Benzylic C(sp 3 )H Perfluoroalkylation of Six‐Membered Heteroaromatic Compounds

Successful benzylic C(sp 3 )H trifluoromethylation, pentafluoroethylation, and heptafluoropropylation of six‐membered heteroaromatic compounds were achieved as the first examples of a practical benzylic C(sp 3 )H perfluoroalkylation. In these reactions, BF 2 C n F 2 n +1 ( n =1–3) functioned as both a Lewis acid to activate the benzylic position and a C n F 2 n +1 ( n =1–3) source. The perfluoroalkylation proceeded at both terminal and internal positions of the alkyl chains. Perfluoroalkylated products were obtained in moderate to excellent yields, even on gram scale, and in a sequential procedure without isolation of the intermediates. By using this method, trifluoromethylation of a bioactive compound, as well as introduction of a CF 3 group into a bioactive molecular skeleton, proceeded regioselectively.