- Copper-catalyzed fluorination of 2-pyridyl aryl bromides
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Copper(i)-catalyzed cross-coupling of aryl halides is the subject of extensive interest in synthetic chemistry, but the related catalytic fluorination is unsuccessful. Herein, we have developed a novel copper-catalyzed fluorination of aryl bromides using AgF as the fluorine source. In this transformation a pyridyl directing group is essential for successful catalytic fluorination. A XANES/EXAFS study indicated that the presence of the pyridyl group is essential to stabilize the Cu(i) species and accelerate oxidative addition of the aryl bromide. Further mechanistic studies implicated a Cu(i/iii) catalytic cycle in this Cu(i)-catalyzed fluorination, and final aryl C-F bond formation possibly proceeds through an irreversible reductive elimination of the ArCu(iii)-F species. This rare report of catalytic fluorination by a copper catalyst provides a valuable foundation for further development of Cu(i)-catalyzed fluorination of aryl halides.
- Mu, Xin,Zhang, Hao,Chen, Pinhong,Liu, Guosheng
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- Directing Group-Promoted Inert C?O Bond Activation Using Versatile Boronic Acid as a Coupling Agent
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A simple Ni(cod)2 and carbene mediated strategy facilitates the efficient catalytic cross-coupling of methoxyarenes with a variety of organoboron reagents. Directing groups facilitate the activation of inert C?O bonds in under-utilized aryl methyl ethers enabling their adaptation for C?C cross-coupling reactions as less toxic surrogates to the ubiquitous haloarenes. The method reported enables C?C cross-coupling with readily available and economical arylboronic acid reagents, which is unprecedented, and compares well with other organoboron reagents with similarly high reactivity. Extension to directing group assisted chemo-selective C?O bond cleavage, and further application towards the synthesis of novel bifunctionalized biaryls is reported. Key to the success of this protocol is the use of directing groups proximal to the reaction center to facilitate the activation of the inert C?OMe bond.
- Ambre, Ram,Wang, Ting-Hsuan,Xian, Anmei,Chen, Yu-Shiuan,Liang, Yu-Fu,Jurca, Titel,Zhao, Lili,Ong, Tiow-Gan
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supporting information
p. 17021 - 17026
(2020/11/30)
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- Synthesis of Chemically and Configurationally Stable Monofluoro Acylboronates: Effect of Ligand Structure on their Formation, Properties, and Reactivities
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The recent disclosures of two classes of acylborons, potassium acyltrifluoroborates (KATs) and N-methyliminodiacetyl (MIDA) acylboronates, demonstrated that certain acylboron species can be both remarkably stable and uniquely reactive. Here we report new classes of ligands for acylboronates that have a significant influence on the formation, properties, and reactivities of acylboronates. Our systematic investigations identified a class of neutral, monofluoroboronates that can be prepared in a one step, gram-scale fashion from readily accessible KATs. These monofluoroboronates are stable to air, moisture, and silica gel chromatography and can be easily handled without any special precautions. X-ray crystallography, NMR spectroscopy, and HPLC studies showed that they are tetravalent, configurationally stable B-chiral acylboronates. Significantly, the ligands on the boronate allow for fine-tuning of the properties and reactivity of acylboronates. In amide-forming ligation with hydroxylamines under aqueous conditions, a considerable difference in reactivity was observed as a function of ligand structure. The solid-state structures suggested that subtle steric and conformational factors modulate the reactivities of the acylboronates.
- Noda, Hidetoshi,Bode, Jeffrey W.
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supporting information
p. 3958 - 3966
(2015/04/14)
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- α1-Adrenoceptor agonists: The identification of novel α1A subtype selective 2′-heteroaryl-2-(phenoxymethyl)imidazolines
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Novel 2′-heteroaryl-2-(phenoxymethyl)imidazolines have been identified as potent agonists of the cloned human α1-adrenoceptors in vitro. The nature of the 2′-heteroaryl group can have significant effects on the potency, efficacy, and subtype selectivity in this series. α1A Subtype selective agonists have been identified.
- Bishop, Michael J.,Barvian, Kevin A.,Berman, Judd,Bigham, Eric C.,Garrison, Deanna T.,Gobel, Michael J.,Hodson, Stephen J.,Irving, Paul E.,Liacos, James A.,Navas, Iii, Frank,Saussy Jr., David L.,Speake, Jason D.
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p. 471 - 475
(2007/10/03)
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- Synthesis in 3 Azafluorene Group. Part-III
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The Hey-Elks route to arylated pyridines has been utilised in the synthesis of 3-azafluorenes.The pyrido-coumarin (23) and the related chromene (24) have been synthesised.
- Chatterjea, J. N.,Shaw, S. C.,Prasad, Y.,Singh, R. P.
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p. 1028 - 1031
(2007/10/02)
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