- Insertion of Diazo Esters into C-F Bonds toward Diastereoselective One-Carbon Elongation of Benzylic Fluorides: Unprecedented BF3Catalysis with C-F Bond Cleavage and Re-formation
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Selective transformation of C-F bonds remains a significant goal in organic chemistry, but C-F insertion of a one-carbon-atom unit has never been established. Herein we report the BF3-catalyzed formal insertion of diazo esters as one-carbon-atom sources into C-F bonds to accomplish one-carbon elongation of benzylic fluorides. A DFT calculation study revealed that the BF3 catalyst could contribute to both C-F bond cleavage and re-formation. This elongation provided α-fluoro-α,β-diaryl esters with a high level of diastereoselectivity. Various benzylic fluorides and diazo esters were applicable. The synthetic utility of this method was demonstrated by the synthesis of a fluoro analogue of a compound that is used as a transient receptor and potential canonical channel inhibitor.
- Wang, Fei,Nishimoto, Yoshihiro,Yasuda, Makoto
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p. 20616 - 20621
(2021/11/23)
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- Manganese(III) 5,15-diazaporphyrins: Synthesis, properties, and catalytic use for benzylic C-H fluorination
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Fluorination of sp3 C-H bonds has attracted considerable attention as a promising method for the synthesis of organofluorine compounds. Manganese porphyrins have been extensively investigated as catalysts in the fluorination of saturated sp3 C-H bonds. Recently, we have found that iron(III) 5,15-diazaporphyrins, which are porphyrin analogues with imine-type sp2-hybridized nitrogen atoms at the meso-positions, showed high catalytic performance in the oxidation of sp3 C-H bonds. Here we disclose the synthesis, structure, and electronic properties of manganese(III) 5,15-diazaporphyrins. We also demonstrate the catalysis of chloromanganese(III) 5,15-diazaporphyrins for benzylic fluorination.
- Mori, Shiho,Nishimura, Tsubasa,Shinokubo, Hiroshi,Miyake, Yoshihiro
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p. 991 - 996
(2021/08/23)
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- Copper-Catalyzed Functionalization of Benzylic C-H Bonds with N-Fluorobenzenesulfonimide: Switch from C-N to C-F Bond Formation Promoted by a Redox Buffer and Br?nsted Base
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A copper catalyst in combination with N-fluorobenzenesulfonimide (NFSI) has been reported to functionalize benzylic C-H bonds to the corresponding benzylic sulfonimides via C-N coupling. Here, we reported a closely related Cu-catalyzed method with NFSI that instead leads to C-F coupling. This switch in selectivity arises from changes to the reaction conditions (Cu/ligand ratio, temperature, addition of base) and further benefits from inclusion of MeB(OH)2 in the reaction. MeB(OH)2 is shown to serve as a "redox buffer"in the reaction, responsible for rescuing inactive Cu(II) for continued promotion of fluorination reactivity.
- Buss, Joshua A.,Golden, Dung L.,Stahl, Shannon S.,Vasilopoulos, Aristidis
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supporting information
p. 5749 - 5752
(2020/10/02)
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- Copper-Catalyzed C-H Fluorination/Functionalization Sequence Enabling Benzylic C-H Cross Coupling with Diverse Nucleophiles
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Site-selective transformation of benzylic C-H bonds into diverse functional groups is achieved via Cu-catalyzed C-H fluorination with N-fluorobenzenesulfonimide (NFSI), followed by substitution of the resulting fluoride with various nucleophiles. The benzyl fluorides generated in these reactions are reactive electrophiles in the presence of hydrogen-bond donors or Lewis acids, allowing them to be used without isolation in C-O, C-N, and C-C coupling reactions.
- Buss, Joshua A.,Golden, Dung L.,Stahl, Shannon S.,Vasilopoulos, Aristidis
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supporting information
(2020/08/24)
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- METHODS AND COMPOSITIONS FOR DIRECT RADIOACTIVE LABELING OF BIO-ACTIVE MOLECULES AND BUILDING BLOCKS
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Methods of direct radioactive labeling a carbon containing compound having an sp3 C-H bond are provided. Methods of carrier-free 18F fluorination of a carbon containing compound mediated by manganese salen complexes or manganese porphyrin complexes comprising weakly coordinated anions as axial ligands are provided. Methods of "dry-down" free radioactive labeling of a carbon containing compound having an sp3 C-H bond are provided. The radioactively labeled products of the methods are provided.
