Trifluoromethylation of aliphatic halogen compounds

Aryl, heteroaryl or vinyl halides can be trifluoromethylated using CF3CO2Na–Cul. With alkyl iodides, however, the method fails, yielding trifluoroacetyl esters instead. Allylic halogens can be substituted with Burton's reagent, obtained from dihalogenodifluoromethane via CF3CdHal and transmetallation with Cul. A new access to trifluoropropionic acid is thereby found. Prop-2-ynyl bromide produces trifluoromethylallene. Attempts at trifluoromethylation of bromoacetate with CF3CO2Na–Cul in NMP (N-methyl-2-pyrrolidone) solution led to formation of the trifluoroacetoxy derivative and of a formal adduct of hexafluoroacetone to the α position of NMP.