Bayer Aktiengesellschaft

Egon Kohler

Hermann Seifert

Peter Feyen

A simplified process for preparing the known insecticide 0,S-dimethylthiolphosphoric acid amide of the formula ##STR1## inexpensively, in high purity and with minimum waste water and gas which would have to be specially treated to avoid environmental pollution, comprises

Preparation of O,S-dimethyl-thiolophosphoric acid amide

A process for the preparation of an O,O-dialkyl-S-(N-methylcarboxamidomethyl)-thiolphosphoric acid ester of the formula ##STR1## in which R.sub.1 and R.sub.2 each independently is alkyl, comprising reacting a salt of N-methylcarboxamidomethyl-thiosulphuric acid with an O,O-dialkyl phosphorous acid of the formula ##STR2## in a suspension in the presence of an alkaline earth metal alcoholate, alkali metal carbonate or alkaline earth metal carbonate, e.g. magnesium methylate or ethylate, calcium methylate or ethylate, potassium carbonate, sodium carbonate, magnesium carbonate or calcium carbonate. Advantageously R.sub.1 and R.sub.2 each independently has up to 4 carbon atoms, the N-methylcarboxamidomethyl-thiosulphuric acid salt is an alkali metal salt and the reaction is carried out in ethylene chloride or chloroform at a temperature of about 10.degree. to 40.degree. C. in the presence of triethylamine as catalyst.

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Dormagen, Germany

Egon Kohler