Green and Efficient Synthesis of 1, 2, 4-Triazolidine-3-thiones using Guanidine Hydrochloride as a Recyclable Catalyst under the Aqueous Condition

A rapid and highly efficient methodology for the synthesis of 1, 2, 4-triazolidine-3-thiones derivatives has been developed in the presence of a catalytic amount of guanidine hydrochloride using water as a solvent. The reaction of thiosemicarbazide with different aryl aldehydes resulted in the formation of title compounds in good yields (85-95%) with a convenient reaction time (20-30 min). The key advantages of this approach include shorter reaction time, energy efficiency, easy work-up procedure, and wide substrate scope tolerance. Furthermore, the catalyst was recycled without significant loss of its catalytic activity.