Abstract 3, 4-Dimethyl-4H-1, 3, 4-thiadiazines, novel 8π heterocyclic systems, were prepared by cyclization of α-haloketones with 1, 2, 4-trialkylthiosemicarbazides. The desulfurization of the products afforded 5-imino-1, 2-dimethylpyrazoles by valence isomerization into thia-σ-homopyrazoles.
