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Dae Yoon Chi - One of the best experts on this subject based on the ideXlab platform.
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hydrogen bond promoted nucleophilic fluorination concept mechanism and applications in positron emission tomography
Chemical Society Reviews, 2016Co-Authors: Jiwoong Lee, Maria Teresa Oliveira, Hyeong Bin Jang, Sungyul Lee, Dae Yoon Chi, Dong Wook Kim, Choong Eui SongAbstract:Due to the tremendous interest in carbon-fluorine bond-forming reactions, research efforts in this area have been dedicated to the development of facile processes to synthesize small fluorine-containing organic molecules. Among others, PET (Positron Emission Tomography) is one of the most important applications of fluorine chemistry. Recognizing the specific requirements of PET processes, some groups have focused on fluorination reactions using alkali metal Fluorides, particularly through SN2-type reactions. However, a common "misconception" about the role of protic solvents and hydrogen bonding interactions in this class of reactions has hampered the employment of these excellent promoters. Herein, we would like to review recent discoveries in this context, showing straightforward nucleophilic fluorination reactions using alkali metal Fluorides promoted by protic solvents. Simultaneous dual activation of reacting partners by intermolecular hydrogen bonding and the enhancement of the "effective Fluoride nucleophilicity", which is Nature's biocatalytic approach with the fluorinase enzyme, are the key to this unprecedentedly successful nucleophilic fluorination.
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facile nucleophilic fluorination reactions using tert alcohols as a reaction medium significantly enhanced reactivity of alkali metal Fluorides and improved selectivity
Journal of Organic Chemistry, 2008Co-Authors: Dong Wook Kim, Hwanjeong Jeong, Seok Tae Lim, Myunghee Sohn, John A Katzenellenbogen, Dae Yoon ChiAbstract:Although protic solvents are generally not preferred for nucleophilic displacement reactions because of their partial positive charge and hydrogen-bonding capacity that solvate the nucleophile and reduce its reactivity, we recently reported a remarkably beneficial effect of using tertiary alcohols as a reaction media for nucleophilic fluorination with alkali metal Fluorides, as well as fluorine-18 radiolabeling with [18F]Fluoride ion for the preparation of PET radiopharmaceuticals. In this work, we investigate further the influence of the tert-alcohol reaction medium for nucleophilic fluorination with alkali metal Fluorides by studying various interactions among tert-alcohols, the alkali metal Fluoride (CsF), and the sulfonyloxy substrate. Factors such as hydrogen bonding between CsF and the tert-alcohol solvent, the formation of a tert-alcohol solvated Fluoride, and hydrogen bonding between the sulfonate leaving group and the tert-alcohol appear to contribute to the dramatic increase in the rate of the nucleophilic fluorination reaction in the absence of any kind of catalyst. We found that fluorination of 1-(2-mesyloxyethyl)naphthalene (5) and N-5-bromopentanoyl-3,4-dimethoxyaniline (8) with Bu(4)N(+)F(-) in a tert-alcohol afforded the corresponding fluoro products in much higher yield than obtained by the conventional methods using dipolar aprotic solvents. The protic medium also suppresses formation of byproducts, such as alkenes, ethers, and cyclic adducts.
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a new class of sn2 reactions catalyzed by protic solvents facile fluorination for isotopic labeling of diagnostic molecules
Journal of the American Chemical Society, 2006Co-Authors: Dong Wook Kim, Sungyul Lee, Doosik Ahn, Hee Seup Kil, Sang Ju Lee, Jae Seung Kim, Jinsook Ryu, Dae Hyuk Moon, Dae Yoon ChiAbstract:Aprotic solvents are usually preferred for the SN2 reactions, because nucleophilicity and hence SN2 reactivity are severely retarded by the influence of the partial positive charge of protic solvents. In this work, we introduce a remarkable effect of using tertiary alcohols as a reaction medium for nucleophilic fluorination with alkali metal Fluorides. In this novel synthetic method, the nonpolar protic tert-alcohol enhances the nucleophilicity of the Fluoride ion dramatically in the absence of any kind of catalyst, greatly increasing the rate of the nucleophilic fluorination and reducing formation of byproducts (such as alkenes, alcohols, or ethers) compared with conventional methods using dipolar aprotic solvents. The great efficacy of this method is a particular advantage in labeling radiopharmaceuticals with [18F]fluorine (t1/2 = 110 min) for positron emission tomographic (PET) imaging, and it is illustrated by the synthesis of four [18F]Fluoride-radiolabeled molecular imaging probes[18F]FDG, [18F]FLT...
