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.