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Elemental Sulfur-Mediated Transformation of Carboxylic Acids to Acyl Fluorides by Electrophilic Fluorinating Reagent, Selectfluor

Elsayed M. Mahmoud, Soichiro Mori, Yuji Sumii and Norio Shibata*

*Department of Nanopharmaceutical Sciences, Nagoya Institute of Technology, Gokiso, Showa-Ku, Nagoya 466-8555, Japan, Email:

E. M. Mahmoud, S. Mori, Y. Sumii, N. Shibata, Org. Lett., 2023, 25, 2810-2814.

DOI: 10.1021/acs.orglett.3c00701

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Sulfur mediates a synthesis of acyl fluorides from carboxylic acids using Selectfluor. A broad range of acyl fluorides are accessible from carboxylic acids while avoiding the formation of acid anhydrides. 19F NMR spectra suggest that a S8-fluoro-sulfonium cation and a neutral S8-difluoride are generated in situ as reactive species in this deoxyfluorination reaction.

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proposed mechanism

Synthesis of acyl fluorides from carboxylic acids

The carboxylic acid 1 (0.2 mmol, 1.0 equiv) was added to a solution of Selectfluor® (0.3 mmol, 1.5 equiv) and S8 (0.3 mmol, 1.5 equiv) in dry MeCN (2.0 mL) in an oven-dried 10 mL glassware under N2 atmosphere, and the reaction mixture was stirred in oil bath heated at 80 °C for 4 h. The reaction mixture was then filtrated, and the filtrate was concentrated in vacuo. The crude product was analyzed by 19F NMR, and the residue was purified by flash column chromatography to afford acyl fluoride. Note: SO2 gas, which might be evolved from the reaction, is a toxic gas and all the work should be performed in a fume hood and a good-ventilated environment.

Key Words

Acyl Fluorides, Selectfluor

ID: J54-Y2023