Maximilian Fichtner - One of the best experts on this subject based on the ideXlab platform.
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solid electrolytes for Fluoride ion batteries ionic conductivity in polycrystalline tysonite type Fluorides
ACS Applied Materials & Interfaces, 2014Co-Authors: Carine Rongeat, Anji M Reddy, Raiker Witter, Maximilian FichtnerAbstract:Batteries based on a Fluoride shuttle (Fluoride ion battery, FIB) can theoretically provide high energy densities and can thus be considered as an interesting alternative to Li-ion batteries. Large improvements are still needed regarding their actual performance, in particular for the ionic conductivity of the solid electrolyte. At the current state of the art, two types of Fluoride families can be considered for electrolyte applications: alkaline-earth Fluorides having a fluorite-type structure and rare-earth Fluorides having a tysonite-type structure. As regard to the latter, high ionic conductivities have been reported for doped LaF3 single crystals. However, polycrystalline materials would be easier to implement in a FIB due to practical reasons in the cell manufacturing. Hence, we have analyzed in detail the ionic conductivity of La1–yBayF3–y (0 ≤ y ≤ 0.15) solid solutions prepared by ball milling. The combination of DC and AC conductivity analyses provides a better understanding of the conduction me...
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nanostructured fluorite type Fluorides as electrolytes for Fluoride ion batteries
Journal of Physical Chemistry C, 2013Co-Authors: Carine Rongeat, Anji M Reddy, Raiker Witter, Maximilian FichtnerAbstract:Fluoride ion batteries (FIB) provide an interesting alternative to lithium ion batteries, in particular because of their larger theoretical energy densities. These batteries are based on a F anion shuttle between a metal Fluoride cathode and a metal anode. One critical component is the electrolyte that should provide fast anion conduction. So far, this is only possible in solid so-called superionic conductors, at elevated temperatures. Herein, we analyze in detail the ionic conductivity in barium Fluoride salts doped with lanthanum (Ba1–xLaxF2+x). Doping by trivalent cations leads to an increase of the quantity of point defects in the BaF2 crystal. These defects participate in the ionic motion and therefore improve the ionic conductivity. We demonstrate that further improvement of the conductivity is possible by using a nanostructured material providing additional conduction paths through the grain boundaries. Using electrochemical impedance spectroscopy and AC conductivity analysis, we show that the ioni...
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batteries based on Fluoride shuttle
Journal of Materials Chemistry, 2011Co-Authors: Anji M Reddy, Maximilian FichtnerAbstract:In search of new concepts to build batteries with high energy densities, electrochemical cells based on metal Fluorides may be promising. Herein, we report the demonstration of secondary battery cells based on Fluoride shuttle. In Fluoride ion batteries, Fluoride anion acts as charge transfer ion between a metal/metal Fluoride pair where it will react with metal or evolve from metal Fluoride depending on the flow of current.
Dong Wook Kim - One of the best experts on this subject based on the ideXlab platform.
