Bismuth(III) Trifluoromethanesulfonate: An Efficient Catalyst for the Sulfonylation of Arenes

Abstract

Sulfonylation reactions are one of the most important groups of aromatic electrophilic substitutions.1 The sulfonyl group is a widely used synthon for synthetic organic chemists,2 and sulfones have many industrial applications.3 In Friedel-Crafts (FC) acylation and sulfonylation, a consequence of the complexation of the Lewis acid with the reaction product implies that a stoichiometric amount of the activator is often required. However, some metal halides such as iron(III) chloride,1 Bronsted acids, for example polyphosphoric acid4 or triflic acid,5 and zeolites6,7 have been reported to catalyze the sulfonylation of arenes. In recent years, rare earth trifluoromethanesulfonates (triflates) have been reported for the catalysis of the FC acylation8 but not for the catalysis of the FC sulfonylation. Also, our laboratory reported that bismuth(III) chloride (1a) and particularly bismuth(III) triflate (1b) were catalysts for acylation reactions,9 especially for FC acylation.10 In a stoichiometric process from arylsulfonyl bromides, silver triflate gives trifluoromethanesulfonic arenesulfonic anhydrides (ArSO2OTf), which are strong sulfonylating reagents.11 We present here a study of the catalytic activity of 1a and 1b for the sulfonylation reaction of arenes (eq 1), for which 1b proved to be a metal triflate capable of realizing an outstanding catalytic process.