- Dehydroxylative Fluorination of Tertiary Alcohols
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A large number of fluorination methods have been developed, but the construction of a tertiary C-F bond remains challenging. Herein, we describe an efficient dehydroxylative fluorination of tertiary alcohols with Selectfluor via the activation of a hydroxyl group by a Ph2PCH2CH2PPh2/ICH2CH2I system. Although the reagents appear to be not compatible (Selectfluor with the phosphine and I- generated in situ), the reactions occur rapidly to give the desired products in moderate to high yields. This work may present a new discovery in fluorination of alcohols since the reported methods are mainly limited to primary and secondary alcohols.
- Zhang, Wei,Gu, Yu-Cheng,Lin, Jin-Hong,Xiao, Ji-Chang
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supporting information
p. 6642 - 6646
(2020/09/02)
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- Predictable site-selective radical fluorination of tertiary ethers
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In this communication, we disclose the first example of metal-free and site-selective radical fluorination of readily available tertiary alkyl ethers, enabled by synergistic photocatalysis and organocatalysis. This catalytic combination allows for exclusi
- Ma, Junyang,Xu, Wentao,Xie, Jin
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p. 187 - 191
(2019/11/21)
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- Nickel-Catalyzed Hydrofluorination of Unactivated Alkenes through a HAT Pathway
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We report the hydrofluorination of unactivated alkenes using N-fluorobenzenesulfonimide as a fluorination reagent. The reaction produces exclusively Markovnikov hydrofluorination products under mild conditions. It is not affected by air or moisture and us
- Song, Peihong,Zhu, Shaolin
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p. 13165 - 13170
(2020/11/17)
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- Nucleophilic (Radio)Fluorination of Redox-Active Esters via Radical-Polar Crossover Enabled by Photoredox Catalysis
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We report a redox-neutral method for nucleophilic fluorination of N-hydroxyphthalimide esters using an Ir photocatalyst under visible light irradiation. The method provides access to a broad range of aliphatic fluorides, including primary, secondary, and tertiary benzylic fluorides as well as unactivated tertiary fluorides, that are typically inaccessible by nucleophilic fluorination due to competing elimination. In addition, we show that the decarboxylative fluorination conditions are readily adapted to radiofluorination with [18F]KF. We propose that the reactions proceed by two electron transfers between the Ir catalyst and redox-active ester substrate to afford a carbocation intermediate that undergoes subsequent trapping by fluoride. Examples of trapping with O- and C-centered nucleophiles and deoxyfluorination via N-hydroxyphthalimidoyl oxalates are also presented, suggesting that this approach may offer a general blueprint for affecting redox-neutral SN1 substitutions under mild conditions.
- Webb, Eric W.,Park, John B.,Cole, Erin L.,Donnelly, David J.,Bonacorsi, Samuel J.,Ewing, William R.,Doyle, Abigail G.
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p. 9493 - 9500
(2020/05/18)
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- Light-Mediated Formal Radical Deoxyfluorination of Tertiary Alcohols through Selective Single-Electron Oxidation with TEDA2+.
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The synthesis of tertiary alkyl fluorides through a formal radical deoxyfluorination process is described herein. This light-mediated, catalyst-free methodology is fast and broadly applicable allowing for the preparation of C?F bonds from (hetero)benzylic, propargylic, and non-activated tertiary alcohol derivatives. Preliminary mechanistic studies support that the key step of the reaction is the single-electron oxidation of cesium oxalates—which are readily available from the corresponding tertiary alcohols—with in situ generated TEDA2+. (TEDA: N-(chloromethyl)triethylenediamine), a radical cation derived from Selectfluor.
- Aguilar Troyano, Francisco José,Ballaschk, Frederic,Jaschinski, Marcel,?zkaya, Yasemin,Gómez-Suárez, Adrián
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supporting information
p. 14054 - 14058
(2019/11/11)
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- Direct Hydrofluorination of Methallyl Alkenes Using a Methanesulfonic Acid/Triethylamine Trihydrofluoride Combination
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The use of a methanesulfonic acid/triethylamine trihydrofluoride combination for the direct hydrofluorination of methallyl-containing substrates is reported. Under those metal-free conditions that use readily available, cheap, and easy to handle reagents,
- Bertrand, Xavier,Paquin, Jean-Fran?ois
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p. 9759 - 9762
(2019/11/28)
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- Photoredox-catalyzed deoxyfluorination of activated alcohols with Selectfluor
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Herein we disclose a deoxyfluorination of alcohols with an electrophilic fluorine source via visible-light photoredox catalysis. This radical-mediated C–F coupling is capable of fluorinating secondary and tertiary alcohols efficiently, complementing previously reported nucleophilic deoxyfluorination protocols.
- González-Esguevillas, María,Miró, Javier,Jeffrey, Jenna L.,MacMillan, David W.C.
