Palladium-catalyzed annulation of allenes with indole-2-carboxylic acid derivatives: synthesis of indolo[2,3-c]pyrane-1-ones via Ar-I reactivity or C-H functionalization

J Org Chem. 2012 Aug 17;77(16):6959-69. doi: 10.1021/jo301149s. Epub 2012 Aug 9.

Abstract

Two methodologies, one involving Ar-I reactivity and the other through C-H functionalization, for the formation of indolo[2,3-c]pyrane-1-ones via the corresponding allenes, are presented. A highly efficient approach to indolo[2,3-c]pyrane-1-one derivatives through the Pd-catalyzed regioselective annulation of allenes with 3-iodo-1-alkylindole-2-carboxylic acids is described. This method is fairly general for a wide range of allenes affording the respective indolo[2,3-c]pyrane-1-ones in good to excellent yields. In addition, a Pd(II)-catalyzed oxidative coupling of indole-2-caboxylic acid derivatives with allenes via direct C-H functionalization to afford the corresponding indolo[2,3-c]pyrane-1-ones in moderate to good yields has been developed.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkadienes / chemistry*
  • Carbon / chemistry
  • Carboxylic Acids
  • Catalysis
  • Crystallography, X-Ray
  • Hydrogen / chemistry
  • Indoles / chemical synthesis*
  • Indoles / chemistry
  • Magnetic Resonance Spectroscopy
  • Oxidation-Reduction
  • Palladium / chemistry*

Substances

  • Alkadienes
  • Carboxylic Acids
  • Indoles
  • indole-2-carboxylic acid
  • Palladium
  • Carbon
  • Hydrogen