Imidazoles, condensed, Chichibabin amination

Amines are insufficiently nucleophilic to react with most azoles which do not contain a ring oxygen, and the stronger nucleophile NH2 is required. When treated with amide ions, thiazoles can be aminated in the 2-position by NaNHa at 150 °C. Only TV-substituted condensed imidazoles such as 1-alkylbenzimidazole react in such Chichibabin reactions. Imidazoles are aminated by alkaline NH2OH. 

The Chichibabin reaction with imidazoles has been the subject of extensive study in the U.S.S.R. (82CHE1221). Criteria for successful amination require that the imidazole ring be condensed with an aromatic system at the 4-and 5-positions, and that the pyrrole nitrogen be substituted (Scheme 72) (73CHE88). Another requirement is that the heterocycle must have a pK, of at least 4.3 for heterogeneous aminations. The parent compound, imidazole, substituted in the 1-position, does not undergo the Chichibabin reaction. Even substituted imidazoles such as phenanthro[9,10-d] imidazole (204) do not aminate (73CHE88). 

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