Dispersion-Enhanced Nitrogen-Centered Photocatalysis of the Direct Hydrogen Atom Transfer

The development of structurally distinct and modular photocatalysts for direct hydrogen atom transfer (HAT) has emerged as a key frontier in radical-mediated C–H functionalization of strong carbon–hydrogen bonds. Despite the largely untapped potential across the fields of organic synthesis, medicinal chemistry, and materials science, few classes of direct HAT photocatalysts are currently known, and the approaches to enhancing their photocatalytic activity remain underdeveloped. We report herein the development of nitrogen-centered direct HAT photocatalysts based on the acridine framework, which leverage a C9-ortho-biaryl substituent for enhancing the photocatalytic activity through stabilizing dispersion interactions with the substrate as the key steering effect. The acridine direct HAT photocatalysis enables an array of carbon–carbon and carbon–heteroatom bond-forming reactions in diverse structural and experimental settings, including cryogenic conditions. It also provides a blueprint for enhancing the photocatalytic activity of direct HAT catalysts by leveraging photocatalyst–substrate dispersion interactions.