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

Abstract

Organic halides are highly useful compounds in chemical synthesis, in which the halide serves as a versatile functional group for elimination, substitution and cross-coupling reactions with transition metals or photocatalysis1–3. However, the activation of carbon–fluorine (C–F) bonds—the most commercially abundant organohalide and found in polyfluoroalkyl substances (PFAS), or ‘forever chemicals’—is much rarer. Current approaches based on photoredox chemistry for the activation of small-molecule C–F bonds are limited by the substrates and transition metal catalysts needed4. A general method for the direct activation of organofluorines would have considerable value in organic and environmental chemistry. Here we report an organic photoredox catalyst system that can efficiently reduce C–F bonds to generate carbon-centred 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 PFAS and fluorinated polymers, a critical challenge in the breakdown of persistent and environmentally damaging forever chemicals. An organic photoredox catalyst system efficiently reduces C–F bonds, generating carbon-centred radicals for hydrodefluorination and cross-coupling reactions, enabling the general use of organofluorines as synthons and breaking down environmentally damaging forever chemicals.