Solvent-Free Photooxidation of Alkanes by Dioxygen with 2,3-Dichloro-5,6-dicyano-p-benzoquinone via Photoinduced Electron Transfer

Kei Ohkubo, Kensaku Hirose, Shunichi Fukuzumi

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

Photooxidation of alkanes by dioxygen occurred under visible light irradiation of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) which acts as a super photooxidant. Solvent-free hydroxylation of cyclohexane and alkanes is initiated by electron transfer from alkanes to the singlet and triplet excited states of DDQ to afford the corresponding radical cations and DDQ⋅−, as revealed by femtosecond laser-induced transient absorption measurements. Alkane radical cations readily deprotonate to produce alkyl radicals, which react with dioxygen to afford alkylperoxyl radicals. Alkylperoxyl radicals abstract hydrogen atoms from alkanes to yield alkyl hydroperoxides, accompanied by regeneration of alkyl radicals to constitute the radical chain reactions, so called autoxidation. The radical chain is terminated in the bimolecular reactions of alkylperoxyl radicals to yield the corresponding alcohols and ketones. DDQ⋅−, produced by the photoinduced electron transfer from alkanes to the excited state of DDQ, disproportionates with protons to yield DDQH2.

Original languageEnglish
Pages (from-to)2255-2259
Number of pages5
JournalChemistry - An Asian Journal
Volume11
Issue number16
DOIs
StatePublished - 19 Aug 2016

Bibliographical note

Publisher Copyright:
© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Keywords

  • electron transfer
  • oxygenation
  • photoredox catalysis
  • quinone
  • radical

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