Selective Oxygenation of Ring-Substituted Toluenes with Electron-Donating and -Withdrawing Substituents by Molecular Oxygen via Photoinduced Electron Transfer

Kei Ohkubo, Kyou Suga, Kohei Morikawa, Shunichi Fukuzumi

Research output: Contribution to journalArticlepeer-review

102 Scopus citations

Abstract

A ring-substituted toluene with an electron-withdrawing substituent, p-tolunitrile, is oxygenated by molecular oxygen to yield the corresponding aldehyde with tetrafluoro-p-dicyanobenzene as a photocatalyst under photoirradiation with an Hg lamp (λ > 300 nm). The oxygenation of a ring-substituted toluene with an electron-donating substituent, p-xylene, by molecular oxygen is also achieved with 10-methyl-9-phenylacridinium ion as a photocatalyst under visible light irradiation, yielding p-tolualdehyde exclusively as the final oxygenated product. Both the oxygenation reactions are initiated by photoinduced electron transfer from the ring-substituted toluene to the singlet excited state of the photocatalyst. The reason for the high selectivity in the photocatalytic oxygenation of various toluene derivatives by molecular oxygen is discussed on the basis of the photoinduced electron transfer mechanism that does not involve the autoxidation process (radical chain reactions). The reactive intermediates in the photocatalytic cycle are successfully detected as the transient absorption spectra and the electron spin resonance spectra.

Original languageEnglish
Pages (from-to)12850-12859
Number of pages10
JournalJournal of the American Chemical Society
Volume125
Issue number42
DOIs
StatePublished - 22 Oct 2003

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