Dehydrogenation vs Oxygenation in Photosensitized Oxidation of 9-Substituted 10-Methyl-9,10-dihydroacridine in the Presence of Scandium Ion

Abstract

Photooxidation of 9-substituted 10-methyl-9,10-dihydroacridine (AcrHR) with oxygen occurs efficiently in the presence of 9,10-dicyanoanthracene (DCA) and scandium triflate [Sc(OTf)3] under visible light irradiation in oxygen-saturated acetonitrile (MeCN) to yield the 9-substituted 10-methylacridinium ion (AcrR+) and H2O2 or the 10-methylacridinium ion (AcrH+) and the oxygenated products of R such as ROOH, depending on the type of substitutent R. No DCA-photosensitized oxidation of AcrHR occurs in the absence of Sc3+ under otherwise the same experimental conditions. The observed selectivities for the C(9)−H vs C(9)−C bond cleavage of AcrHR in the DCA-photosensitized oxidation of AcrHR in the presence of Sc(OTf)3 agree with those for the cleavage of radical cations of AcrHR (AcrHR•+) depending on the type of substituent R. Such product selectivities, being consistent with the electron-transfer oxidation of AcrHR, combined with quantum yield determination, the 1O2 phosphorescence decay dynamics, and the dete...