The acridone anion as a highly reducing visible-light photocatalyst.

Highly reducing photocatalysts enable the activation of strong chemical bonds under mild conditions. Here, we report that, upon visible-light excitation, deprotonated acridone generates a highly reducing excited state that activates (hetero)aryl halides, including chlorides, for C-B, C-P, C-S, and C-C bond formation, and, in combination with nickel catalysis, enables C-N bond formation. Mechanistic studies confirm that the excited-state acridone anion is capable of a single-electron transfer to aryl halides for bond activation.