Photoredox Catalytic Trifluoromethylation and Perfluoroalkylation of Arenes Using Trifluoroacetic and Related Carboxylic Acids

Abstract

Summary: Trifluoroacetic acid (TFA) is among the most attractive trifluoromethylation reagents with respect to its low prices, ease of handling, and availability in large quantities. However, because of its exceedingly high oxidation potential, harsh conditions are required for the direct oxidation of TFA to the trifluoroacetate radical, which after prompt CO2 extrusion, affords the desired CF3 radical. Therefore, mild and efficient protocols for the direct conversion of TFA to the CF3 radical are still in high demand. Here, we report a mild and practical method that allows for the direct C–H trifluoromethylation, perfluoroalkylation, and chlorodifluoromethylation of (hetero)arenes using TFA and the related carboxylic acids. A diverse array of arenes and heteroarenes were successfully transformed into valued fluoroalkylated compounds. The combination of photoredox catalysis and a diaryl sulfoxide provides a platform for the facile generation of fluoroalkyl radicals from the corresponding fluoroalkyl carboxylic acids under mild conditions.

Keywords

• photoredox catalysis
• trifluoromethylation
• chlorodifluoromethylation
• perfluoroalkylation
• trifluoroacetic acid
• sulfoxide