Redox-neutral Photocatalytic C-H Carboxylation of Arenes and Styrenes with CO2

Abstract

Carbon dioxide (CO<sub>2</sub>) is an attractive one-carbon (C1) building block in terms of sustainability and abundance. However, its low reactivity limits applications in organic synthesis as typically high-energy reagents are required to drive transformations. Here, we present a redox-neutral C−H carboxylation of arenes and styrenes using a photocatalytic approach. Upon blue-light excitation, the anthrolate anion photocatalyst is able to reduce many aromatic compounds to their corresponding radical anions, which react with CO<sub>2</sub> to afford carboxylic acids. High-throughput screening and computational analysis suggest that a correct balance between electron affinity and nucleophilicity of substrates is essential. This novel methodology enables the carboxylation of numerous aromatic compounds, including many that are not tolerated in classical carboxylation chemistry. Over 50 examples of C−H functionalizations using CO<sub>2</sub> or ketones illustrate a broad applicability. The method opens new opportunities for late-stage C−H carboxylation and valorization of common arenes.

Photo-Induced Thiolate Catalytic Activation of Inert Caryl-Hetero Bonds for Radical Borylation

“…Continuing our research interest in exploring the reducing ability of anionic species in photoredox catalysis, 41,42 we wondered whether we could generate aryl radicals from inert bonds (C aryl −F, C aryl −O, C aryl -N and C aryl −S bonds) for borylation by using a sulfur-centered anion (e.g., thiolate) as a photocatalyst. The proposed catalytic system was inspired by our previous finding wherein thiolate could efficiently shuttle electrons from the boronate radical anion, a species that is produced in radical borylation processes, to the photocatalytic system.…”