Activation of Trifluoromethylthio Moiety by Appending Iodonium Ylide under Copper Catalysis for Electrophilic Trifluoromethylation Reaction

A novel iodonium‐ylide compound 2 that appends atrifluoromethylthio (SCF 3 ) group is disclosed as a new, shelf‐stable electrophilic trifluoromethylation reagent. Unlike known shelf‐stable electrophilic trifluoromethylation reagents, 2 has a stable SCF 3 group which is activated by appending iodonium ylide under copper catalysis via sulfonium ylide to generate a cationic trifluoromethyl (CF 3 ) species. Reagent 2 was found to be an efficient electrophilic trifluoromethylation reagent for a wide range of silyl enol ethers 3 under copper catalysis. Cyclic and acyclic α ‐trifluoromethyl ketones 4 were obtained by reagent 2 in moderate to good yields. On the other hand, a difluoromethylthio analogue 5 did not affect intermolecular transfer difluoromethylation to substrates. Instead, intramolecular 1,4‐migration proceeded similar to the Stevens rearrangement to provide 6 in 21% yield, independent of the presence of nucleophiles 3 .