58533-15-6

General method: 2-chloro-1H-benzimidazole (3.04 g, 20 mmol) was dissolved in anhydrous N,N-dimethylformamide (DMF, 15 mL) at 0 °C. Sodium hydride (NaH, 60% dispersed in mineral oil, 0.91 g, 22.7 mmol) was slowly added to this solution and the reaction mixture was stirred at 0 °C for 1 hour. Subsequently, ethyl bromide (21.6 mmol) was added dropwise. The reaction mixture was gradually warmed to room temperature and stirred overnight. Upon completion of the reaction, the mixture was poured into water (50 mL) and stirring was continued for 1 hour. The precipitate was collected by filtration, washed well with water and dried under vacuum to afford the target products 2-chloro-1-ethyl-1H-benzo[d]imidazole (4a-d).

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[2] European Journal of Medicinal Chemistry, 2011, vol. 46, # 1, p. 417 - 422
[3] European Journal of Medicinal Chemistry, 2010, vol. 45, # 3, p. 909 - 914