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Trojan M, Hroch A, Gruden E, Cvačka J, Čejka J, Tavčar G, Rybáčková M, Kvíčala J. Modified aryldifluorophenylsilicates with improved activity and selectivity in nucleophilic fluorination of secondary substrates. RSC Adv 2024; 14:22326-22334. [PMID: 39010913 PMCID: PMC11247957 DOI: 10.1039/d4ra04332d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2024] [Accepted: 07/04/2024] [Indexed: 07/17/2024] Open
Abstract
Nucleophilic fluorination of secondary aliphatic substrates, especially of halides, still remains a challenge. Among the available reagents, TBAT belongs to one of the best choices due to its stability, affordable price and low toxicity. With the aim to improve its selectivity, we synthesized three analogues modified in the aryl part of the TBAT reagent with one or two electron donating methoxy groups or with one electron withdrawing trifluoromethyl group. All three reagents are air-stable compounds and their structure was confirmed by a single crystal X-ray analysis. In testing the reactivity and selectivity of the reagents with a library of secondary bromides, as well as of other selected primary and secondary substrates, we found that substitution with methoxy groups mostly improves both reactivity and selectivity compared to TBAT, while the substitution with trifluoromethyl group leads to inferior results. Difluorosilicates modified by more than two electron donating methoxy groups proved to be unstable and decomposed spontaneously to the HF2 - anion. DFT calculations of tetramethylammonium analogues of the studied reagents disclosed that the substitution of the phenyl group with the methoxy substituent lowers the transitions state energy of the decomposition to a fluorosilane-fluoride complex, while the substitution with the trifluoromethyl group has an opposite effect.
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Affiliation(s)
- Michal Trojan
- Department of Organic Chemistry, University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
| | - Adam Hroch
- Department of Organic Chemistry, University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
| | - Evelin Gruden
- Department of Inorganic Chemistry and Technology, "Jožef Stefan" Institute Jamova Cesta 39 Ljubljana Slovenia
| | - Josef Cvačka
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences Flemingovo Náměstí 542/2 160 00 Prague 6 Czech Republic
| | - Jan Čejka
- Department of Solid State Chemistry, University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
| | - Gašper Tavčar
- Department of Inorganic Chemistry and Technology, "Jožef Stefan" Institute Jamova Cesta 39 Ljubljana Slovenia
| | - Markéta Rybáčková
- Department of Organic Chemistry, University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
| | - Jaroslav Kvíčala
- Department of Organic Chemistry, University of Chemistry and Technology, Prague Technická 5 166 28 Prague 6 Czech Republic
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Trojan M, Kučnirová K, Bouzková Š, Cvačka J, Čejka J, Tavčar G, Rybáčková M, Kvíčala J. Quaternary ammonium fluorides and difluorosilicates as nucleophilic fluorination reagents. Org Biomol Chem 2024; 22:1047-1056. [PMID: 38197465 DOI: 10.1039/d3ob01875j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
TBAT (tetrabutylammonium difluorotriphenylsilicate) is an excellent homogeneous nucleophilic fluorination reagent, but a high excess of the reagent was reported to be essential. We hence optimized the reaction conditions and compared its nucleophilic fluorination reactivity with that of other common commercial nucleophilic fluorination reagents, such as anhydrous TBAF and TASF (tris(dimethylamino)sulfonium difluorotrimethylsilicate). As the substrates, we employed a standard set of primary and secondary octyl substrates under identical conditions. To eliminate the possibility of hydrogen fluoride elimination in the above reagents, we prepared four quaternary ammonium fluorides lacking β-elimination possibility in the hydrocarbon chain, transformed them to the corresponding difluorotriphenylsilicates, and compared their reactivity with that of the commercial reagents. Furthermore, attempts to isolate analogous tetrabutylammonium difluoromethyldiphenylsilicate or difluorodimethylphenylsilicate failed, as was confirmed by comparison of the published experimental data with computed 19F NMR spectra. Finally, we studied the transition states of decomposition of various tetramethylammonium methylphenyldifluorosilicates by DFT methods and found that their relative energies increase with an increasing number of phenyl groups. The formation of difluorosilicates is a nearly barrierless process.
