The tandem reaction of Morita–Baylis–Hillman (MBH) alcohols 1a–1l derived from acrylic nitrile with 2-aminobenzimidazole (2) in ionic iquid (IL) [BMIM]Cl/H2O without additional catalyst was developed for the efficient synthesis of benzimidazol[1,2-a]pyrimidin-7(8H)-imine compounds. The tandem reaction included aza-Michael addition and intramolecular addition of an amino group to the cyano group in one pot. The combination of ionic liquid and water was found to be the best reaction medium, which played a role for accelerating the tandem reaction.