Regioselective Electrochemical Fluorination of Open-Chain Dithioacetal Derivatives Bearing Electron-Withdrawing Substituents at the α-Position: Product Selectivity Depending on Supporting Fluoride Salts

Selective fluorination of organic molecules is of much importance to develope new pharmaceuticals and agrochemicals.   We have systematically studied electrochemical fluorination of various heteroatom compounds including heterocycles.^1-3)

In this study, we have investigated fluorinated product selectivity depending on ionic liquid fluoride salts.Anodic fluorination of dithioacetals bearing various electron-withdrawing substituents was achieved with high regioselectivity in the presence of Et₃N-3HF to give α-fluorinated products in good to excellent yields. On the other hand,Et₃N-5HF and Et₄NF-5HF containing high HF content was used as a fluorinating reagent, fluorodesulfurization of dithioacetals such as ethyl α,α-bis(phenylthio)acetate and α,α-bis(phenylthio)acetone was promoted markedly; however, α-fluorination of α,α-bis(phenylthio)acetonitrile proceeded without desulfurization exclusively to provide the corresponding α-monofluorinated product in excellent yield regardless of fluoride salts.

References:

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3) Takahashi, K.; Inagi, S.; Fuchigami, T. J. Electrochem. Soc. 2013, 160, G3046.