Cationic DABCO-Based Catalyst for Site-Selective C-H Alkylation via Photoinduced Hydrogen-Atom Transfer

A series of hydrogen-atom transfer (HAT) catalysts based on the readily available and tunable 1,4-diazabicyclo[2.2.2]-octane (DABCO) structure was designed, and their photoinduced HAT catalysis ability was demonstrated. The combination of our HAT catalyst with an acridinium-based organophotoredox catalyst enables efficient and site-selective C-H alkylation of substrates ranging from unactivated hydrocarbons to complex molecules. Notably, a HAT catalyst with additional substituents adjacent to a nitrogen atom further improved the site selectivity. Mechanistic studies suggested that the N-substituent of the catalyst plays a crucial role, assisting in the generation of a dicationic aminium radical as an active species for the HAT process.