Photoredox and Weak Brønsted Base Dual Catalysis: Alkylation of α-Thio Alkyl Radicals

We report the C–H activation of thioethers to α-thio alkyl radicals and their addition to electron-deficient olefins to afford alkylated products through dual photoredox and weak Brønsted base catalysis. Mechanistic studies are consistent with a two-step activation mechanism, where oxidation of thioethers to their corresponding sulfide radical cations by an acridinium photoredox catalyst is followed with deprotonation by trifluoroacetate to generate α-thio alkyl radicals and trifluoroacetic acid (TFA). Experimental studies support the involvement of TFA in all subsequent steps leading to product formation.