Benzyltriethylammonium tetrathiomolybdate, [BnEt3N]2MoS4, has been used successfully to effect ring opening of aziridines in a regiospecific and stereospecific manner under mild reaction conditions without the use of Lewis acid catalyst. Utility of this reagent in tandem and multistep processes in a one-pot operation for the synthesis of various novel sulfur heterocycles in very good yield is also reported.