Photoredox-Catalyst-Free Carboxylation of Unactivated Alkenes in DMSO: Synthesis of Polycyclic Indole Derivatives and Aliphatic Acids

A new method for the carboxylation of unactivated alkenes using CO₂ radical anions in the absence of a photoredox catalyst has been developed. The photocatalyst-free approach enables the efficient synthesis of polycyclic indole derivatives and linear carboxylic acids under mild conditions from HCO₂K with/without 1,4-diazabicyclo[2.2.2]octane (DABCO) in DMSO. This work demonstrates a significant advance in green chemistry, showcasing a catalyst-free approach for the functionalization of unactivated alkenes with cheap and readily available HCO₂K.