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hydrogen bond promoted nucleophilic fluorination concept mechanism and applications in positron emission tomography
Chemical Society Reviews, 2016Co-Authors: Jiwoong Lee, Maria Teresa Oliveira, Hyeong Bin Jang, Sungyul Lee, Dae Yoon Chi, Dong Wook Kim, Choong Eui SongAbstract:Due to the tremendous interest in carbon-fluorine bond-forming reactions, research efforts in this area have been dedicated to the development of facile processes to synthesize small fluorine-containing organic molecules. Among others, PET (Positron Emission Tomography) is one of the most important applications of fluorine chemistry. Recognizing the specific requirements of PET processes, some groups have focused on fluorination reactions using alkali metal Fluorides, particularly through SN2-type reactions. However, a common "misconception" about the role of protic solvents and hydrogen bonding interactions in this class of reactions has hampered the employment of these excellent promoters. Herein, we would like to review recent discoveries in this context, showing straightforward nucleophilic fluorination reactions using alkali metal Fluorides promoted by protic solvents. Simultaneous dual activation of reacting partners by intermolecular hydrogen bonding and the enhancement of the "effective Fluoride nucleophilicity", which is Nature's biocatalytic approach with the fluorinase enzyme, are the key to this unprecedentedly successful nucleophilic fluorination.
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facile nucleophilic fluorination reactions using tert alcohols as a reaction medium significantly enhanced reactivity of alkali metal Fluorides and improved selectivity
Journal of Organic Chemistry, 2008Co-Authors: Dong Wook Kim, Hwanjeong Jeong, Seok Tae Lim, Myunghee Sohn, John A Katzenellenbogen, Dae Yoon ChiAbstract:Although protic solvents are generally not preferred for nucleophilic displacement reactions because of their partial positive charge and hydrogen-bonding capacity that solvate the nucleophile and reduce its reactivity, we recently reported a remarkably beneficial effect of using tertiary alcohols as a reaction media for nucleophilic fluorination with alkali metal Fluorides, as well as fluorine-18 radiolabeling with [18F]Fluoride ion for the preparation of PET radiopharmaceuticals. In this work, we investigate further the influence of the tert-alcohol reaction medium for nucleophilic fluorination with alkali metal Fluorides by studying various interactions among tert-alcohols, the alkali metal Fluoride (CsF), and the sulfonyloxy substrate. Factors such as hydrogen bonding between CsF and the tert-alcohol solvent, the formation of a tert-alcohol solvated Fluoride, and hydrogen bonding between the sulfonate leaving group and the tert-alcohol appear to contribute to the dramatic increase in the rate of the nucleophilic fluorination reaction in the absence of any kind of catalyst. We found that fluorination of 1-(2-mesyloxyethyl)naphthalene (5) and N-5-bromopentanoyl-3,4-dimethoxyaniline (8) with Bu(4)N(+)F(-) in a tert-alcohol afforded the corresponding fluoro products in much higher yield than obtained by the conventional methods using dipolar aprotic solvents. The protic medium also suppresses formation of byproducts, such as alkenes, ethers, and cyclic adducts.
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a new class of sn2 reactions catalyzed by protic solvents facile fluorination for isotopic labeling of diagnostic molecules
Journal of the American Chemical Society, 2006Co-Authors: Dong Wook Kim, Sungyul Lee, Doosik Ahn, Hee Seup Kil, Sang Ju Lee, Jae Seung Kim, Jinsook Ryu, Dae Hyuk Moon, Dae Yoon ChiAbstract:Aprotic solvents are usually preferred for the SN2 reactions, because nucleophilicity and hence SN2 reactivity are severely retarded by the influence of the partial positive charge of protic solvents. In this work, we introduce a remarkable effect of using tertiary alcohols as a reaction medium for nucleophilic fluorination with alkali metal Fluorides. In this novel synthetic method, the nonpolar protic tert-alcohol enhances the nucleophilicity of the Fluoride ion dramatically in the absence of any kind of catalyst, greatly increasing the rate of the nucleophilic fluorination and reducing formation of byproducts (such as alkenes, alcohols, or ethers) compared with conventional methods using dipolar aprotic solvents. The great efficacy of this method is a particular advantage in labeling radiopharmaceuticals with [18F]fluorine (t1/2 = 110 min) for positron emission tomographic (PET) imaging, and it is illustrated by the synthesis of four [18F]Fluoride-radiolabeled molecular imaging probes[18F]FDG, [18F]FLT...
