fac-Re(2,2'-bipyridine)(CO)3Cl Catalyzes Visible-Light-Driven Functionalization of an Organic Substrate with CO2.

The molecular photocatalyst fac-Re-(2,2'-bipyridine)-(CO)₃Cl ([Re-Cl]) is well established and has been extensively investigated for the highly active and selective conversion of CO₂ to CO. However, its reactivity in processes other than CO₂ reduction has rarely been explored. Herein, we report the application of [Re-Cl] as a catalyst for the visible-light-driven carboxylation of an alkene using CO₂, with phenyl vinyl sulfone (1) serving as a model substrate. The catalytic system successfully catalyzed the carboxylation of 1 to its corresponding carboxylic acid, with complete suppression of CO formation throughout the reaction. A turnover number (TON) of up to 2600, along with excellent regioselectivity, was achieved under optimized conditions. Control experiments revealed the key role of each reaction component, while isotope labeling with ¹³CO₂ confirmed that the carboxyl group originated from CO₂. Furthermore, mechanistic investigations suggested that the Re-CO₂ intermediate reacts directly with the alkene. These findings highlight the potential of Re-based molecular complexes for broader reactivities and expand their applicability in sustainable synthetic transformations.