Trifluoroacetic anhydride-sodium iodide reagent. Nature and applications

Trifluoroacetic anhydride - sodium iodide mixture (TFAA-NaI; TFAA-I) reacts with several compounds bearing semipolar X-O bond, usually in the mode of deoxygenation, with liberation of iodine. The results of systematic investigations of the TFAA-I-reaction with various types of S-oxo and N-oxo compounds were discussed. The majority of these reactions are characterized by quantitative course, with respect to both X-O substrate transformation as well as to the amounts of liberated iodine. On this basis, a variety of sulphoxides and sulphimides were successfully reduced to sulphides and/or arene-N-oxides to amines, using TFAA-I at ambient temperature. Arene- and alkyl-sulphonic acids were reduced to the corresponding thiol derivatives in moderate yields. Stoichiometric course of the TFAA-I reaction with several S-oxo and N-oxo compounds gave origin to their analytical determinations. Thus, due to stoichiometric amounts of iodine formed from sulphoxides, sulphimides, arene-N-oxides, nitrones and nitroxide radicals, and nitroso compounds - the TFAA-I reagent can be applied to their analytical determination (titrimetric on µmol and spectrometric on nmol scale) and/or TLC detection.