Joerg Feldmann - One of the best experts on this subject based on the ideXlab platform.
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novel non target analysis of fluorine compounds using icpms ms and hplc icpms ms
Journal of Analytical Atomic Spectrometry, 2017Co-Authors: Laili N A Jamari, Frederik J Dohmann, Andrea Raab, Eva M Krupp, Joerg FeldmannAbstract:Measuring sub-ppm levels of fluorine (F) directly with a commercial ICPMS is not possible due to the high ionisation potential of F. Mixing of barium and fluorine solutions enabled a new approach in fluorine analysis through the formation of the polyatomic ion BaF+ using ICPMS/MS. Different parameters such as reaction gas flow rate, sampling position, nebuliser and makeup gas flow rate, waiting and acquisition time as well as RF power were optimized in order to obtain the highest possible sensitivities for 138Ba19F+, as these parameters were important for polyatomic ion formation, avoiding barium oxide and barium hydroxide ion interference and sensitive detection in MS/MS. A limit of detection (LOD) of 0.043 mg L−1 was achieved with a good recovery of Fluoride spiked in deionised water. For fluorine speciation analysis, coupling of anion exchange chromatography online with ICPMS/MS allowed separation and fluorine specific detection of Fluoride and fluoroacetate. The response was compound independent as expected for ICPMS. The LODs of Fluoride and fluoroacetate were 0.022 mg L−1 and 0.11 mg L−1, respectively. Both compounds were baseline separated and detected quantitatively, making this newly developed method a promising candidate for non-target fluorine speciation analysis in environmental samples.
Carine Rongeat - One of the best experts on this subject based on the ideXlab platform.
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solid electrolytes for Fluoride ion batteries ionic conductivity in polycrystalline tysonite type Fluorides
ACS Applied Materials & Interfaces, 2014Co-Authors: Carine Rongeat, Anji M Reddy, Raiker Witter, Maximilian FichtnerAbstract:Batteries based on a Fluoride shuttle (Fluoride ion battery, FIB) can theoretically provide high energy densities and can thus be considered as an interesting alternative to Li-ion batteries. Large improvements are still needed regarding their actual performance, in particular for the ionic conductivity of the solid electrolyte. At the current state of the art, two types of Fluoride families can be considered for electrolyte applications: alkaline-earth Fluorides having a fluorite-type structure and rare-earth Fluorides having a tysonite-type structure. As regard to the latter, high ionic conductivities have been reported for doped LaF3 single crystals. However, polycrystalline materials would be easier to implement in a FIB due to practical reasons in the cell manufacturing. Hence, we have analyzed in detail the ionic conductivity of La1–yBayF3–y (0 ≤ y ≤ 0.15) solid solutions prepared by ball milling. The combination of DC and AC conductivity analyses provides a better understanding of the conduction me...
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nanostructured fluorite type Fluorides as electrolytes for Fluoride ion batteries
Journal of Physical Chemistry C, 2013Co-Authors: Carine Rongeat, Anji M Reddy, Raiker Witter, Maximilian FichtnerAbstract:Fluoride ion batteries (FIB) provide an interesting alternative to lithium ion batteries, in particular because of their larger theoretical energy densities. These batteries are based on a F anion shuttle between a metal Fluoride cathode and a metal anode. One critical component is the electrolyte that should provide fast anion conduction. So far, this is only possible in solid so-called superionic conductors, at elevated temperatures. Herein, we analyze in detail the ionic conductivity in barium Fluoride salts doped with lanthanum (Ba1–xLaxF2+x). Doping by trivalent cations leads to an increase of the quantity of point defects in the BaF2 crystal. These defects participate in the ionic motion and therefore improve the ionic conductivity. We demonstrate that further improvement of the conductivity is possible by using a nanostructured material providing additional conduction paths through the grain boundaries. Using electrochemical impedance spectroscopy and AC conductivity analysis, we show that the ioni...
