Chiral 2-Aminobenzimidazole as Bifunctional Catalyst in the Asymmetric Electrophilic Amination of Unprotected 3-Substituted Oxindoles

Molecules. 2018 Jun 6;23(6):1374. doi: 10.3390/molecules23061374.


The use of readily available chiral trans-cyclohexanediamine-benzimidazole derivatives as bifunctional organocatalysts in the asymmetric electrophilic amination of unprotected 3-substituted oxindoles is presented. Different organocatalysts were evaluated; the most successful one contained a dimethylamino moiety (5). With this catalyst under optimized conditions, different oxindoles containing a wide variety of substituents at the 3-position were aminated in good yields and with good to excellent enantioselectivities using di-tert-butylazodicarboxylate as the aminating agent. The procedure proved to be also efficient for the amination of 3-substituted benzofuranones, although with moderate results. A bifunctional role of the catalyst, acting as Brønsted base and hydrogen bond donor, is proposed according to the experimental results observed.

Keywords: asymmetric catalysis; benzimidazoles; electrophilic amination; organocatalysis; oxindoles.

MeSH terms

  • Amination
  • Benzimidazoles / chemistry*
  • Carbon-13 Magnetic Resonance Spectroscopy
  • Catalysis
  • Chromatography, High Pressure Liquid
  • Indoles / chemistry*
  • Oxindoles
  • Proton Magnetic Resonance Spectroscopy
  • Stereoisomerism


  • Benzimidazoles
  • Indoles
  • Oxindoles
  • 2-oxindole
  • 2-aminobenzimidazole