Nucleophilic substitution versus electron transfer: 1. On the mechanism of electrophilic fluorinations

Differding, Edmond; Rüegg, Gabriela M.

doi:10.1016/s0040-4039(00)79383-x

Cited by 79 publications

(44 citation statements)

References 20 publications

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“…In metalation-fluorination reactions, an electron transfer (ET) mechanism has been suggested as a competing path to the S N 2 fluorination 22. We have shown in the past that metalation-fluorination of 1,3-benzothiazol-2-yl arylmethyl sulfones proceeded well under heterogeneous conditions (formation of carbanion in toluene, followed by addition of solid NFSI).…”

Section: Resultsmentioning

confidence: 99%

Fluorinated 1-Phenyl-1H-tetrazol-5-yl Sulfone Derivatives as General Reagents for Fluoroalkylidene Synthesis

Ghosh

Zajc

2009

J. Org. Chem.

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Julia-Kocienski olefination reagents 1-fluoropropyl, (cyclopropyl)fluoromethyl, 1-fluoro-2-methyl-2-propenyl and 1-fluoro-5-hexenyl 1-phenyl-1H-tetrazol-5-yl (PT) sulfones were prepared by metalation followed by electrophilic fluorination. Although metalation-fluorination of n-propyl, 5-hexenyl and (cyclopropyl)methyl PT-sulfones proceeded under homogeneous conditions, fluorination of 2-methyl-2-propenyl PT-sulfone required heterogeneous fluorination conditions. Condensation reactions of fluoro PT-sulfones with aldehydes resulted in fluoroalkylidenes in high yields. Screening of olefination conditions showed that stereoselectivity depended on reagent and carbonyl structure and can in many cases be tuned either towards E-or Z-selectivity. For example, LHMDS-mediated condensations of 1-fluoropropyl PT-sulfone in the presence of MgBr 2 ·OEt 2 were Z-selective with electron-rich aromatic aldehydes, a hindered aromatic aldehyde and cinnamaldehyde. Low temperature KHMDS-mediated condensations were E-selective with electron-rich and electron-deficient aromatic aldehydes and Z-selective with n-octanal. Dialkyl, aryl alkyl and diaryl ketones reacted as well to give fluoro olefin products in 71-99% yields.

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Section: Resultsmentioning

confidence: 99%

Fluorinated 1-Phenyl-1H-tetrazol-5-yl Sulfone Derivatives as General Reagents for Fluoroalkylidene Synthesis

Ghosh

Zajc

2009

J. Org. Chem.

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“…As known for reactions of electrophilic NF-agents with olefins there are two possible mechanistic pathways: single-electron transfer (SET) [32,35,36] or nucleophilic S N 2 substitution [37,38] but both mechanisms lead to the same a fluorinated carbocation which virtually determines the composition of the reaction products (Scheme 2).…”

Section: Fluorination Of Norbornenecarboxylic Acids and Their Methyl mentioning

confidence: 99%

Fluorolactonization of norbornenecarboxylic acids and their methyl esters with F-TEDA-BF4 and XeF2

Lourie

Serguchev

Shevchenko

et al. 2006

Journal of Fluorine Chemistry

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“…Differding and coworkers were the first to use radical clocks to monitor the reaction for the presence of intermediate radicals. [73,74] Their experiment was based on the following logic: If the potassium enolate 25 a were to react in an SET process, the resulting radical 25 b would undergo cyclization to the radical 25 c (Scheme 29). The recombination of 25 c and atomic fluorine would produce some amount of 26 c and 26 d, thus proving the existence of radicals in the reaction.…”

Section: Mechanism Of Fluorination With Selectfluor: Electron Transfementioning

confidence: 99%

“…[79] Selectfluor and the other compounds of this general class are the only electrophilic fluorination reagents for which no clear evidence has been found for the intermediacy of radical Table 10: Yields of products (in %) from reactions of fluorinating reagents with 25 a (see Scheme 29). [73,74] [ 10] intermediates. The DesMarteau reagent (2, Scheme 2) is inhibited by p-dinitrobenzene, [12] an efficient electron-transfer quencher, and N-fluoropyridinium reagents display CT bands indicative of SET, as described previously.…”

Section: Electrophilic Fluorinationmentioning

confidence: 99%

Selectfluor: Mechanistic Insight and Applications

et al. 2004

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The replacement of hydrogen atoms with fluorine substituents in organic substrates is of great interest in synthetic chemistry because of the strong electronegativity of fluorine and relatively small steric footprint of fluorine atoms. Many sources of nucleophilic fluorine are available for the derivatization of organic molecules under acidic, basic, and neutral conditions. However, electrophilic fluorination has historically required molecular fluorine, whose notorious toxicity and explosive tendencies limit its application in research. The necessity for an electrophilic fluorination reagent that is safe, stable, highly reactive, and amenable to industrial production as an alternative to very hazardous molecular fluorine was the inspiration for the discovery of selectfluor. This reagent is not only one of the most reactive electrophilic fluorinating reagents available, but it is also safe, nontoxic, and easy to handle. In this Review we document the many applications of selectfluor and discuss possible mechanistic pathways for its reaction.

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Nucleophilic substitution versus electron transfer: 1. On the mechanism of electrophilic fluorinations

Cited by 79 publications

References 20 publications

Fluorinated 1-Phenyl-1H-tetrazol-5-yl Sulfone Derivatives as General Reagents for Fluoroalkylidene Synthesis

Fluorinated 1-Phenyl-1H-tetrazol-5-yl Sulfone Derivatives as General Reagents for Fluoroalkylidene Synthesis

Fluorolactonization of norbornenecarboxylic acids and their methyl esters with F-TEDA-BF4 and XeF2

Selectfluor: Mechanistic Insight and Applications

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