Cobalt-catalyzed arylation of azole heteroarenes via direct C-H bond functionalization

Org Lett. 2003 Oct 2;5(20):3607-10. doi: 10.1021/ol035313o.

Abstract

[reaction: see text] We herein report a new cobalt-catalyzed method for arylation of azole heteroarenes, including thiazole, oxazole, imidazole, benzothiazole, benzoxazole, and benzimidazole. The direct arylation of thiazole and oxazole was achieved both with iodo- and bromoarenes as the aryl donors in the presence of cobalt catalyst [Co(OAc)(2)/IMes] and cesium carbonate, while imidazole required the use of zinc oxide as the base. A complete reversal of arylation from C-5 to C-2 was accomplished using the bimetallic Co/Cu/IMes system. A direct comparison of the new cobalt method and the previously developed palladium protocol revealed significant differences, in terms of both chemical yield and selectivity.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Azoles / chemistry*
  • Catalysis
  • Cobalt / chemistry*
  • Hydrocarbons, Aromatic / chemical synthesis*
  • Hydrocarbons, Aromatic / chemistry
  • Imidazoles / chemistry
  • Oxazoles / chemistry
  • Palladium / chemistry

Substances

  • Azoles
  • Hydrocarbons, Aromatic
  • Imidazoles
  • Oxazoles
  • Cobalt
  • Palladium
  • imidazole