Direct Cupration of Fluoroform
2011-12-28T00:00:00Z (GMT) by
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).