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Kucharski MM, Watson AJB, Lloyd-Jones GC. Speciation and kinetics of fluoride transfer from tetra- n-butylammonium difluorotriphenylsilicate ('TBAT'). Chem Sci 2024; 15:4331-4340. [PMID: 38516098 PMCID: PMC10952091 DOI: 10.1039/d3sc05776c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2023] [Accepted: 12/06/2023] [Indexed: 03/23/2024] Open
Abstract
Tetra-n-butylammonium difluorotriphenylsilicate (TBAT) is a conveniently handled anhydrous fluoride source, commonly used as a surrogate for tetra-n-butylammonium fluoride (TBAF). While prior studies indicate that TBAT reacts rapidly with fluoride acceptors, little is known about the mechanism(s) of fluoride transfer. We report on the interrogation of the kinetics of three processes in which fluoride is transferred from TBAT, in THF and in MeCN, using a variety of NMR methods, including chemical exchange saturation transfer, magnetisation transfer, diffusion analysis, and 1D NOESY. These studies reveal ion-pairing between the tetra-n-butylammonium and difluorotriphenylsilicate moieties, and a very low but detectable degree of fluoride dissociation, which then undergoes further equilibria and/or induces decomposition, depending on the conditions. Degenerate exchange between TBAT and fluorotriphenylsilane (FTPS) is very rapid in THF, inherently increases in rate over time, and is profoundly sensitive to the presence of water. Addition of 2,6-di-tert-butylpyridine and 3 Å molecular sieves stabilises the exchange rate, and both dissociative and direct fluoride transfer are shown to proceed in parallel under these conditions. Degenerate exchange between TBAT and 2-naphthalenyl fluorosulfate (ARSF) is not detected at the NMR timescale in THF, and is slow in MeCN. For the latter, the exchange is near-fully inhibited by exogenous FTPS, indicating a predominantly dissociative character to this exchange process. Fluorination of benzyl bromide (BzBr) with TBAT in MeCN-d3 exhibits moderate progressive autoinhibition, and the initial rate of the reaction is supressed by the presence of exogenous FTPS. Overall, TBAT can act as a genuine surrogate for TBAF, as well as a reservoir for rapidly-reversible release of traces of it, with the relative contribution of the pathways depending, inter alia, on the identity of the fluoride acceptor, the solvent, and the concentration of endogenous or exogenous FTPS.
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Affiliation(s)
- Maciej M Kucharski
- School of Chemistry, University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
| | - Allan J B Watson
- School of Chemistry, University of St Andrews North Haugh, St Andrews KY16 9ST UK
| | - Guy C Lloyd-Jones
- School of Chemistry, University of Edinburgh David Brewster Road Edinburgh EH9 3FJ UK
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Nair RR, Seo EW, Hong S, Jung KO, Kim D. Pentafluorobenzene: Promising Applications in Diagnostics and Therapeutics. ACS APPLIED BIO MATERIALS 2023; 6:4081-4099. [PMID: 37721519 DOI: 10.1021/acsabm.3c00676] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2023]
Abstract
Pentafluorobenzene (PFB) represents a class of aromatic fluorine compounds employed exclusively across a spectrum of chemical and biological applications. PFBs are credited with developing various chemical synthesis techniques, networks and biopolymers, bioactive materials, and targeted drug delivery systems. The first part of this review delves into recent developments in PFB-derived molecules for diagnostic purposes. In the latter segment, PFB's role in the domain of theragnostic applications is discussed. The review elucidates different mechanisms and interaction strategies applied in leveraging PFBs to formulate diagnostic and theragnostic tools, substantiated by proper examples. The utilization of PFBs emerges as an enabler, facilitating manifold reactions, improving materials' properties, and even opening avenues for explorative research.
