Control of reactivity and selectivity of guanidinyliodonium salts toward 18F-Labeling by monitoring of protecting groups: Experiment and theory

Jang, Keum-Seong; Lee, Sung-Sik; Oh, Young Ho; Lee, Sangeun; Kim, Sang Eun; Kim, Dong Wook; Lee, Byung Chul; Raffel, David M.

doi:10.1016/j.jfluchem.2019.109387

Cited by 7 publications

(3 citation statements)

References 70 publications

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“…Diaryliodonium salts appear as fairly appealing electrophilic arylating reagents as well as precursors for positron emission tomography (PET) [39,40]. They are powerful intermediates for the synthesis of a broad range of radiofluorinated synthons and clinically relevant PET tracers [41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56]. Since the pioneering works on the palladium-and copper-catalyzed arylation of sp2 C-H indoles reported respectively by Sanford [57] and Gaunt groups [58], Nand C-arylation involving diaryliodonium salts offer a highly complementary strategy for the synthesis and derivatization of heteroarenes (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

Diaryliodoniums Salts as Coupling Partners for Transition-Metal Catalyzed C- and N-Arylation of Heteroarenes

2020

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Owing to the pioneering works performed on the metal-catalyzed sp2 C–H arylation of indole and pyrrole by Sanford and Gaunt, N– and C-arylation involving diaryliodonium salts offers an attractive complementary strategy for the late-stage diversification of heteroarenes. The main feature of this expanding methodology is the selective incorporation of structural diversity into complex molecules which usually have several C–H bonds and/or N–H bonds with high tolerance to functional groups and under mild conditions. This review summarizes the main recent achievements reported in transition-metal-catalyzed N– and/or C–H arylation of heteroarenes using acyclic diaryliodonium salts as coupling partners.

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Section: Introductionmentioning

confidence: 99%

Diaryliodoniums Salts as Coupling Partners for Transition-Metal Catalyzed C- and N-Arylation of Heteroarenes

2020

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“…One such example is the aromatic 18 F-labeling of guanidine-containing radiopharmaceutical [60][61][62][63][64][65][66][67][68][69][70] that was synthesized by nucleophilic fluorination of diaryliodonium salts. Jang and coworkers [71] found that the positions of -Boc protection profoundly affected the efficiency of 18 F-labeling: The fully protected N,N',N¨,N¨-tetrakis-Boc guanidine group (1b in Scheme 4) exhibited remarkably enhanced reactivity (yield = 39% in 5 min) and improved selectivity in contrast to N,N'-bis-Boc protected guanidine (1a, yield ≈ 0) in the absence of hydrogen bonding with fluoride ion (Scheme 4). What is the origin of these very intriguing observations?…”

Section: Methodsmentioning

confidence: 99%

Harnessing Ionic Interactions and Hydrogen Bonding for Nucleophilic Fluorination

Choi

Park

et al. 2020

Molecules

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We review recent works for nucleophilic fluorination of organic compounds in which the Coulombic interactions between ionic species and/or hydrogen bonding affect the outcome of the reaction. SN2 fluorination of aliphatic compounds promoted by ionic liquids is first discussed, focusing on the mechanistic features for reaction using alkali metal fluorides. The influence of the interplay of ionic liquid cation, anion, nucleophile and counter-cation is treated in detail. The role of ionic liquid as bifunctional (both electrophilic and nucleophilic) activator is envisaged. We also review the SNAr fluorination of diaryliodonium salts from the same perspective. Nucleophilic fluorination of guanidine-containing of diaryliodonium salts, which are capable of forming hydrogen bonds with the nucleophile, is exemplified as an excellent case where ionic interactions and hydrogen bonding significantly affect the efficiency of reaction. The origin of experimental observation for the strong dependence of fluorination yields on the positions of -Boc protection is understood in terms of the location of the nucleophile with respect to the reaction center, being either close to far from it. Recent advances in the synthesis of [18F]F-dopa are also cited in relation to SNAr fluorination of diaryliodonium salts. Discussions are made with a focus on tailor-making promoters and solvent engineering based on ionic interactions and hydrogen bonding.

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“…The 18 F-fluorination [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 ] of organic compounds is gaining considerable importance for synthesizing chemicals that can be employed as radiotracers for the diagnosis of various diseases [ 21 , 22 , 23 ] by the highly sensitive imaging technique of positron emission tomography (PET) [ 24 , 25 ]. Electrophilic substitution reactions [ 26 , 27 , 28 ] using the carrier added [ 18 F]F 2 gas were the earlier method for this purpose, but this approach usually suffers from poor radiochemical yields (RCYs) and from the difficulty of handling the [ 18 F]F 2 gas.…”

Section: Introductionmentioning

confidence: 99%

Nucleophilic Radiofluorination Using Tri-tert-Butanol Ammonium as a Bifunctional Organocatalyst: Mechanism and Energetics

Shinde

Lee

2022

Molecules

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We present a quantum chemical analysis of the 18F-fluorination of 1,3-ditosylpropane, promoted by a quaternary ammonium salt (tri-(tert-butanol)-methylammonium iodide (TBMA-I) with moderate to good radiochemical yields (RCYs), experimentally observed by Shinde et al. We obtained the mechanism of the SN2 process, focusing on the role of the –OH functional groups facilitating the reactions. We found that the counter-cation TBMA+ acts as a bifunctional promoter: the –OH groups function as a bidentate ‘anchor’ bridging the nucleophile [18F]F− and the –OTs leaving group or the third –OH. These electrostatic interactions cooperate for the formation of the transition states of a very compact configuration for facile SN2 18F-fluorination.

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Control of reactivity and selectivity of guanidinyliodonium salts toward 18F-Labeling by monitoring of protecting groups: Experiment and theory

Cited by 7 publications

References 70 publications

Diaryliodoniums Salts as Coupling Partners for Transition-Metal Catalyzed C- and N-Arylation of Heteroarenes

Diaryliodoniums Salts as Coupling Partners for Transition-Metal Catalyzed C- and N-Arylation of Heteroarenes

Harnessing Ionic Interactions and Hydrogen Bonding for Nucleophilic Fluorination

Nucleophilic Radiofluorination Using Tri-tert-Butanol Ammonium as a Bifunctional Organocatalyst: Mechanism and Energetics

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