Site-selective C–H difunctionalization of N-alkyl activated azaarenes via the synergistic catalysis of graphene oxide and visible light

Abstract

Strategies for site-selective C–H difunctionalization on N-alkyl activated azaarenes have attracted considerable attention as a powerful tool in heterocyclic chemistry. By employing graphene oxide (GO) as a heterogeneous cocatalyst, the visible light-induced site-selective difunctionalizations of pyridiniums/quinoliniums provided a distinct and straightforward synthetic route toward C4- and C2-selective phosphonation of the pyridinone/quinolinone/quinolone cores. Furthermore, the site-selectivity on quinoliniums could be successfully switched from C4 to C2 by changing the base and solvent. This coordination of catalysis systems drove the regioselective phosphonyl radical and phosphoryl anion addition to N-alkyl activated azaarenes, respectively, and subsequent oxidation with air as the terminal oxidant. In vitro antitumor studies showed that complex 3c participated in mitochondria-mediated pathways on the apoptosis of HeLa cells to 42.2% (21 μM). Phosphorus-based organocatalyst 4e, as one of the optical materials, offered efficient tuning of the emission and quantum yields.