7.3 parts of 3-chloro-6-mercaptopyridazine are neutralised with 20 parts of
10% caustic soda solution, diluted with 60 parts of 50% ethanol, and heated
to 60°C. 7.5 parts of chloroacetic acid diethyl amide dissolved in 20 parts of
ethanol are added to this solution over a period of 10 min and the resulting
mixture is heated to 60°C for 30 min. The reaction solution is then cooled, the resulting crystallisate is removed by suction, and the filtrate is extracted with
ethyl acetate. The solvent is removed by evaporation and the concentration
residue is combined with the crystallisate. After two recrystallisations from
benzene, 11 parts of 3-chloro-pyridazine-6-mercaptoacetic acid diethyl amide,
having a melting point of from 139° to 140°C are yielded.
