Halogen migration vs. hydrogen halogenide elimination in reactions of 1-chloro-2,2,2-trifluoroethansulfonyl chloride and 1,2,2,2-tetrafluoroethansulfonyl fluoride with amines: theoretical and experimental investigation

A simple and useful method has been proposed for preparing of 1-chloro-2,2,2-trifluoroethan sulfonylchloride. By aminolysis of 1-chloro-2,2,2-trifluoroethansulfonylchloride the chlorine migration proceeds forming the corresponding salts of 1,1-dichloro-2,2,2-trifluoroethansulfinic acid. This process as well as the alternative reaction, elimination of hydrogen halogenide, has been studied using quantum chemistry (DFT and MP2) methods. As the calculation data indicate, an intermediately formed anion undergo intramolecular chlorine migration via a three-membered cyclic transition state. The latter is characterized by the low activation energy (ΔE = 27.0 kcal/mol). The barrier of activation in the case of 1,2,2,2-tetrafluoroethansulfonylfluoride is considerably higher (ΔE = 41.6 kcal/mol). The structures of the 1,1-dichloro-2,2,2-trifluoroethan sulfinic acid and 1,1,2,2,2-pentafluoroethansulfinic acid anions can be considered as donor–acceptor complexes of perhalogenoalkyl anions with SO2.