Red-Light Photoredox C-H Alkylation Enabled by Catalytic NADH

NADH is an essential redox mediator in biology and biocatalysis, yet its catalytic use in non-enzymatic synthetic chemistry remains essentially unknown. Here we show that NADH can act as substoichiometric reductive-quencher in red-light photoredox catalysis, enabling a redox-neutral C(sp 2 )-H alkylation of heterocycles. This strategy avoids stoichiometric waste and leads to excellent yields and selectivity by suppressing overreduction. The reaction proceeds in air under mild, aqueous-compatible conditions and operates in complex biological media, establishing NADH as cofactor for artificial red-light photoredox catalysis under potentially biocompatible conditions.