1977-87-3Relevant academic research and scientific papers
Selective Electrochemical Formyl Hydrogen-Exchange Fluorination of Aliphatic Aldehydes to Prepare Acyl Fluorides Using HF-Base Solutions
Yoneda, Norihiko,Chen, Sheng-Qi,Hatakeyama, Tsuyoshi,Hara, Syoji,Fukuhara, Tsuyoshi
, p. 849 - 850 (1994)
The selective displacement of formyl hydrogen to fluorine in aliphatic aldehydes was successfully carried out electrochemically to give acyl fluorides in base-nHF (base: pyridine or Et3N, n=3-6) electrolyte solution with or without solvents such as acetonitrile and sulfolane.
A new method for making acyl fluorides using BrF3
Cohen, Or,Sasson, Revital,Rozen, Shlomo
, p. 433 - 436 (2006)
While many carboxylic acids could be converted directly to acyl fluorides by using BrF3, the reaction with acyl chlorides was found to be of a more general nature and yields better results. Surprisingly, reacting t-butyl esters with bromine trifluoride also resulted in acyl fluorides in reasonable yields. The reactions were completed in a few seconds at 0°C.
Metal-free approach for hindered amide-bond formation with hypervalent iodine(iii) reagents: application to hindered peptide synthesis
Lee, Hyo-Jun,Huang, Xiao,Sakaki, Shigeyoshi,Maruoka, Keiji
, p. 848 - 855 (2021/02/09)
A new bio-inspired approach is reported for amide and peptide synthesis using α-amino esters that possess a potential activating group (PAG) at the ester residue. To activate the ester functionality under mild metal-free conditions, we exploited the facile dearomatization of phenols with hypervalent iodine(iii) reagents. Using a pyridine-hydrogen fluoride complex, highly reactive acyl fluoride intermediates can be successfully generated, thereby allowing for the smooth formation of sterically hindered amides and peptides from bulky amines and α-amino esters, respectively.
Radical-Mediated Activation of Esters with a Copper/Selectfluor System: Synthesis of Bulky Amides and Peptides
Matsumoto, Akira,Wang, Zhe,Maruoka, Keiji
, p. 5401 - 5411 (2021/04/12)
Herein, we describe a new approach for the activation of esters via a radical-mediated process enabled by a copper/Selectfluor system. A variety of para-methoxybenzyl esters derived from bulky carboxylic acids and amino acids can be easily converted into the corresponding acyl fluorides, directly used in the one-pot synthesis of amides and peptides. As a proof of concept, this method was applied to the iterative formation of sterically hindered amide bonds.
Gram-Scale Preparation of Acyl Fluorides and Their Reactions with Hindered Nucleophiles
Barbasiewicz, Micha?,Tryniszewski, Micha?
, (2021/11/30)
A series of acyl fluorides was synthesized at 100 mmol scale using phase-transfer-catalyzed halogen exchange between acyl chlorides and aqueous bifluoride solution. The convenient procedure consists of vigorous stirring of the biphasic mixture at room temperature, followed by extraction and distillation. Isolated acyl fluorides (usually 7-20 g) display excellent purity and can be transformed into sterically hindered amides and esters when treated with lithium amide bases and alkoxides under mild conditions.
N-Hydroxybenzimidazole as a structurally modifiable platform forN-oxyl radicals for direct C-H functionalization reactions
Hatanaka, Miho,Jiang, Julong,Maruoka, Keiji,Matsumoto, Akira,Sakamoto, Ryu,Sakurai, Shunya,Tsuzuki, Saori,Yoshii, Tomomi
, p. 5772 - 5778 (2020/06/22)
Methods for direct functionalization of C-H bonds mediated byN-oxyl radicals constitute a powerful tool in modern organic synthesis. While severalN-oxyl radicals have been developed to date, the lack of structural diversity for these species has hampered further progress in this field. Here we designed a novel class ofN-oxyl radicals based onN-hydroxybenzimidazole, and applied them to the direct C-H functionalization reactions. The flexibly modifiable features of these structures enabled facile tuning of their catalytic performance. Moreover, with these organoradicals, we have developed a metal-free approach for the synthesis of acyl fluoridesviadirect C-H fluorination of aldehydes under mild conditions.
Synthesis of Acyl Fluorides from Carboxylic Acids Using NaF-Assisted Deoxofluorination with XtalFluor-E
Gonay, Marie,Batisse, Chloé,Paquin, Jean-Fran?ois
, p. 10253 - 10260 (2020/08/12)
The synthesis of acyl fluorides using the deoxofluorination reaction of carboxylic acids using XtalFluor-E is described. This transformation, assisted by a catalytic amount of NaF, occurs at room temperature in EtOAc, where XtalFluor-E behaves as the activating agent and the fluoride source. A wide range of acyl fluorides were obtained in moderate to excellent yields (36-99%) after a simple filtration on a pad of silica gel. We also demonstrated that sequential deoxofluorination/amidation was possible.
Efficient cleavage of tertiary amide bonds: Via radical-polar crossover using a copper(ii) bromide/Selectfluor hybrid system
Maruoka, Keiji,Matsumoto, Akira,Wang, Zhe
, p. 12323 - 12328 (2020/12/08)
A novel approach for the efficient cleavage of the amide bonds in tertiary amides is reported. Based on the selective radical abstraction of a benzylic hydrogen atom by a CuBr2/Selectfluor hybrid system followed by a selective cleavage of an N-C bond, an acyl fluoride intermediate is formed. This intermediate may then be derivatized in a one-pot fashion. The reaction proceeds under mild conditions and exhibits a broad substrate scope with respect to the tertiary amide moiety as well as to nitrogen, oxygen, and carbon nucleophiles for the subsequent derivatization. Mechanistic studies suggest that the present reaction proceeds via a radical-polar crossover process that involves benzylic carbon radicals generated by the selective radical abstraction of a benzylic hydrogen atom by the CuBr2/Selectfluor hybrid system. Furthermore, a synthetic application of this method for the selective cleavage of peptides is described. This journal is
Synthesis of acyl fluorides via photocatalytic fluorination of aldehydic C-H bonds
Meanwell, Michael,Lehmann, Johannes,Eichenberger, Marc,Martin, Rainer E.,Britton, Robert
supporting information, p. 9985 - 9988 (2018/09/11)
Acyl fluorides are versatile acylating agents owing to their unique stability. Their synthesis, however, can present challenges and is typically accomplished through deoxyfluorination of carboxylic acids. Here, we demonstrate that acyl fluorides can be prepared directly from aldehydes via a C(sp2)-H fluorination reaction involving the inexpensive photocatalyst sodium decatungstate and electrophilic fluorinating agent N-fluorobenzenesulfonimide. This convenient fluorination strategy enables direct conversion of aliphatic and aromatic aldehydes into acylating agents.
Oxidation of primary aliphatic and aromatic aldehydes with difluoro(aryl)-λ3-bromane
Ochiai, Masahito,Yoshimura, Akira,Hoque, Md. Mahbubul,Okubo, Takuji,Saito, Motomichi,Miyamoto, Kazunori
supporting information; experimental part, p. 5568 - 5571 (2011/12/03)
Oxidation of primary aliphatic aldehydes with p- trifluoromethylphenyl(difluoro)-λ3-bromane in dichloromethane at 0 °C afforded acid fluorides selectively in good yields, while that of aromatic aldehydes in chloroform at room temperature produced aryl difluoromethyl ethers. A larger migratory aptitude of aryl groups compared to primary alkyl groups during a 1,2-shift from carbon to an electron-deficient oxygen atom in bromane(III) Criegee-type intermediates will result in these differences in the reaction courses.
