Photocatalytic C–F bond activation in small molecules and polyfluoroalkyl substances

Abstract

Organic halides are highly useful compounds in chemical synthesis, where the halide serves as a versatile functional group for elimination, substitution, and cross-coupling reactions with transition metals or photocatalysis^1-3. However, the activation of carbon-fluorine bonds, the most commercially abundant organohalide and found in PFAS, or “forever chemicals”, are much rarer. Current approaches based on photoredox chemistry for activation of small molecule carbon-fluorine (C–F) bonds are limited by the substrates and transition-metal catalysts needed⁴. A general method for the direct activation of organofluorines would have significant value in organic and environmental chemistry. Here, we report an organic photoredox catalyst system that can efficiently reduce C–F bonds to generate carbon-centered radicals, which can then be intercepted for hydrodefluorination (swapping F for H) and cross-coupling reactions. This system enables the general use of organofluorines as synthons under mild reaction conditions. We extend this method to the defluorination of polyfluoroalkyl substances (PFAS) and fluorinated polymers, a critical challenge in the breakdown of persistent and environmentally damaging forever chemicals.