Copper-Catalyzed 1,2-Bistrifluoromethylation of Terminal Alkenes

Many efficient catalytic methods for the introduction of trifluoromethyl group (CF3) have been reported. Among them, the addition of CF3 and other components to alkenes is well known, and many components such as azides, cyanides, amines, and halides have been inserted into alkenes with CF3. However, to date the double catalytic insertion of CF3 into an alkene is unknown. Herein, we report the catalytic 1,2-bistrifluoromethylations of alkenes catalyzed by Copper (Cu). We used two CF3 sources, namely Umemoto's reagent and (trifluoromethyl) trimethylsilane (TMSCF3). Each reagent plays a unique role during this transformation; Umemoto's reagent generates CF3 radicals, while TMSCF3 is used to form CF3 anions. Copper (I) bromide (CuBr) exhibited the best catalytic activity for this reaction. We believe that CuBr oxidizes the alkyl radical, which is produced by the addition of the CF3 radical to the alkene, to the corresponding alkyl cation, which then reacts with the CF3 anion from TMSCF3 to produce the desired product. This reaction tolerates a diverse set of substrates bearing functional groups such as amides, esters, ethers, ketones, protected amines, tertiary amines, and phthalimides; hence this transformation is widely applicable to a wide variety of substrates.