Access to 8-Azachromones via Activation of C-H in N-oxides.

A concise and practical synthetic method has been developed for 8-azachromones, including 8-azaflavones, which have emerged as a promising class of compounds. Using commercially available nicotinates as the starting material, 8-azachromones were obtained in only three steps. The key intramolecular O-arylation reaction was achieved by nucleophilic attack of enolates to C2 of N-oxides under PyBrop or Ac2O activation conditions. These studies provide the basis for the access to 8-azachromones, enabling future work including the discovery and development of novel chromonoid drugs or other functional materials.