l-Proline Promoted Ullmann-Type Coupling Reactions of Aryl Iodides with Indoles, Pyrroles, Imidazoles or Pyrazoles

The Ullmann-type coupling reactions of aryl iodides and several nitrogen heterocycles occur at 80-90 °C with l-proline as additive, giving N-arylpyrroles, N-arylindoles, N-arylimidazoles, and N-pyrazoles in good to excellent yields.