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Affiliation(s)
- Ratish R Nair
- Medical Research Center for Bioreaction to Reactive Oxygen Species and Biomedical Science Institute, Core Research Institute (CRI), Kyung Hee University, Seoul 02447, Republic of Korea
| | - Eun Woo Seo
- Department of Biomedical Science, Graduate School, Kyung Hee University, Seoul 02447, Republic of Korea
| | - Seongje Hong
- Department of Anatomy, College of Medicine, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Kyung Oh Jung
- Department of Anatomy, College of Medicine, Chung-Ang University, Seoul 06974, Republic of Korea
| | - Dokyoung Kim
- Medical Research Center for Bioreaction to Reactive Oxygen Species and Biomedical Science Institute, Core Research Institute (CRI), Kyung Hee University, Seoul 02447, Republic of Korea
- Department of Biomedical Science, Graduate School, Kyung Hee University, Seoul 02447, Republic of Korea
- Department of Anatomy and Neurobiology, College of Medicine, Kyung Hee University, Seoul 02447, Republic of Korea
- Center for Converging Humanities, Kyung Hee University, Seoul 02447, Republic of Korea
- KHU-KIST Department of Converging Science and Technology, Kyung Hee University, Seoul 02447, Republic of Korea
- UC San Diego Materials Research Science and Engineering Center, 9500 Gilman Drive, La Jolla, California 92093, United States
- Center for Brain Technology, Brain Science Institute, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea
- Department of Precision Medicine, Graduate School, Kyung Hee University, Seoul 02447, Republic of Korea
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Zhang JQ, Hu D, Wang J, Ni B, Ren H. Bimetallic Metal-Organic Coordination Polymers Facilitated the Selective C-F Cleavage of Polyfluoroarenes. Org Lett 2022; 24:7905-7911. [PMID: 36269221 DOI: 10.1021/acs.orglett.2c02918] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Selective C-F bond cleavage of polyfluoroarenes has attracted tremendous interest due to its promising applications in introducing fluorinated building blocks into organic molecules. However, it remains a challenge to achieve highly site-selective C-F bond cleavage because of the intrinsic inertness of the C-F bond and the difficulty in distinguishing specific C-F bonds on the aromatic ring. Herein we report an efficient nucleophilic aromatic substitution (SNAr) reaction of polyfluoroarenes with Grignard reagents that employs MnFe-based bimetallic metal-organic coordination polymers (MOCPs) as recyclable and reusable heterogeneous catalysts. Significantly, in this reaction, the prepared MOCP (Mn-Fe) catalyst exhibited excellent activity in selective C-F bond cleavage and afforded a series of functionalized polyfluoroarenes in moderate to excellent yields (up to 96%). This work highlights the potential of MOCP catalysts to serve as a tunable platform in Lewis acid catalysis.
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Affiliation(s)
- Jun-Qi Zhang
- Advanced Research Institute and Department of Chemistry, Taizhou University, Jiaojiang 318000, China
| | - Dandan Hu
- Advanced Research Institute and Department of Chemistry, Taizhou University, Jiaojiang 318000, China
| | - Jiali Wang
- Advanced Research Institute and Department of Chemistry, Taizhou University, Jiaojiang 318000, China
| | - Bukuo Ni
- Department of Chemistry, Texas A&M University-Commerce, Commerce, Texas 75429-3011, United States
| | - Hongjun Ren
- Advanced Research Institute and Department of Chemistry, Taizhou University, Jiaojiang 318000, China.,School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang 453000, China
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Funabiki K, Yamada K, Arisawa Y, Watanabe A, Agou T, Kubota Y, Inuzuka T, Miwa Y, Udagawa T, Kutsumizu S. Design, Regioselective Synthesis, and Photophysical Properties of Perfluoronaphthalene-Based Donor-Acceptor-Donor Fluorescent Dyes. J Org Chem 2022; 87:11751-11765. [PMID: 36001449 DOI: 10.1021/acs.joc.2c01446] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A one-step route to a series of perfluoronaphthalene-based donor (D)-acceptor (A)-D fluorescent dyes with various electron-donating groups was developed. The perfluoronaphthalene moiety in the D-A-D dyes served as a good electron-accepting aromatic ring with excellent intramolecular charge transfer properties, as determined by density functional theory calculations and measurements of the fluorescence properties in solution, in poly(methyl methacrylate) (PMMA) films, and in crystal form. Notably, replacing the naphthalene ring with perfluoronaphthalene in the D-A-D dyes carrying the phenothiazine moiety not only stabilized the highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels but also reduced the energy band gap to change the emission color from blue to yellow. Among the four synthesized perfluoronaphthalene D-A-D dyes, those bearing diphenylamino groups afforded the best fluorescence quantum yields in Et2O solution (0.60) and in PMMA film (0.65) because the propeller structure of the diphenylamino group that acts as a donor substituent effectively suppresses radiation-free deactivation. In contrast, in the crystalline state, the carbazoyl-bearing D-A-D dye provided the best fluorescence quantum yield (0.35) because the radiation-free inactivation was suppressed by π-πF stacking at the donor site, which was confirmed by single-crystal X-ray analysis.
