Naphthyridine is a class of aromatic heterocyclic compounds whose chemical formula is C8H6N2. They consist of naphthalene bicyclic rings in which two carbon atoms are replaced by nitrogen atoms. There are ten isomers of naphthyridine, because naphthyridine has two benzene rings, has strong π-π conjugation, and has better luminescence properties. Common naphthyridines are 1,8-naphthyridines. There are many kinds of 1,8-naphthyridine derivatives, and they are widely used.
Oxazolines are five-membered heterocyclic compounds with one double bond. The double bond may be in one of three positions, so there may be three different oxazoline rings. The 2-oxazoline structure is the most common, and 3-oxazoline and 4-oxazoline exist mainly as laboratory research compounds. Oxazolines exist between oxazole and oxazolidine in terms of saturation.