Sulfide‐Ene Reactions by Visible‐Light‐Mediated Phosphine Redox Catalysis

Sulfur‐containing compounds play a crucial role in many biological processes. The important gasotransmitter hydrogen sulfide (H 2 S) can be metabolized by cellular enzyme system for the biosynthesis of amino acids and regulatory effects related to diseases. Although the photocatalytic thiol‐ene reactions have been widely developed, a general H 2 S‐ene reaction by organic photocatalysis remains elusive. Inspired by enzyme‐catalyzed S N 2 dialkylation, we report a visible‐light‐mediated H 2 S‐ene radical dialkylation by phosphine redox catalysis. This challenge is addressed by the mechanism of photoexcited P (III) –P (V) cation‐catalyzed thiyl radical addition to alkenes. The H 2 S can be readily incorporated into a wide range of alkenes to access complex high‐value‐added sulfur‐containing scaffolds, especially the late‐stage functionalization of the alkenes derived from drugs and the cascade cyclization of dienes. This mild method also performs very well in the thiol‐ene reactions, which are further applied to the synthesis of unsymmetric thioethers, macrocyclic sulfides, the conjugation of biomolecules, and sulfur‐containing drugs. This strategy holds significant promise in the bioconjugation and the discovery of bioactive organosulfur compounds.