Asymmetric Hydrogenation of Isoxazolium Triflates with a Chiral Iridium Catalyst

Ryuhei Ikeda, Ryoichi Kuwano

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

The iridium catalyst [IrCl(cod)]2–phosphine–I2(cod=1,5-cyclooctadiene) selectively reduced isoxazolium triflates to isoxazolines or isoxazolidines in the presence of H2. The iridium-catalyzed hydrogenation proceeded in high-to-good enantioselectivity when an optically active phosphine–oxazoline ligand was used. The 3-substituted 5-arylisoxazolium salts were transformed into 4-isoxazolines with up to 95:5 enantiomeric ratio (e.r.). Chiral cis-isoxazolidines were obtained in up to 89:11 e.r., with no formation of their trans isomers, when the substrates had a primary alkyl substituent at the 5-position. The mechanistic studies indicate that the hydridoiridium(III) species prefers to deliver its hydride to the C5 atom of the isoxazole ring. The hydride attack leads to the formation of the chiral isoxazolidine via a 3-isoxazoline intermediate. Meanwhile, in the selective formation of 4-isoxazolines, hydride attack at the C5 atom may be obstructed by steric hindrance from the 5-aryl substituent.

Original languageEnglish
Pages (from-to)8610-8618
Number of pages9
JournalChemistry - A European Journal
Volume22
Issue number25
DOIs
Publication statusPublished - Jan 1 2016

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Iridium
Hydrides
Hydrogenation
Catalysts
Isoxazoles
Atoms
Enantioselectivity
Isomers
Salts
Ligands
Substrates

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

Cite this

Asymmetric Hydrogenation of Isoxazolium Triflates with a Chiral Iridium Catalyst. / Ikeda, Ryuhei; Kuwano, Ryoichi.

In: Chemistry - A European Journal, Vol. 22, No. 25, 01.01.2016, p. 8610-8618.

Research output: Contribution to journalArticle

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