Thiophene is a five-membered heterocyclic compound containing a sulfur heteroatom with the molecular formula C4H4S. Thiophene is aromatic and is very similar to benzene; electrophilic substitution reaction is easier than benzene, and it is mainly substituted at the 2-position. Thiophene ring system has certain stability to oxidant.
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.