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Paragraph 00119; 00120; 00121
(2015/11/02)
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- Cis-specific hydrofluorination of alkenylarenes under palladium catalysis through an ionic pathway
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This paper describes the hydrofluorination of alkenes through sequential H- and F+ addition under palladium catalysis. The reaction is cis specific, thus providing access to benzylic fluorides. The mechanism of this reaction involves an ionic pathway and is distinct from known hydrofluorinations involving radical intermediates. The first catalytic enantioselective hydrofluorination is also disclosed. See attached PdF: A series of benzylic fluorides was prepared by hydrofluorination which proceeds through a PdII/IV catalytic manifold. The method is mechanistically distinct from previously reported radical hydrofluorination, and is characterized by its clean regioselectivity and unique cis stereospecificity. The first example of enantioselective net HF addition onto 2-vinylnaphthalene is also disclosed.
- Emer, Enrico,Pfeifer, Lukas,Brown, John M.,Gouverneur, Veronique
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supporting information
p. 4181 - 4185
(2014/05/06)
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- A continuous-flow protocol for light-induced benzylic fluorinations
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A continuous-flow protocol for the light-induced fluorination of benzylic compounds is presented. The procedure uses Selectfluor as the fluorine source and xanthone as an inexpensive and commercially available photoorganocatalyst. The flow photoreactor is based on transparent fluorinated ethylene propylene tubing and a household compact fluorescent lamp. The combination of xanthone with black-light irradiation results in very efficient fluorination. Good to excellent isolated yields were obtained for a variety of substrates bearing different functional groups applying residence times below 30 min.
- Cantillo, David,De Frutos, Oscar,Rincón, Juan A.,Mateos, Carlos,Kappe, C. Oliver
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p. 8486 - 8490
(2015/03/18)
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- Late stage benzylic C-H fluorination with [18F]fluoride for PET imaging
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We describe the first late-stage 18F labeling chemistry for aliphatic C-H bonds with no-carrier-added [18F]fluoride. The method uses Mn(salen)OTs as an F-transfer catalyst and enables the facile labeling of a variety of bioactive molecules and building blocks with radiochemical yields (RCY) ranging from 20% to 72% within 10 min without the need for preactivation of the labeling precursor. Notably, the catalyst itself can directly elute [18F]fluoride from an ion exchange cartridge with over 90% efficiency. Using this feature, the conventional and laborious dry-down step prior to reaction is circumvented, greatly simplifying the mechanics of this protocol and shortening the time for automated synthesis. Eight drug molecules, including COX, ACE, MAO, and PDE inhibitors, have been successfully [ 18F]-labeled in this way.
- Huang, Xiongyi,Liu, Wei,Ren, Hong,Neelamegam, Ramesh,Hooker, Jacob M.,Groves, John T.
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supporting information
p. 6842 - 6845
(2014/06/09)
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- Manganese-catalyzed oxidative benzylic C-H fluorination by fluoride ions
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An efficient protocol for the selective fluorination of benzylic C-H bonds is described. The process is catalyzed by manganese salen complexes and uses nucleophilic fluorine sources, such as triethylamine trihydrofluoride and KF. Reaction rates are sufficiently high (30min) to allow adoption for the incorporation of 18F fluoride sources for PET imaging applications. Copyright
- Liu, Wei,Groves, John T.
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supporting information
p. 6024 - 6027
(2013/07/04)
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- Synthesis of optically active 1-fluoroalkyl benzenes
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A simple synthesis of optically active 1-fluoroalkyl benzenes bearing electron withdrawing substituents is developed. Optically active 1- hydroxyalkyl benzenes are converted into the methanesulfonates and subsequently converted into the optically active 1-fluoroalkyl benzenes 1 by use of the fluorinating agent cesium fluoride/N-methyl-formamide.
- Fritz-Langhals, Elke
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p. 1851 - 1854
(2007/10/02)
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