Visible-Light-Induced Transition-Metal-Free Redox-Neutral Carboxylation of Remote Benzylic C(sp 3 )-H Bonds via 1,5-Hydrogen Atom Transfer.

The direct carboxylation of the benzylic C-H bonds under mild conditions is of great importance and is quite challenging. Herein, we report an approach for the carboxylation of remote benzylic C(sp 3 )-H bonds by integrating the redox-neutral visible-light photoredox catalysis and the nitrogen-centered 1,5-hydrogen atom transfer. The chemical transformation progresses via consecutive single electron transfer, 1,5-hydrogen atom transfer, formation of benzylic carbanion, and nucleophilic attack on the CO 2 steps, thereby enabling access to the desired carboxylation products with moderate to high yields. We also endeavor to recover the CO 2 groups generated in situ intramolecularly to achieve carboxylation under a nitrogen atmosphere, resulting in moderate yields of corresponding carboxylation.