Abstract 1, 2, 3-Thiadiazole-4-carboxylic acid (IV) has been synthesized by oxidation of 5-(2- furyl)-1, 2, 3-thiadiazole-4-carboxylic acid (IIb), and converted via the acid chloride (V) to the amide (VI), ethyl ester (VII) and azide (IX). Rearrangement of the azide (IX) in ethanol led to ethyl N-(1, 2, 3-thiadiazol-4-yl) carbamate (X) and in benzene or toluene to a complex substance, possibly N, N, N-tris-(1, 2, 3-thiadiazol-4-yl)-isocyanurate (XI). Ethyl 5-phenoxy ...