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supporting information
p. 4222 - 4227
(2019/06/13)
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- Ligand-Promoted Iron(III)-Catalyzed Hydrofluorination of Alkenes
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An iron-catalyzed hydrofluorination of unactivated alkenes has been developed. The use of a multidentate ligand and the fluorination reagent N-fluorobenzenesulfonimide (NFSI) proved to be critical for this reaction, which afforded various fluorinated comp
- Xie, Yongtao,Sun, Peng-Wei,Li, Yuxin,Wang, Siwei,Ye, Mengchun,Li, Zhengming
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supporting information
p. 7097 - 7101
(2019/04/17)
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- Nucleophilic Substitution of Aliphatic Fluorides via Pseudohalide Intermediates
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A method for aliphatic fluoride functionalization with a variety of nucleophiles has been reported. Carbon–fluoride bond cleavage is thermodynamically driven by the use of silylated pseudohalides TMS-OMs or TMS-NTf2, resulting in the formation of TMS-F and a trapped aliphatic pseudohalide intermediate. The rate of fluoride/pseudohalide exchange and the stability of this intermediate are such that little rearrangement is observed for terminal fluoride positions in linear aliphatic fluorides. The ability to convert organofluoride positions into pseudohalide groups allows facile nucleophilic attack by a wide range of nucleophiles. The late introduction of the nucleophiles also allows for a wide range of functional-group tolerance in the coupling partners. Selective alkyl fluoride mesylation is observed in the presence of other alkyl halides, allowing for orthogonal synthetic strategies.
- Jaiswal, Amit K.,Prasad, Pragati K.,Young, Rowan D.
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supporting information
p. 6290 - 6294
(2019/04/26)
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- Selective Radical Fluorination of Tertiary Alkyl Halides at Room Temperature
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Direct fluorination of tertiary alkyl bromides and iodides with Selectfluor is described. The halogen-exchange fluorination proceeds efficiently in acetonitrile at room temperature under metal-free conditions and exhibits a wide range of functional group compatibility. Furthermore, the reactions are highly selective in that alkyl chlorides and primary and secondary alkyl bromides remain intact. A radical mechanism is proposed for this selective fluorination.
- Chen, He,Liu, Zhonglin,Lv, Ying,Tan, Xinqiang,Shen, Haigen,Yu, Hai-Zhu,Li, Chaozhong
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supporting information
p. 15411 - 15415
(2017/11/10)
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- Catalytic B(C6F5)3[rad]H2O-promoted defluorinative functionalization of tertiary aliphatic fluorides
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A B(C6F5)3[rad]H2O-catalyzed defluorinative functionalization of tertiary aliphatic fluorides is described that proceeds under benign reaction conditions. The synthetic utility of the method is exemplified throu
- Dryzhakov, Marian,Richmond, Edward,Li, Guang,Moran, Joseph
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- Tetramethylfluoroformamidinium hexafluorophosphate (TFFH) as a mild deoxofluorination reagent
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The solid, air-stable peptide coupling reagent TFFH (tetramethylfluoroformamidinium hexafluorophosphate) was found to activate a variety of alcohols towards deoxofluorination. These conditions are compatible with carbonyl functional groups thus offering interesting possibilities for the application to sensitive molecules. Georg Thieme Verlag Stuttgart · New York.
- Bellavance, Gabriel,Dubé, Pascal,Nguyen, Bao
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experimental part
p. 569 - 572
(2012/04/17)
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- Fluorine transfer to alkyl radicals
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The development of new synthetic technologies for the selective fluorination of organic compounds has increased with the escalating importance of fluorine-containing pharmaceuticals. Traditional methods potentially applicable to drug synthesis rely on the use of ionic forms of fluorine (F - or F+). Radical methods, while potentially attractive as a complementary approach, are hindered by a paucity of safe sources of atomic fluorine (F?). A new approach to alkyl fluorination has been developed that utilizes the reagent N-fluorobenzenesulfonimide as a fluorine transfer agent to alkyl radicals. This approach is successful for a broad range of alkyl radicals, including primary, secondary, tertiary, benzylic, and heteroatom-stabilized radicals. Furthermore, calculations reveal that fluorine-containing ionic reagents are likely candidates for further expansion of this approach to polar reaction media. The use of these reagents in alkyl radical fluorination has the potential to enable powerful new transformations that otherwise would take multiple synthetic steps.
- Rueda-Becerril, Montserrat,Chatalova Sazepin, Claire,Leung, Joe C. T.,Okbinoglu, Tulin,Kennepohl, Pierre,Paquin, Jean-Francois,Sammis, Glenn M.
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supporting information; experimental part
p. 4026 - 4029
(2012/04/10)
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- Boron trifluoride-mediated alkylation of diphenylphosphine with tert-alkyl fluoride
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(Chemical Equation Presented) Treatment of tertiary alkyl fluoride with diphenylphosphine in the presence of a stoichiometric amount of boron trifluoride etherate yields the corresponding tert-alkyldiphenylphosphine despite the coexistence of the strong L
- Hirano, Koji,Yorimitsu, Hideki,Oshima, Koichiro
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p. 4873 - 4875
(2007/10/03)
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- Organoaluminum-catalyzed new alkylation of tert-alkyl fluorides: Synthetic utility of Al-F interaction
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tert-Alkyl fluorides have been revisited as promising alkylation agents based on the activation of fluorine as a leaving group by organoaluminums through the eminent AI-F interaction. Trialkylaluminums were found to be excellent catalysts as well as alkylation agents.
- Ooi, Takashi,Uraguchi, Daisuke,Kagoshima, Naoko,Maruoka, Keiji
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p. 5679 - 5682
(2007/10/03)
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