<unk>  is a nitrogen-containing heterocycle derived from imidazole. The ring contains an imine bond, and the carbons at the 4 and 5 positions are singly bonded, rather than doubly bonded for the case of imidazole.<unk> s are structurally related to guanidines and amidines.
Like imidazole,<unk> -based compounds have been used as N-heterocyclic carbene ligands on various transition metals. It is found in the commercially available second generation Grubbs' catalyst.
Imidazoline
Tolazoline
Tymazoline
Oxymetazoline
Tramazoline
Naphazoline
Oxymetazoline hydrochloride
Moxaverine