Synthesis of Unsymmetrical Disulfides via Photocatalytic Hydrodisulfuration

Photoredox catalysis is an appealing strategy for the C–S bond formation. Herein, we disclose the photocatalytic reductive hydrodisulfuration of electron-deficient alkenes for the synthesis of unsymmetrical disulfides. Mechanistic studies indicate that while the radical initiation occurs in this reaction, the perthiolate anion generated from the reduction of tetrasulfides via single-electron transfer is the key electron donor for the conjugate addition. This methodology exhibits broad functional group tolerance and allows the late-stage installation of disulfide motifs into marketed drugs and the preparation of peptides containing the disulfide bond under cysteine-free conditions. Moreover, the mechanism of ionic addition is further explained by control experiments and computations.