Preparation of 2‐Aminopyridoimidazoles and 2‐Aminobenzimidazoles via Phosphorus Oxychloride‐Mediated Cyclization of Aminoureas.

The novel preparation of 2-aminopyridoimidazoles and 2-aminobenzimidazoles via the cyclization of (2-aminopyridin-3-yl)urea and (2-aminophenyl)urea substrates in the presence of phosphorus oxychloride is described. This methodology is demonstrated for a range of urea substrates with aminoimidazole products obtained in good yields and with excellent levels of purity.