Studies on Mesoionic Compounds. XII. Synthesis of 1, 2, 3-Thiadiazolium-4-aminide Derivatives and Their Characterization

New mesoionic heterocycles, 1, 2, 3-thiadiazolium-4-ethoxycarbonylaminides (9 and 10), were prepared by alkylation of 1, 2, 3-thiadiazoles (5) followed by treatment with base. Compound (9) was hydrolyzed to the hydrochloride of the corresponding 4-imine derivative (13), which was converted to the 4-oxo analog (16) via N-nitrosation.