Reactions forming and recyclizing heterocycles

It has been shown that 1,3-thiazolidine-2,4-dione and 1,3-oxazolidine-2,4-dione react with hydrazine with a rearrangement of the ring to form a triazolinone ring. In each case, the reaction begins with the formation of an ionic adduct of hydrazine with the azolidinedione. On heating, the adduct undergoes decyclization (water catalyzes the process). The further course of the reaction is governed by the temperature and pH of the medium, which determine whether dehydration of the intermediate product with the formation of a triazolinone ring (in acid media) or rearrangement into a 1-acylsemicarbazide (at elevated temperatures) predominates. The influence of substituents in the thiazolidinone ring on the course of the reaction has been studied.For Communication I, see 1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 7, pp. 991–996, July, 1970.