0.23 g of an 80% strength by weight suspension of sodium hydride in mineral oil was added at 23° C. to 25 ml of anhydrous dimethylformamide. The mixture was then treated dropwise with a solution of 2.50 g of 5-(3-chloro-5-trifluoromethylpyridin-2-yl)-1-(1-methylethyl)benzimidazol-2-one in 25 ml of dimethylformamide and, after stirring for 15 minutes, with 1.05 g of methyl iodide. After stirring for 6 hours, the reaction mixture was poured into 300 ml of ice water. The aqueous phase was extracted three times with 100 ml of tert-butyl methyl ether each time, after which the combined organic phases were washed twice with 50 ml of water each time, dried over sodium sulfate and concentrated. Chromatography on silica gel using cyclohexane/ethyl acetate (4:1) as the eluent gave 2.1 g of colorless crystals. Yield: 75%; m.p.: 108-109° C.
