New kinds of organic superacids. Bis(perfluoroalkylsulfonylimino)trifluoromethanesulfonic acids and their trimethylsilyl esters

Abstract

A synthesis of new unsymmetric trifluoromethylsulfonylimino(nonafluoro-n-butyl-sulfonylimino)trifluoromethanesulfonic acid (1b) is reported. During the silylation reactions studies of bis(perfluoroalkylsulfonylimino)trifluoromethanesulfonic acids (1a,b) it was shown that reaction proceeds exclusively on the central oxygen atom to give trimethylsilyl esters. The obtained esters along with several trimethylsilylesters of sulfonic acids have been studied by ²⁹Si-NMR spectroscopy and an attempt to estimate the strength of bis(perfluoroalkylsulfonylimino)trifluoromethanesulfonic acids by the ²⁹Si-NMR chemical shifts of their trimethylsilylesters was made, resulting in the conclusion that these compounds may be cited as the strongest organic Brønsted acids.