Visible Light‐Mediated Trifluoromethylation of Fluorinated Alkenes via C−F Bond Cleavage

Wu, Liu-Hai; Cheng, Jun‐Kee; Shen, Liang; Shen, Zhi‐Liang; Loh, Teck‐Peng

doi:10.1002/adsc.201800740

Cited by 93 publications

(39 citation statements)

References 87 publications

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“…Taking advantage of these benefits, the reaction was further applied to enrich the DNA-encoded library via the photocatalytic defluorinative coupling of DNA-tagged α-CF3 styrenes and alkyl radical precursors in the open air and aqueous media (Scheme 23b) [65]. The robustness of this visible-light-mediated radical-polar crossover additionelimination protocol for the C-F bond cleavage of α-trifluoromethyl alkenes was further demonstrated by the use of alkylboronic acids (Scheme 24a) [66], CF3SO2Na (Scheme 24b) [67], and glyoxylic acid acetals (Scheme 24c) [68] as the radical precursors. The common feature of the radical sources is their low redox potential to be SET oxidized by excited photocatalyst, producing a one-electron-reduced form of photocatalyst (PC − ) to switch the subsequent α-CF3 carbon radicals to carbon ions.…”

Section: Trifluoromethyl Alkenesmentioning

confidence: 99%

Recent Advances in C-F Bond Cleavage Enabled by Visible Light Photoredox Catalysis

Zhou

2021

Molecules

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The creation of new bonds via C-F bond cleavage of readily available per- or oligofluorinated compounds has received growing interest. Using such a strategy, a myriad of valuable partially fluorinated products can be prepared, which otherwise are difficult to make by the conventional C-F bond formation methods. Visible light photoredox catalysis has been proven as an important and powerful tool for defluorinative reactions due to its mild, easy to handle, and environmentally benign characteristics. Compared to the classical C-F activation that proceeds via two-electron processes, radicals are the key intermediates using visible light photoredox catalysis, providing new modes for the cleavage of C-F bonds. In this review, a summary of the visible light-promoted C-F bond cleavage since 2018 was presented. The contents were classified by the fluorosubstrates, including polyfluorinated arenes, gem-difluoroalkenes, trifluoromethyl arenes, and trifluoromethyl alkenes. An emphasis is placed on the discussion of the mechanisms and limitations of these reactions. Finally, my personal perspective on the future development of this rapidly emerging field was provided.

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Section: Trifluoromethyl Alkenesmentioning

confidence: 99%

Recent Advances in C-F Bond Cleavage Enabled by Visible Light Photoredox Catalysis

Zhou

2021

Molecules

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“…This reaction exploited CF 3 SO 2 Na as an efficient source of * CF 3 and Ir III as a photocatalyst for generating CF 3 -containing multifluorinated molecules in moderate to good yields with high stereoselectivity (Scheme 74). [59] Irradiation by visible light sensitized Ir III to its excited state *Ir III , which subsequently oxidized NaSO 2 CF 3 via a SET and generated Ir III -mediated visible-light-catalyzed defluorinative crosscoupling of gem-difluoroalkenes with different types of thiols, can regioseletively generate various monofluoroalkenes (Scheme 76). [60] Of note, reactions of monosubstituted gemdifluoroalkenes worked better in toluene, whereas disubstituted gem-difluoroalkenes, performed better using acetonitrile as a solvent.…”

Section: Oxidative Photocatalytic Reactions Of Gem-difluoroalkenesmentioning

confidence: 99%

“…This reaction exploited CF 3 SO 2 Na as an efficient source of . CF 3 and Ir III as a photocatalyst for generating CF 3 ‐containing multifluorinated molecules in moderate to good yields with high stereoselectivity (Scheme ) …”

Section: Generation Of Trifluoromethanesmentioning

confidence: 99%

Recent Advances in Transition Metal‐Catalyzed Functionalization of gem‐Difluoroalkenes

