4-Amino-5-chloro-2,1,3-benzothiadiazole (I) is reacted with CSCl2 to 5-chloro-4-isothiocyano-2,1,3-benzothiadiazole (II), which gives 4-[3-(2-aminoethyl)-2-thioureido]-5-chloro-2,1,3-benzothiadiazole (IV) with 1,2-diaminoethane (III). Cyclization in methanol in the presence of KOH/Pb(OAc)2 leads after 1 h at reflux to DS 103-282.