Catalytic photoinduced deoxygenation via B(C₆F₅)₃-enabled oxygen atom transfer for aromatic C-H amination of alkylarenes.

Abstract

The catalytic deoxygenation of N - OH bonds to generate N-centered radicals remains a significant challenge due to the high bond dissociation energy and reliance on stoichiometric auxiliaries or activators. Herein, we report a B(C₆F₅)₃-catalyzed photoinduced deoxygenation strategy that enables direct aromatic C(sp²)-H amination of alkylarenes using N-hydroxyphthalimides (NHPIs) as nitrogen sources. Mechanistic studies reveal that the in situ formation of a PhthN-O - B(C₆F₅)₃ anion intermediate facilitates an unusual energy transfer (EnT)-mediated N - O bond homolysis, generating a phthalimidyl radical (PhthN•) while regenerating the borane catalyst. This method overrides the conventional preference for benzylic C - H oxidation, achieving exclusive aromatic C - H amination with broad substrate scope, including electron-rich/poor alkylarenes, heteroarenes, and biomolecules. The catalytic protocol operates under mild conditions, avoids stoichiometric organic auxiliaries/activators, and produces H₂O as the sole byproduct, thus, making it a promising option to supplant existing strategies for arene amination. Applications in late-stage functionalization of pharmaceuticals and the synthesis of a nilotinib precursor highlight its synthetic utility. This study establishes B(C₆F₅)₃ as a versatile catalytic oxygen atom transfer (OAT) reagent in photochemistry, opening avenues for sustainable radical generation.