Z-Selective Synthesis of α-Sulfanyl Carbonyl Compounds from Internal Alkynes and Thiols via Photoredox Catalysis

A synthetically useful Z-selective cascade formal thiyl radical addition, 1,3-double bond isomerization, oxygen trapping reaction, can be promoted by Eosin B under visible light, leading to the construction of 2-aryl- and alkylthio enone derivatives in good yields. An accurate study on the reactivity of different thiols and the screening of the reaction conditions, allowed us to extend this reaction to a large number of substrates, showing a good functional groups tolerance while highlighting the limitations of this procedure. Background experiments and mechanistic studies were also. performed to rationalize this cascade process. The usefulness of this methodology was finally demonstrated via the transformation of a series of α-sulfanyl-enone adducts through selected oxidation reactions, stereoselective synthesis of cyclopropyl ketones, indanones, and pyrazole compounds.