Photocatalytic oxygenation of anthracenes and olefins with dioxygen via selective radical coupling using 9-mesityl-10-methylacridinium ion as an effective electron-transfer photocatalyst

Hiroaki Kotani, Kei Ohkubo, Shunichi Fukuzumi

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233 Scopus citations

Abstract

Visible light irradiation of the absorption band of 9-mesityl-10- methylacridinium ion (Acr+-Mes) in an O2-saturated acetonitrile (MeCN) solution containing 9,10-dimethylanthracene results in formation of oxygenation product, i.e., dimethylepidioxyanthracene (Me 2An-O2). Anthracene and 9-methylanthracene also undergo photocatalytic oxygenation with Acr+-Mes to afford the corresponding epidioxyanthracenes under the photoirradiation. In the case of anthracene, the further photoirradiation results in formation of anthraquinone as the final six-electron oxidation product, via 10-hydroxyanthrone, accompanied by generation of H2O2. When anthracene is replaced by olefins (tetraphenylethylene and tetramethylethylene), the photocatalytic oxygenation of olefins affords the corresponding dioxetane, in which the O-O bond is cleaved to yield the corresponding ketones. The photocatalytic oxygenation of anthracenes and olefins is initiated by photoexcitation of Acr+-Mes, which results in formation of the electron-transfer state: Acr•- Mes•+, followed by electron transfer from anthracenes and olefins to the Mes•+ moiety together with electron transfer from the Acr moiety to O2. The resulting anthracene and olefin radical cations undergo the radical coupling reactions with O 2•- to produce the epidioxyanthracene (An-O 2) and dioxetane, respectively.

Original languageEnglish
Pages (from-to)15999-16006
Number of pages8
JournalJournal of the American Chemical Society
Volume126
Issue number49
DOIs
StatePublished - 15 Dec 2004

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