Umemoto’s Reagent II : A Powerful and Thermally Stable Trifluoromethylating Agent

Umemoto’s Reagent II (1), 2,8-diflouro-S-(trifluoromethyl)dibenzothiophenium salt has recently been reported as a new trifluoromethylating agent. Compared to Umemoto’s Reagent I (des-fluoro), Umemoto’s Reagent II shows superior thermal stability and electrophilicity. Under the basic condition, 1 smoothly reacts with β-dicarbonyl compounds to afford the corresponding trifluoromethylated products. The trifluoromethylation of 1 with terminal alkynes proceeds in the presence of a base and catalytic amounts of copper salts. Furthermore, 1 can be applied to the trifluoromethylation of various nucleophiles such as indoles, thiols and phosphines in the presence of base. 1 is a safe, solid trifluoromethylating agent that it is used for the synthesis of trifluoromethylated compounds which will attract attention in the pharmaceutical community.