Acceptorless Dehydrogenative Oxidation of Secondary Alcohols Catalysed by Cp*Ir-III-NHC Complexes

Gulcemal S. , Gulcemal D. , Whitehead G. F. S. , Xiao J.

CHEMISTRY-A EUROPEAN JOURNAL, vol.22, no.30, pp.10513-10522, 2016 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 22 Issue: 30
  • Publication Date: 2016
  • Doi Number: 10.1002/chem.201601648
  • Title of Journal : CHEMISTRY-A EUROPEAN JOURNAL
  • Page Numbers: pp.10513-10522
  • Keywords: acceptorless dehydrogenation, alcohols, carbenes, iridium, oxidation, OPPENAUER-TYPE OXIDATION, HETEROCYCLIC CARBENE COMPLEXES, HIGHLY EFFICIENT OXIDATION, BASE-FREE, LESS DEHYDROGENATION, HYDROGEN-PRODUCTION, AEROBIC OXIDATION, METAL-COMPLEXES, H ACTIVATION, LIGAND

Abstract

A series of new Ir-III complexes with carbene ligands that contain a range of benzyl wingtip groups have been prepared and fully characterised by NMR spectroscopy, HRMS, elemental analysis and X-ray diffraction. All the complexes were active in the acceptorless dehydrogenation of alcohol substrates in 2,2,2-trifluoroethanol to give the corresponding carbonyl compounds. The most active complex bore an electron-rich carbene ligand; this complex was used to catalyse the highly efficient and chemoselective dehydrogenation of a wide range of secondary alcohols to their respective ketones, with turnover numbers up to 1660. Mechanistic studies suggested that the turnover of the dehydrogenation reaction is limited by the H-2-formation step.