Visible-Light-Induced Transition-Metal-Free Redox-Neutral Carboxylation of Remote Benzylic C(sp)-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)-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 steps, thereby enabling access to the desired carboxylation products with moderate to high yields. We also endeavor to recover the CO groups generated in situ intramolecularly to achieve carboxylation under a nitrogen atmosphere, resulting in moderate yields of corresponding carboxylation.