Two research groups reported trifluoromethylations of diazonium salts in 2013. Goossen reported the preparation of a  complex from CuSCN, , and . In contrast, Fu reported the trifluoromethylation using Umemotos reagent (S'-trifluoromethyldibenzothiophenium tetrafluoroborate) and Cu powder (Gattermann-type conditions). They can be described by the following equation:
The bracket indicates that other ligands on copper are likely present but are omitted.