The reaction of 5-dimethylaminomethyl-2-furanylmethanol (I) with 2-mercaptoethylamine (II) by means of aqueous HCl gives 2-[[(5-dimethylamino-methyl-2-furanyl)methylthio]ethaneamine (III), which is then condensed with N-methyl-1-methylthio-2-nitrotheneamine (IV) by heating at 120 C. Compound (IV) is obtained by reaction of 1,1-bis(methylthio)-2-nitroethene (V) with methylamine in refluxing ethanol.