. Collectively, this study underlines the discovery of new class of C-H borylation catalysts that should find wide application in the context of C-H functionalization chemistry.
- Chattopadhyay, Buddhadeb,Hassan, Mirja Md Mahamudul,Hoque, Md Emdadul
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supporting information
p. 5022 - 5037
(2021/05/04)
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- Cross-Coupling through Ag(I)/Ag(III) Redox Manifold
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In ample variety of transformations, the presence of silver as an additive or co-catalyst is believed to be innocuous for the efficiency of the operating metal catalyst. Even though Ag additives are required often as coupling partners, oxidants or halide scavengers, its role as a catalytically competent species is widely neglected in cross-coupling reactions. Most likely, this is due to the erroneously assumed incapacity of Ag to undergo 2e? redox steps. Definite proof is herein provided for the required elementary steps to accomplish the oxidative trifluoromethylation of arenes through AgI/AgIII redox catalysis (i. e. CEL coupling), namely: i) easy AgI/AgIII 2e? oxidation mediated by air; ii) bpy/phen ligation to AgIII; iii) boron-to-AgIII aryl transfer; and iv) ulterior reductive elimination of benzotrifluorides from an [aryl-AgIII-CF3] fragment. More precisely, an ultimate entry and full characterization of organosilver(III) compounds [K]+[AgIII(CF3)4]? (K-1), [(bpy)AgIII(CF3)3] (2) and [(phen)AgIII(CF3)3] (3), is described. The utility of 3 in cross-coupling has been showcased unambiguously, and a large variety of arylboron compounds was trifluoromethylated via [AgIII(aryl)(CF3)3]? intermediates. This work breaks with old stereotypes and misconceptions regarding the inability of Ag to undergo cross-coupling by itself.
- Demonti, Luca,Mézailles, Nicolas,Nebra, Noel,Saffon-Merceron, Nathalie
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supporting information
p. 15396 - 15405
(2021/10/12)
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- Transformations of Aryl Ketones via Ligand-Promoted C?C Bond Activation
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The coupling of aromatic electrophiles (aryl halides, aryl ethers, aryl acids, aryl nitriles etc.) with nucleophiles is a core methodology for the synthesis of aryl compounds. Transformations of aryl ketones in an analogous manner via carbon–carbon bond activation could greatly expand the toolbox for the synthesis of aryl compounds due to the abundance of aryl ketones. An exploratory study of this approach is typically based on carbon–carbon cleavage triggered by ring-strain release and chelation assistance, and the products are also limited to a specific structural motif. Here we report a ligand-promoted β-carbon elimination strategy to activate the carbon–carbon bonds, which results in a range of transformations of aryl ketones, leading to useful aryl borates, and also to biaryls, aryl nitriles, and aryl alkenes. The use of a pyridine-oxazoline ligand is crucial for this catalytic transformation. A gram-scale borylation reaction of an aryl ketone via a simple one-pot operation is reported. The potential utility of this strategy is also demonstrated by the late-stage diversification of drug molecules probenecid, adapalene, and desoxyestrone, the fragrance tonalid as well as the natural product apocynin.
- Dai, Hui-Xiong,Li, Hanyuan,Li, Ling-Jun,Liu, Qi-Sheng,Ma, Biao,Wang, Mei-Ling,Wang, Xing,Wang, Zhen-Yu,Xu, Hui
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supporting information
p. 14388 - 14393
(2020/07/06)
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- Iron-catalysed C(sp2)-H borylation enabled by carboxylate activation
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Arene C(sp2)-H bond borylation reactions provide rapid and efficient routes to synthetically versatile boronic esters. While iridium catalysts are well established for this reaction, the discovery and development of methods using Earth-abundant alternatives is limited to just a few examples. Applying an in situ catalyst activation method using air-stable and easily handed reagents, the iron-catalysed C(sp2)-H borylation reactions of furans and thiophenes under blue light irradiation have been developed. Key reaction intermediates have been prepared and characterised, and suggest two mechanistic pathways are in action involving both C-H metallation and the formation of an iron boryl species.
- Britton, Luke,Docherty, Jamie H.,Dominey, Andrew P.,Thomas, Stephen P.
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supporting information
(2020/02/22)
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- Iridium-Catalyzed Silylation of Five-Membered Heteroarenes: High Sterically Derived Selectivity from a Pyridyl-Imidazoline Ligand
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The steric effects of substituents on five-membered rings are less pronounced than those on six-membered rings because of the difference in bond angles. Thus, the regioselectivities of reactions of five-membered heteroarenes that occur with selectivities dictated by steric effects, such as the borylation of C?H bonds, have been poor in many cases. We report that the silylation of five-membered-ring heteroarenes occurs with high sterically derived regioselectivity when catalyzed by the combination of [Ir(cod)(OMe)]2 (cod=1,5-cyclooctadiene) and a phenanthroline ligand or a new pyridyl-imidazoline ligand that further increases the regioselectivity. The silylation reactions with these catalysts produce high yields of heteroarylsilanes from functionalization at the most sterically accessible C?H bonds of these rings under conditions that the borylation of C?H bonds with previously reported catalysts formed mixtures of products or products that are unstable. The heteroarylsilane products undergo cross-coupling reactions and substitution reactions with ipso selectivity to generate heteroarenes that bear halogen, aryl, and perfluoroalkyl substituents.
- Hartwig, John F.,Karmel, Caleb,Kharitonova, Elena V.,Rubel, Camille Z.
