A solution of 1-oxo-2,3,4,5-tetrahydro-1H-[1,4]diazepino[1,2-a]benzimidazole-8-carboxylic acid (Intermediate B, 103 mg, 0.42 mmol) and TBTU (149 mg, 0.46 mmol) in DMF (2 mL) is stirred for 10 min. 1-Ethyl-1H-benzimidazol-2-amine (68 mg, 0.42 mmol) and triethylamine (43 mg, 0.42 mmol) are added and the reaction is stirred at room temperature for 16 h. The reaction mixture is diluted with H2O. A yellow solid is formed that is filtered and washed with EtOAc and a small amount of methanol to afford the title compound (85 mg, 51%).
