Copper‐Catalyzed 1,2‐Bistrifluoromethylation of Terminal Alkenes

Abstract Many efficient catalytic methods for the introduction of trifluoromethyl group (CF 3 ) have been reported. Among them, the addition of CF 3 and other components to alkenes is well known, and many components such as azides, cyanides, amines, and halides have been inserted into alkenes with CF 3 . However, to date the double catalytic insertion of CF 3 into an alkene is unknown. Herein, we report the catalytic 1,2‐bistrifluoromethylations of alkenes catalyzed by Copper (Cu). We used two CF 3 sources, namely Umemoto's reagent and (trifluoromethyl)trimethylsilane (TMSCF 3 ). Each reagent plays a unique role during this transformation; Umemoto's reagent generates CF 3 radicals, while TMSCF 3 is used to form CF 3 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 CF 3 radical to the alkene, to the corresponding alkyl cation, which then reacts with the CF 3 anion from TMSCF 3 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. magnified image