Trifluoromethylthiolation [Synthetic Reagents]

　The trifluoromethylthio group (CF₃S-) has attracted attention as a potentially-significant functional group in the pharmaceutical and agrochemical fields because of its strong electron-withdrawing effect and high lipophilicity. Some methods for direct trifluoromethylthiolation have been developed and one of them, copper(I) trifluoromethanethiolate (CuSCF₃) [C1159] is an effective nucleophilic trifluoromethylthiolating reagent. On the other hand, a simple electrophilic reagent, trifluoromethylsulphenyl chloride (CF₃SCl) is gaseous and highly toxic, so it is hardly used now.
　Recently, some electrophilic trifluoromethylthiolating reagents which are safer to use and easier to handle, have been reported. Both N-Methyl-N-(trifluoromethylthio)aniline [M2595]¹⁾ developed by Billard et al. and N-(trifluoromethylthio)phthalimide [T3143]²⁾ developed by Rueping are useful electrophilic trifluoromethylthiolating reagents because their states are liquid and solid respectively. In addition, Shibata et al. have developed a hypervalent iodonium ylide having a trifluoromethanesulfonyl group [P2143], and used it for the electrophilic trifluoromethylthiolation. In this reaction, it seems that the trifluoromethylthiocation species generated in situ by the reduction of P2143 acts as an electrophilic trifluoromethylthiolating reagent for enamines, indoles and β-ketoesters.³⁾