A C₁-Homologative Trifluoromethylation: Light-Driven Decarboxylative Trifluoroethylation of Carboxylic Acids

The incorporation of fluorinated alkyl groups is a powerful strategy to fine-tune the physicochemical and biological properties of organic molecules. In particular, the trifluoroethyl (–CH₂CF₃) substituent offers a valuable C₁-homologated analogue of trifluoromethylated motifs, yet methods for its direct introduction at sp³-hybridized carbon centers remain scarce. Here we report a general and practical approach for the decarboxylative trifluoroethylation of aliphatic carboxylic acids under visible-light irradiation. The transformation proceeds via photoinduced generation of a carbon-centered radical that adds to a bench-stable sulfonyl hydrazone reagent derived from trifluoroacetaldehyde, followed by light-driven fragmentation to furnish the desired trifluoroethylated products. The reaction operates under mild conditions, exhibits broad substrate scope, including primary, secondary, and tertiary acids, and tolerates diverse functional groups. Conceptually, the process can be viewed as a C₁-homologative trifluoromethylation, offering a distinct retrosynthetic disconnection for the synthesis of trifluoroethyl-containing building blocks. Mechanistic studies combining experimental and computational analysis provide insight into the fragmentation behavior of the key alkylated sulfonyl hydrazide intermediate.