Photoredox‐Catalyzed Three‐Component Reaction of Acetoacetic Ester, Styrenes, and CO ₂ : The Impact of External and Internal Factors

We have shown for the first time that the visible‐light‐driven photocatalytic three‐component reaction of ethyl acetoacetate, styrene, and CO ₂ affords two carboxylation products. The ratio of these products is determined by the CO ₂ pressure. Specifically, at 1.5 bar, the product ratio (4‐aryl‐2‐acetylglutaric acid to 2‐(2‐aryl‐3‐oxobutyl)malonic acid) for unsubstituted styrene is 32: 63 . However, at 5.5 bar, this ratio shifts to 72 :25. The impact of the substituents on the styrene ring is also noteworthy. Electron‐withdrawing substituents favor the first carboxylation product, providing yields up to 95% ( p ‐CF ₃ , 5.5 bar CO ₂ ), while electron‐donating substituents promote rearrangement, leading predominantly to the isomeric product in yields up to 71% ( p ‐OMe, 1.5 bar CO ₂ ). The reaction proceeds at room temperature without transition metals, using an organic photocatalyst (4DPAIPN) and a base. The reaction pathway is dictated by both internal and external factors, namely the CO ₂ pressure and the electronic nature of the styrene substituent.