Carbon dioxide (CO2) is a notorious greenhouse gas while it is also a promising building block in synthetic chemistry due to its abundance, easy availability, nontoxicity, and recyclability. However, the inert nature of CO2 has set barrier for its efficient chemical transformation. Recently, photochemistry has provided a sustainable, benign, and powerful way for carboxylation with CO2 under mild conditions by using photons as energy source.
In particular, the visible-light driven carboxylation of aryl halides with CO2 is attractive due to the importance of aryl carboxylic acid derivatives and the easy access of diverse aryl (pseudo)halides. In contrast to traditional ways where reactive but metallic reductants or sacrificial electrodes are always involved, the photocatalytic process features mild conditions with mild electron donors. In such field, Iwasawa, König, Jana and others contributed significantly by realizing carboxylation of aryl carbon-heteroatom bonds in various aryl (pseudo)halides via photoredox/transition metal dual catalysis. Despite of the great achievements, there is no report on visible-light photoredox-catalyzed carboxylation of aryl C−F bonds with CO2. Thus, the development of visible-light photocatalytic carboxylation of aryl C−F bonds with CO2 with high selective is urgent but extremely challenging.
Fluorine chemistry has important applications in human production and life. C−F bond functionalization is important to convert readily available polyfluoroarenes to partially fluorinated compounds, which are highly valuable but less accessible. Polyfluoroaryl carboxylic acids and derivatives are privileged structures in pharmaceuticals, agricultures, and organic functional materials. It is a promising way to construct polyfluoroaryl carboxylic acids with green CO2 under mild conditions via photocatalysis. However, such strategy may face great challenges. First, aryl C−F bonds are very strong in nature which set barriers for efficient cleavage. Second, the chemical inertness of CO2 makes it difficult for efficient cross coupling with C−F bonds. Finally, photocatalysis would introduce instable and untamable radical intermediates which usually cause diverse side reactions that are hard to suppress.
Recently, a research group led by Prof. Da-Gang Yu from Sichuan University, China reported the first visible-light photoredox-catalyzed selective carboxylation of C(sp2)−F bonds in polyfluoroarenes with CO2. Such work features wide and challenging substrate scope including penta-, tetra- and trifluorinated arenes with moderate to high yields. What’s more, such transformation can pick up one particular C(sp2)−F bond from the others with benign selectivity. Furthermore, several natural product derivatives and fluorine-containing liquid crystal molecules were also amenable to such transformation, suggesting its practical utilization. Finally, it is interesting to harness instable aryl radical intermediates to be reduced into aryl anions to trigger following carboxylation process. In a bigger picture, the finding in mechanism may open a new avenue for aryl C−F bond functionalization, with more variety of new chemical transformations possible in the future. The results were published in Chinese Journal of Catalysis (https://doi.org/10.1016/S1872-2067(22)64140-8).
About the Journal
Chinese Journal of Catalysis is co-sponsored by Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Chinese Chemical Society, and it is currently published by Elsevier group. This monthly journal publishes in English timely contributions of original and rigorously reviewed manuscripts covering all areas of catalysis. The journal publishes Reviews, Accounts, Communications, Articles, Highlights, Perspectives, and Viewpoints of highly scientific values that help understanding and defining of new concepts in both fundamental issues and practical applications of catalysis. Chinese Journal of Catalysis ranks among the top two journals in Applied Chemistry with a current SCI impact factor of 12.92. The Editors-in-Chief are Profs. Can Li and Tao Zhang.
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