90871-47-9

75-30-9

934-32-7

90871-47-9

General procedure for the synthesis of 2-amino-1-isopropylbenzimidazole from 2-iodopropane and 2-aminobenzimidazole: A mixture of 2-aminobenzimidazole (1.33 g, 10.0 mmol), 2-iodopropane (10.0 mmol), finely pulverized KOH (1.0 g) with anhydrous K2CO3 (2.0 g) in acetone (50 mL) was heated with stirring at refluxed for 3 hours. Upon completion of the reaction, the solvent was removed by distillation under reduced pressure. The residue was partitioned between water (100 mL) and dichloromethane (100 mL) and the aqueous phase was extracted twice more with dichloromethane. The organic phases were combined and dried with anhydrous Na2SO4. Removal of the solvent gave an oily or solid residue, which was treated with a small amount of ether to give 2-amino-1-isopropylbenzimidazole (8a-e,1-o) as a white solid, which could be purified by crystallization with an appropriate solvent. Initial purification by silica gel column chromatography [eluent ethyl acetate-acetone (1:1)] is required only for the synthesis of compound 8f to obtain the crystalline product.