An Efficient Synthesis of Benzimidazole‐pyrazines via the Sequential Ugi/Hydroamination/Cyclization Reactions

Abstract This study reported an efficient two‐step method based on the sequential post‐Ugi hydroamination reaction for synthesizing a novel class of benzimidazole‐pyrazines with high yields. First, a Ugi fourcomponent reaction (Ugi‐4CR) is carried out using readily available starting materials, i. e., 1 H ‐benzo[d]imidazole‐2‐carboxylic acid, aldehydes, propargylamine, and isocyanides, in methanol at ambient temperature. Afterward, the Ugi products undergoes a sequential intramolecular hydroamination/cyclization reaction between a nitrogen of imidazole and alkyne functional group in aqua media in the presence of AuCl 3 as a catalyst to obtain benzimidazole‐pyrazine products. These heterocyclic compounds may have a potential to be utilized in designing modern drugs with desirable features.