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Affiliation(s)
- Michal Trojan
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
| | - Kateřina Kučnirová
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
| | - Šárka Bouzková
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
| | - Josef Cvačka
- Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo náměstí 542/2, 160 00 Prague 6, Czech Republic
| | - Jan Čejka
- Department of Solid State Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic
| | - Gašper Tavčar
- Department of Inorganic Chemistry and Technology, "Jožef Stefan" Institute, Jamova cesta 39, Ljubljana, Slovenia
| | - Markéta Rybáčková
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
| | - Jaroslav Kvíčala
- Department of Organic Chemistry, University of Chemistry and Technology, Prague, Technická 5, 166 28 Prague 6, Czech Republic.
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Karuo Y, Tarui A, Sato K, Kawai K, Omote M. Reactions Using Freons and Halothane as Halofluoroalkyl/Halofluoroalkenyl Building Blocks. CHEM REC 2023; 23:e202300029. [PMID: 37017496 DOI: 10.1002/tcr.202300029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 03/15/2023] [Indexed: 04/06/2023]
Abstract
In recent years, hydrofluorocarbon compounds such as chlorofluorocarbons, hydrochlorofluorocarbons, and 2-bromo-2-chloro-1,1,1-trifluoroethane (halothane) have been used as fluorine-containing building blocks to construct functional fluorine-containing compounds, e. g., polymers, liquid crystals, and medicines. Hydrofluorocarbons promote the formation of reactive fluoroalkyl or fluoroalkenyl species via anionic or radical processes, and these species can act as nucleophiles or electrophiles depending on the reaction conditions. Progress in fluorine chemistry using hydrofluorocarbons in the last 30 years is described in this review and diverse reactions are discussed, including the fluoroalkyl/alkenyl products and proposed mechanisms involved.
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Affiliation(s)
- Yukiko Karuo
- Faculty of Pharmaceutical Sciences, Setsunan University, 45-1, Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
| | - Atushi Tarui
- Faculty of Pharmaceutical Sciences, Setsunan University, 45-1, Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
| | - Kazuyuki Sato
- Faculty of Pharmaceutical Sciences, Setsunan University, 45-1, Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
| | - Kentaro Kawai
- Faculty of Pharmaceutical Sciences, Setsunan University, 45-1, Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
| | - Masaaki Omote
- Faculty of Pharmaceutical Sciences, Setsunan University, 45-1, Nagaotoge-cho, Hirakata, Osaka, 573-0101, Japan
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Khandelwal M, Pemawat G, Khangarot RK. Recent Developments in Nucleophilic Fluorination with Potassium Fluoride (KF): A Review. ASIAN J ORG CHEM 2022. [DOI: 10.1002/ajoc.202200325] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Manisha Khandelwal
- Mohanlal Sukhadia University Department of Chemistry UCOS, Durga Nursery Road 313001 Udaipur INDIA
| | - Gangotri Pemawat
- Mohanlal Sukhadia University Department of Chemistry UCOS, Durga Nursery Road 313001 Udaipur INDIA
| | - Rama Kanwar Khangarot
- Mohanlal Sukhadia University Department of Chemistry UCOS, Durga Nursery Road 313001 Udaipur INDIA
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Lisboa FM, Pliego JR. S N2 versus E2 reactions in a complex microsolvated environment: theoretical analysis of the equilibrium and activation steps of a nucleophilic fluorination. J Mol Model 2022; 28:159. [PMID: 35596807 DOI: 10.1007/s00894-022-05160-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 05/12/2022] [Indexed: 10/18/2022]
Abstract
The reactivity of the fluoride ion towards alkyl halides is highly dependent on the solvating environment. In polar aprotic solvents with large counter-ions is highly reactive and produces substantial E2 product, whereas in polar protic solvents leads to slow kinetics and high selectivity for SN2 reactions. The use of a more complex environment with stoichiometric addition of tert-butanol to acetonitrile solvent is able to module the reactivity and selectivity of tetrabutylammonium fluoride (TBAF). In the present work, we have performed a detailed theoretical analysis of this complex reaction system by density functional theory, continuum solvation model, and including explicit tert-butanol molecules. A kinetic model based on the free energy profile was also used to predict the reactivity and selectivity. The results indicated that the TBAF(tert-butanol) complex plays the key role to increase the SN2 selectivity, whereas higher aggregates are not relevant. The E2 product is formed exclusively via free TBAF, because the solvating tert-butanol in the TBAF(tert-butanol) complex inhibits the E2 pathway. Our analysis suggests that diols or tetraols could produce an improved selectivity.
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Affiliation(s)
- Fernando M Lisboa
- Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, São João del-Rei, MG, 36301-160, Brazil
| | - Josefredo R Pliego
- Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, São João del-Rei, MG, 36301-160, Brazil.
