Defluorinative Alkylation of Trifluoromethylbenzimidazoles Enabled by Spin-Center Shift: A Synergistic Photocatalysis/Thiol Catalysis Process with CO 2 • .

We describe a catalytic strategy for direct single C(sp 3 )-F bond alkylation of trifluoromethylbenzimidazoles under a photoinduced thiol catalysis process. The CO 2 radical anion (CO 2 •- ) proved to be the most efficient single-electron reductant to realize such a transformation. The spin-center shift of the generated radical anion intermediate is the key step in realizing C-F bond activation under mild conditions with high efficiency.