PURPOSE: The sulfur atom-containing ring closure reaction of 1,3-dimercapto-2- dimethylaminopropane is conducted using sulfur to produce high-purity title compound useful as insecticide, nematocide and bactericide through simple operations in high yield.

CONSTITUTION: The reaction of novel 1,3-dimercapto-2-dimethylaminopropane, with sulfur, preferably more than 2mol per mol of the above compound, smoothly progresses in a solvent such as methylene chloride under mild conditions to give title compound readily. During the reaction the presence of a basic catalyst, especially an amine such as ethylamine is preferred. One mole of the sulfur employed is consumed for the oxidation or dehydrogeneration of the 1,3-dimercapto group and converted to hydrogen sulfied and the rest one mole of the sulfur joins in the ring formed. The use of sulfur helps the oxidation of 1,3-dimercapto group and sulfurization under mild conditions.