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Copper-Mediated Aromatic Fluorination Using N-Heterocycle-Carbene Ligand: Free Energy Profile of the Cu(I)/Cu(III) and Cu(II) radical Mechanisms. J Organomet Chem 2022. [DOI: 10.1016/j.jorganchem.2022.122397] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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7
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Liu ZL, Xu JX, Deng N, Dong Z, Shen X, Xu J, Xu HJ. Coupling of Thiols and Aryl Halides Mediated by Dicyclohexano-18-Crown-6 and Potassium Carbonate. Curr Org Synth 2022; 19:824-837. [PMID: 35418286 DOI: 10.2174/1570179419666220412084111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Revised: 01/26/2022] [Accepted: 02/03/2022] [Indexed: 11/22/2022]
Abstract
AIMS A simple, transition-metal-free C-S coupling protocol for the synthesis of aryl thioethers is reported Background: Sulfur-containing moieties are ubiquitous in pharmaceutical drugs and materials and therefore methods for their construction are of great importance. One approach entails the catalytic coupling of an aryl halohydrocarbon with a thiol, but the transition metal catalysts usually used are prone to poisoning by participating sulfur species and efficient catalysis is usually only achieved after complex ligand optimization. OBJECTIVE New transition-metal-free approaches to the synthesis of C-S bonds are urgently need Method: We screened the reaction conditions such as alkali, crown ether, solvent, temperature, etc., tested the compatibility of the reaction substrate, and analyzed the mechanism process. RESULT the optimized reaction conditions were determined to be 1.0 equiv of aryl halides and 1.2 equiv of thiols at 110 ℃ in toluene with K2CO3 (1.5 equiv) as a base, promoted by 10 mol% dicyclohexano-18-crown-6. Up to 33 examples of thioethers were synthesized under transition-metal-free conditions in good to excellent yields. CONCLUSION we have developed a simple and efficient method for the C-S cross-coupling of a wide variety of (hetero)aryl halides and thiols mediated by dicyclohexano-18-crown-6 and without the need for transition-metal catalyst. In addition, the preparation and gram-scale experiments of a variety of drug molecules further verify the practicability of our developed method.
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Affiliation(s)
- Zhong-Lin Liu
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering, Anhui Province Key Laboratory of Advance Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China
| | - Jing-Xiu Xu
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering, Anhui Province Key Laboratory of Advance Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China
| | - Ning Deng
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering, Anhui Province Key Laboratory of Advance Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China
| | - Zheng Dong
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering, Anhui Province Key Laboratory of Advance Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China
| | - Xiao Shen
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering, Anhui Province Key Laboratory of Advance Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China
| | - Jun Xu
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering, Anhui Province Key Laboratory of Advance Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China
| | - Hua-Jian Xu
- School of Food and Biological Engineering, School of Chemistry and Chemical Engineering, Anhui Province Key Laboratory of Advance Catalytic Materials and Reaction Engineering, Hefei University of Technology, Hefei 230009, China
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Mykhailiuk PK. Fluorine-Containing Prolines: Synthetic Strategies, Applications, and Opportunities. J Org Chem 2022; 87:6961-7005. [PMID: 35175772 DOI: 10.1021/acs.joc.1c02956] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Fluorinated prolines play an important role in peptide studies, protein engineering, medicinal chemistry, drug discovery, and agrochemistry. Since the first synthesis of 4-fluoroprolines by Gottlieb and Witkop in 1965, their popularity started to grow exponentially. For example, during the past two decades, all isomeric trifluoromethyl-substituted prolines have been synthesized. In this Perspective, chemical properties and applications of fluorinated prolines are discussed. Synthetic approaches to all known fluorine-containing prolines are also discussed and analyzed. This analysis unexpectedly revealed an unsolved problem: in strict contrast to fluoro- and trifluoromethyl-substituted prolines, the corresponding analogues with fluoromethyl and difluoromethyl groups are mostly unknown. At the end of the paper, structures of several interesting, yet unknown, fluorinated prolines are disclosed─a good opportunity for chemists to make them.
