Electrochemical Synthesis of β-Keto Sulfonyl Fluorides via Radical Fluorosulfonylation of Vinyl Triflates

Qingyuan Feng, Yuanyuan Fu, Yu Zheng, Saihu Liao and Shenlin Huang*

*Nanjing Forestry University, Nanjing 210037, People’s Republic of China, Email: shuangnjfu.edu.cn

Q. Feng, Y. Fu, Y. Zheng, S. Liao, S. Huang, Org. Lett., 2022, 24, 3702-3706.

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Abstract

An electroreductive protocol for the radical fluorosulfonylation of vinyl triflates with FSO₂Cl as the fluorosulfonyl radical source uses inexpensive graphite felt as electrodes, thus avoiding the use of a sacrificial anode. This metal-free protocol offers mild conditions, easy scalability and provides valuable β-keto sulfonyl fluorides from readily available precursors.

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proposed mechanism

Electrochemical Synthesis of β-Ketosulfonyl Fluorides - Experimental Procedure and Reaction Setup

A three necked round bottom flask (25 mL) (Figure below) equipped with two graphite felt electrodes (20 mm x 10 mm x 1 mm), and a stir bar was charged with Et₄NPF₆ (421 mg, 0.15 M), anhydrous Et₂O (10 mL, 0.02 M) and 1 (0.2 mmol). Then, ClSO₂F was added (0.32 mmol, 1.6 eq, 1 M in anhydrous PhCF₃). The mixture was electrolyzed at a constant voltage of 15 V for 6 h. Subsequently, the reaction was quenched with water and electrodes were rinsed with EtOAc. The resulting mixture was extracted with EtOAc and the combined organic layers were dried over Na₂SO₄ and concentrated in vacuo. The residue was purified by column chromatography to afford the desired product.

(A) and (B) Graphite felt electrode (20 mm x 10 mm x 1 mm). (C) and (D) Standard reaction unit. (E) The reaction mixture after 6 h of electrolysis.

Key Words

sulfonyl fluorides, electrochemistry

ID: J54-Y2022