Imidazolines are a class of heterocycles derived from imidazoles by reduction of one of the two double bonds. Three isomers are known, 2-imidazoline, 3-imidazoline and 4-imidazoline. 2 and 3-imidazolines contain imine centers, while 4-imidazolines contain alkene groups. The 2-imidazoline group occurs in several drugs. Imidazolines are an important class of compounds found in many natural and medicinal products. These compounds are also used as intermediates in the synthesis of organic molecules. Furthermore, chiral imidazolines are widely used as organic catalysts for the synthesis of various natural and synthetic organic compounds.
Thiadiazoles are a subfamily of azoles. Structurally, they are five-membered heterocyclic compounds containing two nitrogen atoms and one sulfur atom, and two double bonds, forming an aromatic ring. Depending on the relative positions of the heteroatoms, there are four possible structures; these forms do not interconvert and are therefore structural isomers rather than tautomers. These compounds themselves are rarely synthesized and have no particular utility, however, compounds that use them as structural motifs are fairly common in pharmacology.
Benzoheterocycles are heterocycles which are fused with a benzene ring. Coumarone, thianaphthene, benzopyridine, isoquinoline, and dibenzopyridine all belong to this class of compounds.