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Li W, Lu Z, Hammond GB, Xu B. Unbalanced-Ion-Pair-Catalyzed Nucleophilic Fluorination Using Potassium Fluoride. Org Lett 2021; 23:9640-9644. [PMID: 34851641 DOI: 10.1021/acs.orglett.1c03887] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An unbalanced ion pair promoter (e.g., tetrabutylammonium sulfate), consisting of a bulky and charge-delocalized cation and a small and charge-localized anion, greatly accelerates nucleophilic fluorinations using easy handling KF. We also successfully converted an inexpensive and commercially available ion-exchange resin to the polymer-supported ion pair promoter (A26-SO42-), which could be reused after filtration. Moreover, A26-SO42- can be used in continuous flow conditions. In our conditions, water is well-tolerated.
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Affiliation(s)
- Wangbing Li
- Key Laboratory of Science and Technology of Eco-Textiles, Ministry of Education, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, 201620, China
| | - Zhichao Lu
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, United States
| | - Gerald B Hammond
- Department of Chemistry, University of Louisville, Louisville, Kentucky 40292, United States
| | - Bo Xu
- Key Laboratory of Science and Technology of Eco-Textiles, Ministry of Education, College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, 201620, China
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11
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Phenol alkylation under phase transfer catalysis conditions: Insights on the mechanism and kinetics from computations. MOLECULAR CATALYSIS 2021. [DOI: 10.1016/j.mcat.2021.111566] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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12
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Catalytic cycle and off-cycle steps in the palladium-catalyzed fluorination of aryl bromide with biaryl monophosphine ligands: Theoretical free energy profile. MOLECULAR CATALYSIS 2021. [DOI: 10.1016/j.mcat.2021.111540] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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13
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Zheng Y, Xie ZZ, He XC, Chen YS, Cheng WS, Chen K, Xiang HY, Chen XQ, Yang H. Phosphonium Ylide-Mediated Programmable Fluorination to Access Mono- and Difluoromethylarenes. Org Lett 2021; 23:2538-2542. [DOI: 10.1021/acs.orglett.1c00457] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yu Zheng
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China
| | - Zhen-Zhen Xie
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China
| | - Xian-Chen He
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China
| | - Yan-Shan Chen
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China
| | - Wen-Shuo Cheng
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China
| | - Kai Chen
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China
| | - Hao-Yue Xiang
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China
| | - Xiao-Qing Chen
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China
| | - Hua Yang
- College of Chemistry and Chemical Engineering, Central South University, Changsha 410083, P. R. China
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Pliego JR. The role of intermolecular forces in ionic reactions: the solvent effect, ion-pairing, aggregates and structured environment. Org Biomol Chem 2021; 19:1900-1914. [PMID: 33554992 DOI: 10.1039/d0ob02413a] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The environment enclosing an ionic species has a critical effect on its reactivity. In a more general sense, medium effects are not limited to the solvent, but involve the counter ion effect (ion pairing), formation of larger aggregates and structured environment as provided by the host in the case of host-guest complexes. In this review, a general view of the medium effect on anion-molecule reactions is presented. Nucleophilic substitution reactions of aliphatic (SN2) and aromatic (SNAr) systems, as well as elimination reactions (E2), are the focus of the discussion. In particular, nucleophilic fluorination with KF, CsF and tetraalkylammonium fluoride was used as the main model, because of the importance of this kind of reaction and the recent advances in the study of these systems. The solvent effect, ion pairing, formation of aggregates and formation of complexes with crown ethers, cryptands and calixarenes are discussed. For a deeper insight into the medium effect, many results of reliable theoretical calculations in close agreement with experiments were chosen as examples.
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Affiliation(s)
- Josefredo R Pliego
- Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, 36301-160, São João del-Rei, MG, Brazil.
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15
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Lee WC, Kang SM, Lee BC, Kim SE, Kim DW. Multifunctional Crown-5-calix[4]arene-based Phase-Transfer Catalysts for Aromatic 18F-Fluorination. Org Lett 2020; 22:9551-9555. [PMID: 33270463 DOI: 10.1021/acs.orglett.0c03604] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Methylated bis-triethylene glycolic crown-5-calix[4]arene (M-BTC5A) as a phase-transfer catalyst showed the best performance among other analogues and even conventional Kryptofix 222 in the nucleophilic aromatic 18F-fluorination of diaryliodonium tosylate precursors owing to (i) the efficient release of reactive "naked" [18F]fluoride, (ii) the high stabilization of the precursor in the reaction, and, presumably, (iii) the ease of access between the precursor and the K18F/M-BTC5A complex facilitated by π-π interactions. [18F]Flumazenil was produced in high radiochemical yield using M-BTC5A.
