Ketones as ideal photocatalysts for decarboxylative fluorination and a competition with C(sp3)-H fluorination

Abstract

Fluorinated molecules are widely used in drug discovery and materials science. However, the efficient construction of a C(sp³)–F bond from diverse carboxylic acids with a promising low-cost photocatalyst to replace expensive metal catalysts remains a significant challenge. Herein, we present a cost-effective, metal-free, and highly efficient photocatalytic approach for the direct decarboxylative fluorination of aliphatic carboxylic acids and diacids via photoexcited aliphatic ketones. This reaction (milligram to gram scale) can be achieved in just a few minutes with low-power irradiation using a broad range of wavelengths, spanning from visible to ultraviolet light. Our investigation revealed that photoexcited ketones, commonly employed as hydrogen atom transfer (HAT) catalysts for various C(sp³)–H bond functionalizations, exhibit a distinct preference for single-electron transfer (SET) in the decarboxylation of aliphatic carboxylic acids when combined with Selectfluor and Na₂HPO₄.