3314-30-5

5466-57-9

3314-30-5

General procedure for the synthesis of 1H-benzimidazole-2-carbaldehyde from 2-(dichloromethyl)-1H-benzo[d]imidazole: 15 mL (276 mmol, 6.6 eq.) of concentrated sulfuric acid was slowly added dropwise to a reaction vial containing 8.40 g (41.8 mmol) of 2-(dichloromethyl)-1H-benzo[d]imidazole (Compound L5), and the formation of yellow bubbles was observed. After completion of dropwise addition, stirring was continued for 10 min to ensure complete dissolution of compound L5. Subsequently, the reaction mixture was heated in an oil bath at 80 °C for 1 h. The heating was stopped after completion of the reaction. After the reaction mixture was cooled to room temperature, 150 mL of ice water was added and the pH was adjusted with 4 N NaOH aqueous solution to 7. At this point, a yellow solid precipitated from the solution. The solid product was collected by filtration and dried to give 5.21 g of 1H-benzimidazole-2-carbaldehyde (compound L6) in 85.3% yield.