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Affiliation(s)
- Kazumasa Funabiki
- Department of Chemistry and Biomolecular Science, Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan
| | - Kengo Yamada
- Department of Chemistry and Biomolecular Science, Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan
| | - Yuta Arisawa
- Department of Chemistry and Biomolecular Science, Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan
| | - Arina Watanabe
- Department of Chemistry and Biomolecular Science, Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan
| | - Tomohiro Agou
- Department of Biomolecular Functional Engineering, Ibaraki University, 4-12-1 Nakanarusawa, Hitachi 316-8511, Japan
| | - Yasuhiro Kubota
- Department of Chemistry and Biomolecular Science, Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan
| | - Toshiyasu Inuzuka
- Division of Instrumental Analysis, Life Science Research Center, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
| | - Yohei Miwa
- Department of Chemistry and Biomolecular Science, Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan
| | - Taro Udagawa
- Department of Chemistry and Biomolecular Science, Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan
| | - Shoichi Kutsumizu
- Department of Chemistry and Biomolecular Science, Gifu University, 1-1, Yanagido, Gifu 501-1193, Japan
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Regioselective Transfer Hydrogenative Defluorination of Polyfluoroarenes Catalyzed by Bifunctional Azairidacycle. ORGANICS 2022. [DOI: 10.3390/org3030012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
The catalytic hydrodefluorination (HDF) with a bifunctional azairidacycle using HCOOK was examined for cyano- and chloro-substituted fluoroarenes, including penta- and tetrafluorobenzonitriles, tetrafluoroterephthalonitrile, tetrafluorophthalonitrile, 3-chloro-2,4,5,6-tetrafluoropyridine, and 4-cyano-2,3,5,6-tetrafluoropyridine. The reaction was performed in the presence of a controlled amount of HCOOK with a substrate/catalyst ratio (S/C) of 100 in a 1:1 mixture of 1,2-dimethoxyethane (DME) and H2O at an ambient temperature of 30 °C to obtain partially fluorinated compounds with satisfactory regioselectivities. The C–F bond cleavage proceeded favorably at the para position of substituents other than fluorine, which is in consonance with the nucleophilic aromatic substitution mechanism. In the HDF of tetrafluoroterephthalonitrile and 4-cyano-2,3,5,6-tetrafluoropyridine, which do not contain a fluorine atom at the para position of the cyano group, the double defluorination occurred solely at the 2- and 5-positions, as confirmed by X-ray crystallography. The HDF of 3-chloro-2,4,5,6-tetrafluoropyridine gave preference to the C–F bond cleavage over the C–Cl bond cleavage, unlike the dehalogenation pathway via electron-transfer radical anion fragmentation. In addition, new azairidacycles with an electron-donating methoxy substituent on the C–N chelating ligand were synthesized and served as a catalyst precursor (0.2 mol%) for the transfer hydrogenative defluorination of pentafluoropyridine, leading to 2,3,5,6-tetrafluoropyridine with up to a turnover number (TON) of 418.
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