Direct Cupration of Fluoroform

We have found the first reaction of direct cupration of fluoroform, the most attractive CF<sub>3</sub> 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 CF<sub>3</sub>H at room temperature and atmospheric pressure to give CuCF<sub>3</sub> derivatives. The CuCl and <i>t</i>-BuOK (1:2) combination provides best results, furnishing the CuCF<sub>3</sub> product within seconds in nearly quantitative yield. As demonstrated, neither CF<sub>3</sub><sup>–</sup> nor CF<sub>2</sub> mediate the Cu–CF<sub>3</sub> bond formation, which accounts for its remarkably high selectivity. The fluoroform-derived CuCF<sub>3</sub> solutions can be efficiently stabilized with TREAT HF to produce CuCF<sub>3</sub> 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-<i>t</i>)<sub>2</sub>] (<b>1</b>), Na(DMF)<sub>2</sub>[Cu(OBu-<i>t</i>)<sub>2</sub>] (<b>2</b>), [K<sub>8</sub>Cu<sub>6</sub>(OBu-<i>t</i>)<sub>12</sub>(DMF)<sub>8</sub>(I)]<sup>+</sup> I<sup>–</sup> (<b>3</b>), and [Cu<sub>4</sub>(CF<sub>3</sub>)<sub>2</sub>(C(OBu-t)<sub>2</sub>)<sub>2</sub>(μ<sup>3</sup>-OBu-t)<sub>2</sub>] (<b>7</b>).