Difluoromethylation of Aryl Iodides using a (NHC)Cu(CHF₂) Complex

Sanford et al. have reported that difluoromethylations using a (NHC)Cu(CHF2) complex (3) can be prepared/isolated from a copper(I) / N-heterocyclic carbene (NHC) complex of chloro[1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]copper(I) (1) and (difluoromethyl)trimethylsilane (2). According to their report, previously isolated Cu(I) complex 3 stoichiometrically reacts with various functional group’s substituted aryl iodides and affords the corresponding difluoromethylated compounds in good yield. While, in the presence of cesium fluoride, this reaction can be applied to the catalytic difluoromethylation by the use of catalytic amounts of Cu(I) complex 1 and 2 equivalents of 2 as a difluoromethane source. In general, difluoromethylated copper(I) complex species (“Cu(I)-CHF2”) are considered to be unstable and difficult to isolate. However, this report shows isolation of that Cu(I) species by complexation as a (NHC)Cu(CHF2) complex using a NHC ligand.