1, 2, 4, 2H-Thiadiazine-3, 5 (4H, 6H)-dione-l, l-dioxide (I) has been synthesized via the sequence: sulfoacetic acid (111 1, chlorosulfonylacetic acid (V), ethyl sulfamylacetate (VII), carbethoxymethanesulfonylurea (VIb) and base-catalyzed ring closure of the last compound to I. The product I, which was characterized by analysis, neutralization equivalent arid infrared spectrum, is a stable, crystalline solid, resembling barbituric acid (11) in its ...