Oxidative con-PET Catalysis for Arene Functionalization

We report the first successful use of consecutive two-photon accumulation of visible light energy to obtain ultra-high oxidation potentials (> +3 V vs. saturated calomel electrode) enabled by a new class of rationally designed cyclic triarylamine photocatalysts. We demonstrate its practical and synthetic utility in a series of reactions of electron deficient arenes and fluoroarenes with N-nucleophiles. We identified that the photocatalytic reaction is initiated by the lowest excited state of the photocatalyst’s radical cation which abstracts an electron from the substrate only at non-diffusive/direct contact encounters, i.e. the omnipresence of substrate as co-solvent, since the excited radical cation lives only for ps. Neither pre-assembly nor a specific ‘anti-Kasha’ reactivity of a higher excited electronic state is observed. This method may serve as a promising basis for yet unexplored chemical reactions of substrates with very high oxidation potential and presents an attractive alternative to existing methods.