In commemoration of Prof. Togni’s 2017 ACS Award for Creative Work in Fluorine Chemistry, the speaker will talk about the advance in (trifluoromethyl)dibenzoheterocyclic onium salt chemistry. A series of S-, Se-, and Te-(trifluoromethyl)dibenzo-thio-, -seleno-, and -telluro-phenium salts were synthesized and demonstrated to be useful as power-variable electrophilic trifluoromethylating agents. Thus, a wide range of nucleophilic substrates such as carbanions, trialkylsilyl enol ethers, enamines, aromatics, heteroaromatics, acetylides, thiolates, phosphines, etc. were well trifluoromethylated by suitable combination of the substrate with the (trifluoromethyl)dibenzo onium salt. In addition, thermally unstable O-(trifluoromethyl)dibenzofuranium salts were synthesized in situ at low temperature and demonstrated to react with O- and N-nucleophiles such as alcohols, phenols, amines, anilines, and pyridines to give O- and N-trifluoromethylated products. For the last decade, many new trifluoromethylation reactions were developed by many synthetic organic chemists with S-(trifluoromethyl)dibenzothiophenium triflate and tetrafluoroborate called as Umemoto reagents. Umemoto reagents have been proved to have further wide application. However, Umemoto reagents are not practically useful electrophilic trifluoromethylating agents because of some significant drawbacks. Recently, a new version of Umemoto reagents, 2,8-difluoro- and 2,3,7,8-tetrafluoro-S-(trifluoromethyl)dibenzothiophenium salts have been developed as practically useful electrophilic trifluoromethylating agents.

Advance in (trifluoromethyl)dibenzoheterocyclic onium salt chemistry for electrophilic trifluoromethylating agents

253rd National Meeting (2017)

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