Isothiazole or 1,2-thiazole is an organic compound containing a five-membered aromatic ring consisting of three carbon atoms, one nitrogen atom and one sulfur atom. In contrast to isomeric thiazoles, the two heteroatoms are in adjacent positions. The ring structure of isothiazoles is incorporated into larger compounds that are biologically active, such as the drugs ziprasidone and piperone. Isothiazoles are an important class of five-membered sulfur heterocyclic compounds that are widely used in medicinal chemistry and organic synthesis due to the unique properties of two electronegative heteroatoms in the 1,2-relationship.