Koley

Altman

2020

Israel Journal of Chemistry

131

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gem-Difluorinated alkenes are readily accessible building blocks that can undergo functionalization to provide a broad spectrum of fluorinated and non-fluorinated products. Herein, we review recent (since 2017) transition metalcatalyzed transformations of these specialized alkenes and summarize general reactivity patterns of these reactions. Many transition metal-catalyzed reactions undergo net CÀ F bond functionalization reactions to deliver monofluorinated products. These reactions typically proceed through β-fluoroalkylmetal intermediates that readily eliminate a βfluoride to deliver monofluoroalkene products. A second series of reactions exploit coinage metal fluorides to add F À to the gem-difluorinated alkene, and further functionalization delivers trifluoromethyl-containing products. In stark contrast, few transition metal-catalyzed reactions proceed in net "fluorine-retentive processes" to deliver difluoromethylenebased products. Reactions Proceeding via β-Fluoride Eliminationgem-Difluoroalkenes react with a variety of transition metalbased catalyst systems (e. g. Cu, Co, Mn, Pd, Ni, Ru, Rh) in net CÀ F functionalization reactions. These reactions typically proceed through a β-fluoroalkylmetal intermediate that readily undergoes β-fluoride elimination to form a new alkene based product (Scheme 1). At first, reaction of a substrate-ligated complex (1) to the gem-difluoroalkene 2, proceeds through a four-membered transition state 3 to generate the intermediate 4. This process involves the matching of the anionic ligand (Y) with the cationic α,α-difluorinated position of the alkene, which generates an intermediate metalalkyl bearnig two βfluoride atoms. Subsequent β-fluoride elimination generates [a] S.Scheme 3. Plausible mechanism for defluoroborylation of aliphatic gem-difluoroalkenes. Scheme 4. CÀ F Bond borylation of gem-difluoroalkenes. Scheme 5. Copper-catalyzed trans-selective monodefluoroborylation of various gem-difluoroalkenes. Scheme 6. CÀ F Bond borylation of gem-difluoroalkenes. Scheme 7. Copper-catalyzed tunable multi-borylation reactions of gem-difluoroalkenes. In parentheses the ratio of 22, 23 and 24 is reported. Scheme 8. Stereoselective defluorinative borylation and silylation of gem-difluoroalkenes. Scheme 9. a) Synthesis of fluorinated vinylsilanes from gem-difluoro/ polyfluoroalkenes. b) Cross-coupling reaction of 29 b and iodobenzene. Scheme 10. Nickel-catalyzed fluoroalkenylation of unactivated alkylbromides. rr = The regioisomeric ratio of the benzylic fluoroÀ alkenylation product to the other regioisomers. DMA = N,N-Dimethylacetamide. Scheme 14. Iron-catalyzed defluorinative cross-coupling of donor alkenes with gem-difluoroalkenes. Dibm = diisobutyrylmethane. Scheme 15. Nickel-catalyzed reductive aryl monofluoroalkenylation of alkenes. Scheme 16. Plausible mechanism for reductive aryl monofluoroalkenylation of gem-difluoroalkenes. Scheme 17. Nickel-catalyzed hydroalkenylation of alkynes through oxidative cyclization and β-fluoride elimination. Scheme 28. Ruthenium-catalyzed fluoroal...

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“…In this regard, gem ‐difluoroalkene represents a useful reaction component as that is easily available from aldehydes, ketones, alkyl halides, trifluoromethyl allyl/propargyl/alkenyl carbonates and diazo compounds. Such fluorinated alkene has been employed as a versatile building block, with which a large variety of mono‐fluoroalkenes featuring synthetically important functionalities, including aryl, alkyl, alkynyl, cyano, trifluoromethyl, as well as heteroatoms, have been successfully prepared through transition‐metal‐catalyzed or radical‐engaged functionalization of the classically considered inert C—F bond. Among the established protocols, C—H activation coupled C—F bond functionalization is of particular interest because of the outstanding efficiency and broad substrate scope.…”

Section: Background and Originality Contentmentioning

confidence: 99%

Rhodium‐Catalyzed Defluorinative Vinylation of gem‐Difluoroalkenes for the Synthesis of 2‐Fluoro‐1,3‐dienes

et al. 2019

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of main observation and conclusion Herein, we present a strategy for the formation of 2-fluoro-1,3-diene derivatives via rhodium-catalyzed direct C(sp 2 )-C(sp 2 ) cross-coupling of gem-difluoroalkenes and acrylamides. By merging Rh(III)-catalyzed C(sp 2 )-H bond activation and nucleophilic addition/F-elimination of gem-difluoroalkene, an efficient defluorinative vinylation reaction is uncovered, which leads to the generation of 2-fluoro-1,3-dienes in moderate to good yields with excellent stereoselectivity under mild conditions. Preliminary mechanistic study suggests unique effects of fluorine substituents which allow the reactivity profile not observed with the congeners bearing heavier halides.

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Visible Light‐Mediated Trifluoromethylation of Fluorinated Alkenes via C−F Bond Cleavage

Cited by 93 publications

References 87 publications

Recent Advances in C-F Bond Cleavage Enabled by Visible Light Photoredox Catalysis

Recent Advances in C-F Bond Cleavage Enabled by Visible Light Photoredox Catalysis

Recent Advances in Transition Metal‐Catalyzed Functionalization of gem‐Difluoroalkenes

Rhodium‐Catalyzed Defluorinative Vinylation of gem‐Difluoroalkenes for the Synthesis of 2‐Fluoro‐1,3‐dienes

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