Visible‐Light Photoredox‐Catalyzed Pyridylphosphination of Alkenes to Access β‐Pyridylalkylated Phosphine Sulfides ^†

Comprehensive Summary Visible‐light photoredox‐catalyzed sulfidation reactions with elemental sulfur have emerged as a mild and attractive strategy to construct sulfur‐containing compounds in organic synthetic chemistry. Herein, visible‐light‐induced pyridylphosphination of alkenes with 4‐cyanopyridines, secondary phosphines, and elemental sulfur leading to β‐pyridylalkylated phosphine sulfides has been developed. The present photocatalytic pyridylphosphination reaction can incorporate both pyridine and phosphine sulfide structural units into the same molecular framework under mild conditions by using elemental sulfur as sulfur source, in which P=S, C–P, and C–C bonds were successfully constructed in a single operation. A preliminary mechanistic investigation shows that diphenylphosphine sulfide might be the key intermediate and a photocatalytic phosphonyl radical‐participated process was involved in this transformation. This visible‐light‐promoted protocol has the advantages of clean energy source, mild condition, broad substrate scope and good compatibility of functional groups.