Direct Cupration of Fluoroform

We have found the first reaction of direct cupration of fluoroform, the most attractive CF₃ source for the introduction of the trifluoromethyl group into organic molecules. Treatment of CuX (X = Cl, Br, I) with 2 equiv of MOR (M = K, Na) in DMF or NMP produces novel alkoxycuprates that readily react with CF₃H at room temperature and atmospheric pressure to give CuCF₃ derivatives. The CuCl and t-BuOK (1:2) combination provides best results, furnishing the CuCF₃ product within seconds in nearly quantitative yield. As demonstrated, neither CF₃^– nor CF₂ mediate the Cu-CF₃ bond formation, which accounts for its remarkably high selectivity. The fluoroform-derived CuCF₃ solutions can be efficiently stabilized with TREAT HF to produce CuCF₃ reagents that readily trifluoromethylate organic and inorganic electrophiles in the absence of additional ligands such as phenanthroline. A series of novel Cu(I) complexes have been structurally characterized, including K(DMF)[Cu(OBu-t)₂] (1), Na(DMF)₂[Cu(OBu-t)₂] (2), [K₈Cu₆(OBu-t)₁₂(DMF)₈(I)]⁺ I^– (3), and [Cu₄(CF₃)₂(C(OBu-t)₂)₂(μ³-OBu-t)₂] (7).