Abstract
The reaction of dimethyl acetylenedicarboxylate with thioureas was re-investigated to examine the structure of the products previously recorded in several papers without definite evidence. By chemical reactions and spectroscopic data the five-membered structure, 2-imino-4-thiazolidone (II), was given to the products, contrary to the previously proposed six-membered structure, 2, 3-dihydro-1, 3-thiazin-4-one.
