Electrochemical synthesis of perfluoroalkanesulfinic acid derivatives

Abstract

It has been shown that perfluoroalkyl iodides react with thiolate anions under electrochemical initiation [N.V. Ignat'ev, S.D. Datsenko and L.M. Yagupolskii, Zh. Org. Khim. 27, No. 5, (1991) 905]. However, the reactivity of S- nucleophiles with sulfur atoms in a high oxidation state is much lower. We have studied the reaction of perfluoroalkyl halides with methyl sulphites. These compounds are easily prepared by bubbling of SO 2 through a sodium or lithium methylate solution: SO 2+NaOCH 3→CH 3OSO 2Na R FX CH 3OSO 2 −+2e −→ R FSO 2 −+CH 3O −+X − RCF 3, C 3F 7, C 8F 17; XI, Br The reaction of the anion −SO 2OCH 3 formed with the perfluoroalkyl halides under the electrochemical reduction conditions leads to the perfluoroalkane sulfinates in a high yield (95%). Though methyl sulphites contain two nucleophilic centres, sulfur and oxygen, the perfluoroalkyl radical attacks exclusively on the sulfur atom. This seems to be connected with the ‘hard’ oxygen centre. The treatment of the reaction mixture resulting from the electrochemical synthesis with chlorine leads to the formation of the corresponding perfluoroalkane sulfonyl chlorides, useful starting materials for the production of organofluorine compounds, in high yield: R FSO 2 −+Cl 2→R FSO 2Cl