- A Unified Approach to Decarboxylative Halogenation of (Hetero)aryl Carboxylic Acids
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Aryl halides are a fundamental motif in synthetic chemistry, playing a critical role in metal-mediated cross-coupling reactions and serving as important scaffolds in drug discovery. Although thermal decarboxylative functionalization of aryl carboxylic acids has been extensively explored, the scope of existing halodecarboxylation methods remains limited, and there currently exists no unified strategy that provides access to any type of aryl halide from an aryl carboxylic acid precursor. Herein, we report a general catalytic method for direct decarboxylative halogenation of (hetero)aryl carboxylic acids via ligand-to-metal charge transfer. This strategy accommodates an exceptionally broad scope of substrates. We leverage an aryl radical intermediate toward divergent functionalization pathways: (1) atom transfer to access bromo- or iodo(hetero)arenes or (2) radical capture by copper and subsequent reductive elimination to generate chloro- or fluoro(hetero)arenes. The proposed ligand-to-metal charge transfer mechanism is supported through an array of spectroscopic studies.
- Blakemore, David C.,Castellano, Felix N.,Chen, Tiffany Q.,Danilov, Evgeny O.,Dechert-Schmitt, Anne-Marie,Dow, Nathan W.,Fayad, Remi,Hauke, Cory E.,Knauber, Thomas,Macmillan, David W. C.,Pedersen, P. Scott,Rosko, Michael C.
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supporting information
(2022/05/20)
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- Photoinduced catalyst-free deborylation-deuteration of arylboronic acids with D2O
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Herein, novel photoinduced catalyst-free deborylation-deuteration of arylboronic acids with D2O is reported. The protocol was compatible with a variety of functionalities, including halogen, alkoxy, cyano, sulfonyl, trimethylsilyl, trifluoromethoxy, alkyl, hydroxyl, free acid, amide, and heteroaromatic rings. A wide range of deuterated products were obtained in good yields with a high level of deuteration. This method provides a green and practical pathway to synthesize deuterium labelled compounds under mild conditions.
- Lang, Yatao,Li, Chao-Jun,Peng, Xiangjun,Zeng, Huiying
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supporting information
p. 6323 - 6327
(2020/11/09)
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- The Hexachlorocerate(III) Anion: A Potent, Benchtop Stable, and Readily Available Ultraviolet A Photosensitizer for Aryl Chlorides
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The hexachlorocerate(III) anion, [CeIIICl6]3-, was found to be a potent photoreductant in acetonitrile solution with an estimated excited-state reduction potential of - 3.45 V versus Cp2Fe0/+. Despite a short lifetime of 22.1(1) ns, the anion exhibited a photoluminescence quantum yield of 0.61(4) and fast quenching kinetics toward organohalogens allowing for its application in the photocatalytic reduction of aryl chloride substrates.
- Yin, Haolin,Jin, Yi,Hertzog, Jerald E.,Mullane, Kimberly C.,Carroll, Patrick J.,Manor, Brian C.,Anna, Jessica M.,Schelter, Eric J.
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supporting information
p. 16266 - 16273
(2016/12/27)
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- Metal-Free sp2-C-H Borylation as a Common Reactivity Pattern of Frustrated 2-Aminophenylboranes
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C-H borylation is a powerful and atom-efficient method for converting affordable and abundant chemicals into versatile organic reagents used in the production of fine chemicals and functional materials. Herein we report a facile C-H borylation of aromatic and olefinic C-H bonds with 2-aminophenylboranes. Computational and experimental studies reveal that the metal-free C-H insertion proceeds via a frustrated Lewis pair mechanism involving heterolytic splitting of the C-H bond by cooperative action of the amine and boryl groups. The adapted geometry of the reactive B and N centers results in an unprecedentently low kinetic barrier for both insertion into the sp2-C-H bond and intramolecular protonation of the sp2-C-B bond in 2-ammoniophenyl(aryl)- or -(alkenyl)borates. This common reactivity pattern serves as a platform for various catalytic reactions such as C-H borylation and hydrogenation of alkynes. In particular, we demonstrate that simple 2-aminopyridinium salts efficiently catalyze the C-H borylation of hetarenes with catecholborane. This reaction is presumably mediated by a borenium species isoelectronic to 2-aminophenylboranes.
- Chernichenko, Konstantin,Lindqvist, Markus,Kótai, Bianka,Nieger, Martin,Sorochkina, Kristina,Pápai, Imre,Repo, Timo
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supporting information
p. 4860 - 4868
(2016/05/10)
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- The thermal conversions of 6,6-difluorobicyclo[3.1.0]hex-2-enes to fluorobenzenes. An interesting dichotomy of mechanisms
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A kinetic study of the thermal, dehydrofluorinative aromatization reactions of two ostensibly-similar 6,6-difluorobicyclo[3.1.0]hex-2-ene systems led to the conclusion that drastically different mechanisms operate for the two reactions. Activation parameters, solvent effects, kinetic isotope effects, isotope labelling experiments and observation of reactive intermediates all contributed to the conclusion that the reaction of 6,6-difluorobicyclo[3.1.0]hex-2-ene, 1, proceeds via a homolytic hydrogen-shift rearrangement, while the reaction of 2,3-benzo-6,6-difluorobicyclo[3.1.0]hex-2-ene, 6, proceeds via a solvolytic mechanism involving rate-determining carbocation formation.
- Dolbier Jr.,Keaffaber,Burkholder,Koroniak,Pradhan
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p. 9649 - 9660
(2007/10/02)
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