Triethylamine → 3,3-Dimethyl-4-fluoro-1-methylthio-2-hydroximino-butane

99 g (0.6 mol) of 3,3-dimethyl-4-fluoro-1-methylthiobutan -2-one, 46 g (0.66 mol) of hydroxylamine hydrochloride and 66.7 g (0.66 mol) of triethylamine in 300 ml of ethanol were heated under reflux for 6 hours. The solvent was then removed in vacuo, the residue was partitioned between methylene chloride and water and the methylene chloride phase was separated off and dried with sodium sulphate. After distilling off the solvent, the residue was distilled in vacuo. 80 g (75% of theory) of 3,3-dimethyl-4-fluoro-1-methylthio-2-hydroximino-butane of boiling point 133° C./13 mm Hg were obtained. ##STR31## 78 g (0.43 mol) of 3,3-dimethyl-4-fluoro-1-methylthio-hydroximinobutane were dissolved in 300 ml of methylene chloride, and 26 g (0.46 mol) of methyl isocyanate were added dropwise. During this addition, the temperature of the reaction solution rose to about 35° C.