Visible-Light-Driven Reductive Carboxylation of Benzyl Bromides with Carbon Dioxide Using Formate as Terminal Reductant

Cheap and available formate can be seen formally as a carbon dioxide radical anion (CO2 center dot-) combined with a hydrogen atom, where the CO2 center dot- is not only a highly active radical but also a very powerful reductant. In this paper, we successfully realized a visible-light-driven carboxylation of benzyl bromides with carbon dioxide to prepare high-value arylacetic acids using potassium formate as a terminal reductant. This reaction is characterized by mild reaction conditions and a wide range of substrates. Moreover, under nitrogen atmosphere, the reaction can also achieve the carboxylation of benzyl bromides utilizing an excess of potassium formate. Mechanistic experiments indicate this carboxylation proceeded through CO2 center dot-, which was generated from the oxidation of 1,4-diazabicyclo[2.2.2]octane with excited photosensitizer Ir(ppy)(2)(dtbbpy)PF6 in the presence of the potassium formate.

Automated summary

In this study, a visible-light-driven carboxylation reaction was successfully achieved to produce high-value arylacetic acids using benzyl bromides and carbon dioxide as starting materials. The reaction conditions are mild and the substrate scope is broad.