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Affiliation(s)
- Won Chang Lee
- Department of Nuclear Medicine, Seoul National University Hospital, Seongnam 13620, Republic of Korea.,Department of Transdisciplinary Studies, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 08826, Republic of Korea
| | - Seok Min Kang
- Department of Chemistry and Chemical Engineering, Inha University, Incheon 22212, Republic of Korea
| | - Byung Chul Lee
- Department of Nuclear Medicine, Seoul National University Hospital, Seongnam 13620, Republic of Korea.,Center for Nanomolecular Imaging and Innovative Drug Development, Advanced institutes of Convergence Technology, Suwon 16229, Republic of Korea
| | - Sang Eun Kim
- Department of Nuclear Medicine, Seoul National University Hospital, Seongnam 13620, Republic of Korea.,Center for Nanomolecular Imaging and Innovative Drug Development, Advanced institutes of Convergence Technology, Suwon 16229, Republic of Korea.,Department of Molecular and Biophamaceutical Sciences, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 08826, Republic of Korea
| | - Dong Wook Kim
- Department of Chemistry and Chemical Engineering, Inha University, Incheon 22212, Republic of Korea
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Micro-solvation and counter ion effects on ionic reactions: Activation of potassium fluoride with 18-crown-6 and tert-butanol in aprotic solvents. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114211] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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17
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Silva SL, Valle MS, Pliego JR. Nucleophilic Fluorination with KF Catalyzed by 18-Crown-6 and Bulky Diols: A Theoretical and Experimental Study. J Org Chem 2020; 85:15457-15465. [PMID: 33227195 DOI: 10.1021/acs.joc.0c02229] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The activation of potassium fluoride for nucleophilic fluorination of alkyl halides is an important challenge because of the high lattice energy of this salt and its low solubility in many polar aprotic solvents. Crown ethers have been used for increasing the solubilization of KF during several decades. Nevertheless, these macrocycles are not enough to produce a high reaction rate. In this work, theoretical methods were used for designing a synergic combination of bulky diols with crown ethers able to accelerate this kind of reaction. The calculations have predicted that the bulky diol 1,4-Bis(2-hydroxy-2-propyl)benzene, which has distant hydroxyl groups, is able to catalyze nucleophilic fluorination in combination with 18-crown-6 via two hydrogen bonds to the SN2 transition state. Experimental studies following the theoretical predictions have confirmed the catalytic effect and the estimated kinetic data point out that the bulky diol at 1 mol L-1 in combination with 18-crown-6 is able to produce an 18-fold increase in the reaction rate in relation to crown ether catalysis only. The reaction produces 46% yield of fluorination after 24 h at moderate temperature of 82 °C, with minimal formation of the side elimination product. Thus, this work presents an improved method for fluorination with KF salt.
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Affiliation(s)
- Samuel L Silva
- Departamento de Ciências Naturais, Universidade Federal de Säo Joäo del-Rei, Säo Joäo del-Rei, 36301-160 MG, Brazil
| | - Marcelo S Valle
- Departamento de Ciências Naturais, Universidade Federal de Säo Joäo del-Rei, Säo Joäo del-Rei, 36301-160 MG, Brazil
| | - Josefredo R Pliego
- Departamento de Ciências Naturais, Universidade Federal de Säo Joäo del-Rei, Säo Joäo del-Rei, 36301-160 MG, Brazil
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Sayed M, Hiraishi N, Matin K, Abdou A, Burrow MF, Tagami J. Effect of silver-containing agents on the ultra-structural morphology of dentinal collagen. Dent Mater 2020; 36:936-944. [DOI: 10.1016/j.dental.2020.04.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 04/15/2020] [Accepted: 04/30/2020] [Indexed: 01/04/2023]
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19
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The Effects of Structural Modifications of Bis-tert-
alcohol-Functionalized Crown-Calix[4]arenes as Nucleophilic Fluorination Promotors and Relations with Computational Predictions. European J Org Chem 2020. [DOI: 10.1002/ejoc.201901746] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Pliego JR. Free Energy Profile of a Model Palladium Catalyzed Fluorination of Aryl Bromide with Cesium Fluoride. J Phys Chem A 2019; 123:9850-9856. [DOI: 10.1021/acs.jpca.9b08988] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Josefredo R. Pliego
- Departamento de Ciências Naturais, Universidade Federal de São João del-Rei, São João del-Rei, 36301-160 MG, Brazil
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