An efficient approach to the synthesis of 2,3,4,5-tetrafluorophenol

A new method for the preparation of 2,3,4,5-tetrafluorophenol from 2-[(2,3,4,5,6-pentafluorophenyl)thio]acetic acid has been proposed. It included the intramolecular cyclization of the salt of this acid in the presence of K2CO3 with the substitution of the ortho fluorine atom and the formation of a lactone, which under the reaction conditions underwent the ring-opening with the formation of the potassium salt of 2-[6-hydroxy(2,3,4,5-tetrafluorophenyl)-thio]acetic acid. The resulting salt was converted into methyl ester and desulfurized with Raney nickel to 2,3,4,5-tetrafluorophenol. The proposed method is a simple and efficient way to obtain poorly available 2,3,4,5-tetrafluorophenol in similar to 58% total yield based on 2-[(2,3,4,5,6-pentafluorophenyl)thio]acetic acid.