The reaction of 3,4-dichlorophenol (I) with 1,3-dibromopropane (II) by means of NaOH and tetrabutylammonium hydrogensulfate gives the corresponding phenol ether (III), which is condensed with N-acetylhydroxylamine (IV) by means of NaOH or KOH in an alcoholic solvent to yield the O-substituted acetylhydroxylamine (V). The hydrolysis of (V) with HCl in methanol affords the free O-substituted hydroxylamine (VI), which is finally condensed with N1-cyano-N3-isopropylguanidine (VII) in hot ethyl acetate. The intermediate N1-cyano-N3-isopropylguanidine (VII) has been obtained by reaction of sodium dicyanamide (VIII) with isopropylamine (IX) and HCl in a hot alcoholic solvent.