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supporting information
p. 6074 - 6081
(2020/02/25)
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- Pd II -Porphyrin Complexes - The First Use as Safer and Efficient Catalysts for Miyaura Borylation
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We have developed a simple and convenient procedure for the preparation of pinacol arylboronates from aryl/heteroaryl bromides and bis(pinacolato)diborane using a Pd II -porphyrin complex as a catalyst. Seven different Pd II -porphyrin complexes (Pd II -T m HPP, Pd II -T m CPP, Pd II -TPP, Pd II -TST p SPP, Pd II -T p CPP, Pd II -T p TP, and Pd II -T p AP) have been synthesized and investigated for their catalytic influence in the Miyaura borylation.
- Rao, Kanusu Umamaheswara,Venkateswarlu, Katta
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supporting information
p. 1055 - 1060
(2018/03/23)
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- Preparation method of aryl borate ester and allyl borate ester
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The invention discloses a preparation method of aryl borate ester and allyl borate ester. The method comprises the following step: under the catalytic action of pyridine or a derivative thereof, carrying out 1) or 2) to obtain substituted boric acid ester shown as a formula I-1 or a formula I-2: 1) a reaction of a halide, bi-boric acid ester and alkoxide; 2) a reaction of a halide and a bi-boric acid ester-alkoxide complex. The method is an efficient preparation method of the aryl borate ester and the allyl borate ester. In the preparation method provided by the invention, the inexpensive pyridine or the derivative thereof is taken as a catalyst instead of a transition metal catalyst, the reaction conditions are mild, the reaction yield is high, residues of trace transition metal in a boronation product are avoided, and the cost of an aryl and allyl borate ester synthesis reaction is lowered.
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Paragraph 0072-0075; 0078
(2017/07/12)
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- Pyridine-catalyzed radical borylation of aryl halides
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A pyridine-catalyzed transition-metal-free borylation reaction of haloarenes has been developed based on the selective cross-coupling of an aryl radical and a pyridine-stabilized boryl radical. Arylboronates were produced from haloarenes under mild conditions. This borylation reaction features a broad substrate scope, operational simplicity, and gram-scale synthetic ability.
- Zhang, Li,Jiao, Lei
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supporting information
p. 607 - 610
(2017/05/15)
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- Development of a concise synthesis of ouabagenin and hydroxylated corticosteroid analogues
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The natural product ouabagenin is a complex cardiotonic steroid with a highly oxygenated skeleton. This full account describes the development of a concise synthesis of ouabagenin, including the evolution of synthetic strategy to access hydroxylation at the C19 position of a steroid skeleton. In addition, approaches to install the requisite butenolide moiety at the C17 position are discussed. Lastly, methodology developed in this synthesis has been applied in the generation of novel analogues of corticosteroid drugs bearing a hydroxyl group at the C19 position.(Chemical Equation Presented).
- Renata, Hans,Zhou, Qianghui,Dünstl, Georg,Felding, Jakob,Merchant, Rohan R.,Yeh, Chien-Hung,Baran, Phil S.
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supporting information
p. 1330 - 1340
(2015/02/19)
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- Efficient synthesis of aryl boronates via zinc-catalyzed cross-coupling of alkoxy diboron reagents with aryl halides at room temperature
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A zinc(II)/NHC system catalyzes the borylation of aryl halides with diboron (4) reagents in the presence of KOMe at rt. This transformation can be applied to a broad range of substrates with high functional group compatibility. Radical scavenger experiments do not support a radical-mediated process.
- Bose, Shubhankar Kumar,Marder, Todd B.
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supporting information
p. 4562 - 4565
(2015/01/08)
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- PROCESS FOR PRODUCTION OF HETEROARYL-TYPE BORON COMPOUNDS WITH IRIDIUM CATALYST
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The present invention provides an economically and industrially superior simple process that enables the selective production of an aromatic heterocyclic monoboron compound and aromatic heterocyclic diboron compound at a satisfactory yield and in a desired ratio by reacting an aromatic heterocyclic compound and a boron compound in a single step under mild conditions while changing only the charged ratios of the raw materials. The present invention provides a production process of a heteroaryl mono- or diboron compound comprising an aromatic heterocyclic compound and a boron compound in the form of bis(pinacolate)diboron or pinacolate diborane in the presence of a iridium-containing catalyst and a ligand such as a bipyridyl ligand.
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- Iridium-catalyzed C-H coupling reaction of heteroaromatic compounds with bis(pinacolato)diboron: Regioselective synthesis of heteroarylboronates
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The C-H coupling of aromatic heterocycles with bis(pinacolato)diboron was carried out in octane at 80-100°C in the presence of a 1/2[IrCl(COD)]2-(4,4′-di-tert-butyl-2,2′-bipyridine) catalyst (3 mol%). The reactions of five-membered substrates such as thiophene, furan, pyrrole, and their benzo-fused derivatives exclusively produced 2-borylated products, whereas those of six-membered heterocycles including pyridine and quinoline selectively occurred at the 3-position. Regioselective synthesis of bis(boryl)heteroaromatics was also achieved by using an almost equimolar amount of substrates and the diboron.
- Takagi, Jun,Sato, Kazuaki,Hartwig, John F,Ishiyama, Tatsuo,Miyaura, Norio
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p. 5649 - 5651
(2007/10/03)
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- Certain heteroaryl substituted thiol inhibitors of endothelin-converting enzyme
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Novel thiol derivatives of formula I or of the formula Ia wherein the variables have the meanings as defined hereinbefore.
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