Efficient solution phase synthesis of 2-(N-acyl)-aminobenzimidazoles

An efficient solution phase protocol for the synthesis of 2-(N-acyl)-aminobenzimidazoles is reported. The 2-(N-acyl)-aminobenzimidazole ring system was assembled using SNAr reactions, nitro group reduction, acylthiourea formation and cyclization with EDC. The acyl protected 2-aminobenzimidazole derivatives were obtained in high yield and purity without purification of intermediates or final products. This reaction sequence eliminates the use of highly toxic cyanogen bromide, a reagent commonly used to prepare the 2-aminobenzimidazole ring system.