Visible-Light-Induced, Copper-Catalyzed Three-Component Coupling of Alkyl Halides, Olefins, and Trifluoromethylthiolate To Generate Trifluoromethyl Thioethers

Photoinduced, copper-catalyzed coupling reactions are emerging as a powerful method for generating Csp3-Y (Y = C or heteroatom) bonds from alkyl electrophiles and nucleophiles. Corresponding three-component couplings of alkyl electrophiles, olefins, and nucleophiles have the potential to generate an additional Csp3-Y bond and to efficiently add functional groups to both carbons of an olefin, which serves as a readily available linchpin. In this report, we establish that a variety of electrophiles and a trifluoromethylthiolate nucleophile can add across an array of olefins (including styrenes and electron-poor olefins) in the presence of CuI/binap and blue-LED irradiation, thereby generating trifluoromethyl thioethers in good yield. The process tolerates a wide range of functional groups, and an initial survey of other nucleophiles (i.e., bromide, cyanide, and azide) suggests that this three-component coupling strategy is versatile. Mechanistic studies are consistent with a photoexcited Cu(I)/binap/SCF3 complex serving as a reductant to generate an alkyl radical from the electrophile, which likely reacts in turn with the olefin and a Cu(II)/SCF3 complex to afford the coupling product.