A solution containing 75 mg of [5-(3,5-dichlorophenylthio)-3-methyl-1H-pyrazol-4-yl]-phenyl-methanone in 2 ml of dry N,N-dimethylformamide (DMF) at rt under nitrogen was treated with 12 mg of sodium hydride. The mixture was then stirred for 2 min. To the mixture was added 25 μl of 2-iodopropane. The mixture was then stirred for 20 min. To the mixture was added 2 ml of water and then the mixture was extracted with ethyl acetate three times. Combined extracts were washed with brine then dried over anhydrous magnesium sulphate, filtered and evaporated. The residue 7; was purified by flash chromatography on silica gel using diethyl ether hexane (1:7) for the elution to give 32 mg of [5-(3,5-dichlorophenylthio)-1-isopropyl-3-methyl-1H-pyrazol-4-yl]-phenyl-methanone as a colourless oil. Mass spectrum (ES) m/z 405[M+H]+.
