The synthesis and ring—Chain tautomerism of 1,2,4-triazolidine-3-thiones, 2-amino-1,3,4-thiadiazolines,and hexahydro-1,2,4,5-tetrazine-3-thiones (review)

This review concerns the cyclization of thiosemicarbazones and thiocarbhydrazones of carbonyl compounds leading to the title heterocycles. We examine the irreversible cyclization by the action of oxidizing agents or as the result of acylation or alkylation as well as the ring—chain tautomerism. The effect of the substitution and solvent on the equilibrium of the thiosemicarbazones with some of the possible heterocyclic tautomeric forms was examined. The usefulness of these data for predicting the results of their irreversible cyclization was discussed.Dedicated to Professor A. R. Katritzky on the occasion of his sixty-fifth birthday.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 991–1005, July, 1993.