To a suspension of 3-(3-trifluoromethylpyridin-2-yl)aniline (200 mg), N,N′-bis(tert-butoxycarbonyl)thiourea (278 mg) and diisopropylethylamine (0.336 ml) in dichloromethane (10 ml) was added 1-methyl-2-chloropyridinium iodide (279 mg), and the mixture was stirred for 16 hours. The mixture was diluted with ethyl acetate, washed with water and brine, dried over magnesium sulfate and evaporated under reduced pressure. The residue was purified by column chromatography (silica gel 30 g, n-hexane:ethyl acetate=4:1) to give N,N′-bis(tert-butoxycarbonyl)-N″-(3-(3-trifluoromethylpyridin-2-yl)phenyl)guanidine (234 mg).
