Iridium-Catalyzed Hydrogenation of a Phenoxy Radical to the Phenol: Overcoming Catalyst Deactivation with Visible Light Irradiation

Junho Kim, Yoonsu Park, Paul J. Chirik

Research output: Contribution to journalArticlepeer-review

Abstract

Piano-stool iridium hydride complexes bearing phenylpyridine ligands are effective precatalysts for promoting the formation of element-hydrogen bonds using H2 as the stoichiometric H-atom source. Irradiation with blue light resulted in a profound enhancement of catalyst turnover for the iridium-catalyzed hydrogenation of the aryloxyl radical 2,4,6-tBu3-C6H2O to the corresponding phenol. Monitoring the progress of the reaction revealed the formation of an iridium 3,3-dimethyl-2,3-dihydrobenzofuranyl compound arising from two C-H activation events following the proton-coupled electron transfer (PCET) step. Under thermal conditions, this compound was inactive for catalytic aryloxide hydrogenation, representing a deactivation pathway. Irradiation with blue light under H2 released the free heterocycle and regenerated the piano-stool iridium hydride precatalyst, establishing a pathway for catalyst recovery and overall enhanced turnover.

Original languageEnglish (US)
Pages (from-to)19582-19592
Number of pages11
JournalInorganic Chemistry
Volume62
Issue number48
DOIs
StatePublished - Dec 4 2023

All Science Journal Classification (ASJC) codes

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry

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