Heterocycles are cyclic chemical compounds with ring-forming atoms of at least two different chemical elements. In most cases, one of these chemical elements is carbon. Other common elements contained in heterocycles are nitrogen, sulfur, or oxygen. Heterocycles can have aromatic character, in which case they are also referred to as heteroaromatics.
Due to the diversity of heterocyclic compounds and their structural diversity, they can be divided into different subclasses. For the three- to seven-membered ring systems, subgroups with their own basic bodies are distinguished in each case.
Heterocyclic compounds are of great importance for many basic building blocks of bioorganic and bioinorganic chemistry (DNA, cytochromes, cobalamins, hemoglobin, proteinogenic amino acids such as histidine or proline, etc.). In particular, nitrogen-containing compounds play an important role.
In preparative chemistry, heterocyclic substances often play an important role as solvents or auxiliary bases for initiating organic or inorganic reactions.