Photoredox-Catalyst-Free\nCarboxylation of Unactivated\nAlkenes in DMSO: Synthesis of Polycyclic Indole Derivatives and Aliphatic\nAcids

A new method for the carboxylation of unactivated alkenes\nusing\nCO<sub>2</sub> radical anions in the absence of a photoredox catalyst\nhas been developed. The photocatalyst-free approach enables the efficient\nsynthesis of polycyclic indole derivatives and linear carboxylic acids\nunder mild conditions from HCO<sub>2</sub>K with/without 1,4-diazabicyclo[2.2.2]octane\n(DABCO) in DMSO. This work demonstrates a significant advance in green\nchemistry, showcasing a catalyst-free approach for the functionalization\nof unactivated alkenes with cheap and readily available HCO<sub>2</sub>K.