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

Area of Science:

• Organic Chemistry
• Photocatalysis
• Green Chemistry

Background:

• Carbon dioxide (CO2) is an abundant C1 resource, but its direct utilization remains challenging.
• Developing efficient catalytic systems for CO2 functionalization is crucial for sustainable chemistry.
• Radical anions, like the carbon dioxide radical anion (CO2•−), are highly reactive intermediates in organic synthesis.

Purpose of the Study:

• To develop a visible-light-driven carboxylation of benzyl bromides using CO2.
• To synthesize high-value arylacetic acids under mild and sustainable conditions.
• To explore the use of potassium formate as a cost-effective terminal reductant.

Main Methods:

• Visible-light photocatalysis employing a specific iridium complex (Ir(ppy)2(dtbbpy)PF6) as the photosensitizer.
• Utilizing potassium formate as both a hydrogen atom source and a terminal reductant.
• Carboxylation reactions performed under mild conditions with a wide range of benzyl bromide substrates.
• Mechanistic studies involving radical intermediates (CO2•−) and photo-oxidation processes.

Main Results:

• Successful synthesis of arylacetic acids via visible-light-mediated carboxylation of benzyl bromides.
• Demonstrated mild reaction conditions and broad substrate applicability.
• Potassium formate effectively served as a terminal reductant, facilitating the generation of the CO2 radical anion.
• Mechanistic investigations supported a pathway involving the CO2 radical anion.

Conclusions:

• A novel and efficient visible-light-driven carboxylation of benzyl bromides has been established.
• This method provides a sustainable route to valuable arylacetic acids using CO2 as a C1 source.
• The use of potassium formate offers an economical and accessible approach for this transformation.