Treatment of 3-(methylsulfanyl)aniline (I) with cyanogen bromide affords the cyanamide (II), which is further N-alkylated with iodomethane and NaH to afford (III). Subsequent condensation of cyanamide (III) with 2-chloro-5-(methylsulfanyl)aniline hydrochloride (IV) in refluxing chlorobenzene gives rise to the desired guanidine derivative.
The methylation of N-[3-(methylsulfanyl)phenyl]cyanamide (I) with C3H3-I and NaH in THF gives the methylated cyanamide (II), which is then condensed with 2-chloro-5-(methylsulfanyl)aniline (III) in refluxing chlorobenzene to afford the target labeled guanidine.