text: In electrophilic trifluoromethylation the active trifluoromethyl donor group carries a positive charge. Production of an CF cation has been described as "extremely hard"  The first relevant reagent, a diaryl(trifluoromethyl) sulfonium salt (ArSCFSbF) was developed in 1984 by reaction of an aryltrifluoromethyl sulfoxide 1 with SFSbF followed by reaction with an electron-rich arene. The reagent was used in trifluoromethylation of a thiophenolate.
  S-(trifluoromethyl)dibenzothiophenium tetrafluoroborate is a commercially available and known trifluoromethylation reagent based on the same principle first documented in 1990. In this type of compound sulfur has been replaced by oxygen, selenium and tellurium. Examples of substrates that have been investigated are pyridine, aniline, triphenylphosphine and the lithium salt of phenylacetylene.
  Another group of trifluoromethyl donors are hypervalent iodine(III)–CF reagents for example 3,3-dimethyl-1-(trifluoromethyl)-1,2-benziodoxole. Some of these are known as Togni reagents, such as Togni reagent II. Substrates are thiols, alcohols, phosphines, (hetero) arenes, unactivated olefins and unsaturated carboxylic acids.
  The reaction mechanism of electrophilic trifluoromethylations has been described as controversial with polar substitution or single electron transfer as likely candidates.