This invention provides a low cost technique for synthesizing cyclic trithiocarbonates by a simple one step process from epoxides that can be conducted under atmospheric pressure. This synthesis can be depicted as follows: ##STR1##

wherein R represents a moiety selected from the group consisting of alkyl groups and aryl groups, wherein R represents a moiety selected from the group consisting of alkyl groups, aryl groups, and hydrogen atoms, and wherein R" represents a moiety selected from the group consisting of alkyl groups, aryl groups, and hydrogen atoms, wherein the R moiety and the R moiety can be bonded together to form a cyclic structure, with the proviso that R" represents a hydrogen atom if R represents an alkyl group or an aryl group. In this process carbon disulfide and a thiocyanate salt, such as potassium thiocyanate, are reacted with the epoxide in an ionic liquid, such as 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim] PF₆) in the presence of water to produce the cyclic trithiocarbonate.