Benchmark and Solvent-Free Preparation of Sulfonium Salt Based Electrophilic Trifluoromethylating Reagents

Here we describe work devoted to the one-pot preparation of electrophilic trifluoromethylating reagents. The first part describes a reappraisal of our earlier experimental conditions and leads to an improved protocol that avoids the use of solvent and allows better yields. The second part carefully studies the behavior of biaryl substrates, whose structures can drive the reaction through the formation of original noncyclic or tricyclic dibenzothiophenium salts. New compounds were tested, in a standard reaction with aniline, for their trifluoromethylating power and revealed equivalent or improved reactivity relative to that of existing reagents. Furthermore, contrary to common knowledge, the presence of electron-donating methyl groups gave reagents with very high activity. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)