Visible Light Photoredox Catalysis with CO2: Difunctionalization of Terminal Alkynes

Comprehensive Summary The development of carbon dioxide (CO 2 ) capture and utilization is of vital importance. However, previous photocatalytic reduction reactions for converting CO 2 into chemicals ( e.g ., CO, HCOOH, CH 4 , or CH 3 OH) rely heavily on sacrificial reagents. Herein, we disclose a visible light photoredox‐catalyzed 1,2‐difunctionalization of terminal alkynes by using CO 2 as an ideal quenching reagent and the xanthene dye Rhodamine 6G (Rh‐6G) as a photocatalyst (PC) via consecutive photoinduced electron transfer (ConPET) process. The newly developed CO 2 ‐triggered reaction provides a highly regio‐ and stereo‐selective approach to diverse functionalized ( E )‐α‐vinylsulfones with simultaneously efficient conversion of CO 2 into oxalate. The practicality of this protocol is demonstrated by late‐stage modification of alkynes derived from biologically active natural products or drugs. Preliminary mechanistic studies suggest that the homocoupling of CO 2 radical anion results in the formation of oxalate.